The Music Room
Home Hi-Fidelity Loudspeakers are in a general sense a key link into the musical realm. The most important single component in the audio chain, it very well may be. They are also the portal, the 'window' to the music. I tend to agree in a 'general' manner with this line of thought, bearing in mind that 'quality' must be evenly distributed throughout any audio system, not just in any particular area. Expect to spend some hundreds of dollars if you want good sound even if you DIY the speakers yourself.
Even a Bose 1-2-3 system, a killer application for those "family room blues", will set you back some serious money.
Loudspeakers convert the electrical energy coming from an amplifier device into sound pressure waves, we sometimes call music. This electro-mechanical power transfer is where it all happens. So, an audio amplifier's electrical energy is electromechanically converted into acoustical sound waves. Depending on the type of music, some refer to the end result as noise pollution.
There are many different types of Loudspeaker systems on the market today, and there probably will be some radically new designs tomorrow.
In a loosely categorized manner, I list below most of the common loudspeaker designs, yet there are new breakthroughs every year that don't fit into these categories and challenge the current state-of-the art.
Some loudspeaker systems may be a 'combination' of two or three of these types together.
Other speaker systems are so esoteric and beyond the scope of my comprehension such as Plasma Tweeters.
Here's a nice web site to start to read and understand what speaker types work well with Tube amplifiers and also what speakers are not as Tube Friendly as they may seem.
Here's another link that provides a web based speaker design calculator. This is good to play around with and get a feel for how most speakers operate.
This section of my web page is in no way an 'experts' view on Loudspeakers, I claim no pedigree in speaker design. Only my humble 2-way Red Oak speakers present my attempt to make a pair to suit my musical whims.
There are books that dedicate lots of effort in explaining the complex subject of Loudspeaker Design. Therefore, what I present below is my version of Loudspeakers in general, not a reference to any detail.
I make no claims to the fact that "Magnepan" planar designs may be a better speaker than a "Quad ESL." Or that Bose 901's are anything but a very clever actively equialized design. In the end, it really should be up to you to decide what speakers best meet your musical needs.
Some love the Boom and Sizzle with Bass and Treble at MAX. Other's need that 'license-plate' shaking Bass. There seems to no limit to the human condition of playing with equalizers and tone controls. In the Hi-End snob world, simplicity and high cost dominates the speaker landscape.
In no single area is there more controversy than with the effects of the complex psycho-acoustic relationship between man and speaker. Probably lots more complicated than the millennial man and dog relationship, speakers are love-hate centric components.
What I do know, for a fact is that matching tube amps to speakers in a synergistic relationship is not a trivial task. On the one hand, a Dynaco ST-70 and a pair of Vintage Bose Model 301 Speakers may just fill a musical need. But the same Dynaco ST-70 powering a pair of low efficiency "Thiel's" may not be the best application, even in the user likes the results while the tube amp suffers.
Of all of our known senses, the most under-estimated is our sense of hearing. But as with any sense, and let's take the example of sight, one person may see a dark-blue color, while to another person the color is black.
Imagine having to train people to distinguish colors. Well something similar happens when we listen to live music. Another happens when we listen to reproduced music. Not every event will provide accuracy and the best sound. Not every person hears the same thing.
I've been to live show's where the musician has obviously had some issues with equipment, hum, distortion, etc. While other live events sound eerie, such as Live Pink Floyd or a Symphony Orchestra. Part of being in 'goose bump' land. Reproducing music at home requires a speaker system offering dynamic range, good transient response, a benign reactive load and other known positives.
Some people prefer high efficiency while others gravitate towards high powered amplifiers and lower efficiency speaker systems. Once again no right's and no wrongs... just the way in that Audio and Electronics works today.
Are people concerned about paying/downloading and losing their music to a MP3 crash? Apparently not. Society will continue to surprise us in the manner of people and how they want their goods and services delivered. I for one remain a traditionalist. No way I will invest in downloaded music unless I can have some means to verify the fidelity and securely archive for future reference.
There will be arguments bearing all kinds of pre-conceived notions about what Hi-Fi actually means. Well to most of us, we really don't care to enter this area of debate, there are lot's of forums for that kind of activity. I find these entertaining. Also the Stereophile reader letter's are great. Here you can find everything from praise to utter dismay.
Here are some general loudspeaker categories:
Type of speaker system based on a sealed airtight enclosure principle. These speaker systems exhibit less acoustic efficiency as compared to other systems. Another characteristic of an acoustic suspension design is it's simplicity to achieve good results for the do-it yourself audio enthusiast. Bear in mind that the Low frequency drivers (woofers) must have an EBP - Efficiency Bandwidth Product of 50 or less in order to function their best in a sealed enclosure. EBP is calculated by dividing two values from the woofer's specifications sheet. EBP = fs/Qes.
This type of loudspeaker system utilizes a tuned port or opening of the enclosure. Not as simple to optimize as an acoustic suspension design, Bass reflex speakers achieve higher efficiencies and also create the impression of more bass from smaller diameter drivers and smaller enclosures. The theory behind Bass reflex enclosures was described by 'Thiele-Small' and the parameters one can calculate for a given set of design objectives. Woofer's best suited to Bass reflex enclosures often have an EBP of greater than 50, more often closer to 100. The same formula applies : EBP = fs/Qes.
Another less commonly seen but potentially much better solution are Transmission Line, TL enclosures. Low frequency drivers suited for Transmission line enclosures are not easily predicted from mathematical theory alone, empirical testing seems to be the best method.
A Transmission line enclosure is based on a similar principle as that of a large brass musical instrument. One constructs and fills with plenty of stuffing and wadding a long, convoluted tunnel that often tapers from a large to small area along it's length. The transmission line tunnel may be 6' to 25' long, thus these cabinets can tend to be bulky.
Due to the physical requirements of such TL enclosures, the tunnel is folded upon itself a number of times reducing the size of the enclosure. No fixed mathematical theory for TL design exists today, but there are successful attempts have been made to model this type of enclosure, one of them by a gentleman from Finland.
Transmission line speakers are characteristically known for quality bass reproduction with a sound that is not congested, as in some box speakers. As the back wave is systematically channeled down the length of the transmission line, an enhancement of the drivers low end response results that sounds very good, much better than most sealed or ported enclosures.
Mr. Irving "Bud" Fried of http://www.friedproducts.com is a pioneer on this type of design and his products should always be given a serious audition.
Often heavily misunderstood and expensive, Electrostatic speaker systems are characterized by an open, airy sound that is also scales to the size of the musical presentation, but tend to be directional with a very small sweet spot. A piano not only sounds correct but 'feels' like it's really there. Electrostatic loudspeakers are, as mentioned before, often expensive.
Economical models start at $2KUSD the pair and can quickly empty your wallet. Smaller electrostatic models from http://www.martinlogan.com utilize a separate Sub-Woofer driver to fill-in the missing lower octaves they are unable to reproduce, unless you purchase the largest models. Most electrostatic speakers have limited LF extension so home brewer's may want to match their Sub-woofers to a home made design.
The driven element consists of a membrane impregnated with a metallic compound suspended in between two large metal plates or plate-like surfaces, similar to a capacitor's design. Electrostatic speakers require an active electronics interface package or module that 'converts' and 'transforms' audio power into a useable signal at several thousand volts, very low current and high impedance.
The electrostatic element is a 'stretched' membrane between two charged plates that is excited into oscillation by electrostatic principles. Owing to the time varying Electric Field between the plates, the membrane oscillates and creates music.
Typical frequency responses for an affordable electrostatic speaker system is 35-30 KHz, the range from 35 Hz to 200 Hz is often handled by an integral powered sub-woofer. Electrostatics make a very interesting Home Brew project, but the degree of difficulty and availability of materials make this a whole degree of difficulty higher than a traditional box speaker.
The Bass Horn enclosure is probably one of the oldest designs. Such an enclosure is characterized by a large cabinet with internal divisions making a tunnel that causes the rear wave of the Woofer or LF driver to channel down and enhance the low frequency response at a opening called a port or slot. Bass horn enclosures are characterized by high efficiency and a very low "WAF" - Wife Acceptance Factor.
Bass Horns make use of full range, high efficiency driver units such as Lowther or Fostex, maybe also Jordan-Watts. These are then mounted on the very large bass horn cabinets front, rear, side, or top. Sometimes multiple drivers are placed in Parallel or series increasing the sound radiating cone area.
Often criticized for having 'colored' sound, bass horn enclosures are the favorite of Orchestral and Large Ensemble music fans. They have an uncanny ability to fill the room with sound from multiple groups of 'real' instruments.
Bass horns are not for the detail minded person, and their application almost always has a Tube Amplifier as a preferred source of power, owing to their typically high efficiencies on the order of +98 dB SPL or higher, that mate well with almost any tube amp no matter how small.
Some nice bass horn designs can be found at this web site:
Rather unusual in the audio community, a limited number of companies design and market this type of loudspeaker. Ribbon type speakers such as a 'Maggie' from Magnepan utilize a ribbon element that is connected to a special interface circuit whose purpose is to 'excite' the ribbon into vibration.
Not known for having high efficiency, Ribbon speakers are often mated to high power solid state or tube type amplifiers. Ribbon speakers can be expensive and also difficult to service, often requiring a trip back to the factory for proper repair and restored operation.
Some people will love them the first time they hear a Ribbon type speaker and swear that nothing else comes close.
This design is very much older that any other design, owing to it's sheer simplicity. The infinite baffle design is basically that of a driver or set of drivers flush mounted on large wall or very, very large wood panel. Infinite baffle speakers are space consuming designs, often implemented as built-in to the wall of a home. The sound of a well setup infinite baffle system can be described as open, airy and as appearing to come from everywhere. The problem is that they are not practical due to size and installation constraints.
Actively radiates only from the front or the rear of the cabinet, not both.Di-pole
Actively radiates from both the front and the rear of the cabinet.Planar
Radiates equally in both planes of the speaker, such as Electrostatic and Ribbon types.Omnidirectional
Radiates in a full 360 degree pattern, seen in rare but unique applications, mostly of German manufacture.Direct/Reflecting
Dr. Amar Bose patended his version of this type of design that radiates in multiple sound planes simultaneously. Some early models came equipped with control vanes to 'steer' the High Frequency sound. Early Bose speakers employed multiple medium and high frequency drivers pointing in several directions. Bose Direct/Reflecting Speaker Technology requires a sound room with flat reflecting surfaces that properly allow the speakers to reflect the medium and high frequency content. Made famous by the 901 Series Models, today Bose has grown into a highly commercialized company and is successful at marketing technology with a new computerized twist. I have not actually seen Dr. Bose's engineering calculations but I do know that he must employ Control State-Matrix Control theory to model loudspeaker systems, hence the term 'Acousti-Mass' based on the theory of Electro-Mechanical analogues. A clever and successful designer, Dr. Bose will probably be inducted into the Audio Hall of Fame if not already.
Loudspeakers must match to the owner and the amplifier. Just as when we own a pet, some pets are a better match for certain lifestyles. In Loudspeakers the same principle applies. Therefore, we should stay away from generalizing about what a loudspeaker system may or may not give to a particular user based on reading alone.
It's best to focus on a listening test for the best overall sound quality within a particular room size. Some listeners want 'bass clarity', other want 'to die for' midrange, or yet many feel that 'extended highs' are the ticket to better sound. In my experience, it's all about quality of materials and overall design execution, not any particular thing or sound.
If one cannot enjoy music without the rattling of windows, 8-inch Woofers are no place to look. Other folks may prefer a 'sizzling' top end and 'recessed' midrange with a somewhat 'bloated' bass response. It all depends of the quality of the particular loudspeaker design and the owners musical tastes in music. What may be perfect sound to a given reviewer may not satisfy another audio enthusiast.
Music and the experience that it imparts is as varied as the size and shape of our auditory canal inside our ears. Once again, I have to reiterate that most people perceive music as improved, only when the Treble and Bass controls are fully clockwise or 'floored' so as to describer this phenomenon. If that is their particular wish, be my guest, absolutely. Yet this is not what the recording engineer or artist intended you to hear, despite your preference.
Almost all average folks seem to agree that with the amplifier tone controls placed near or at their center position, the experience 'lacks' something they feel important to have. My opinion on this is that we have 'trained' the majority of consumers to expect music to contain extreme Low Frequency and High Frequency content. In other words sonic artifacts that are not in the original recording. This is sad indeed, but mostly true. Over and over again I have to center Tone controls on Rental Cars, Boom boxes, Hi-End stereo systems, etc. to be able to tolerate the music. The audio equalizer is one such device that allows people to 'butcher' to their hearts content. If you feel that you need an audio equalizer, don't buy exotic components, it's a waste of money. Get an economical setup and then tweak until happy. Nevertheless Hi Fidelity is something else.
As midrange performance from Class B solid state amplifiers over the last +40 years has not equaled most Tube-Amp style midrange 'magic', people feel compelled to Boost the Low and High frequencies to compensate for a ragged and hard to listen to midrange from the average Solid State amp and speaker system. This is what I believe to be the fundamental reason for people boosting frequency extremes. This is a simple way to mask problems in the audio chain and speaker, not solve them.
Make sure that you audition all Loudspeakers with the tone controls at center and as close to the same amp you will use. This way you can accurately determine the virtues and deficiencies of each design. An analogy would be to see a woman without makeup before judging her physical beauty or a guy in his bathing suit to make sure what that beer belly is really like, maybe just the same as six cold six pack of beer.
Also very important, is the construction of your home listening area to the sound quality that any given set of speakers can deliver. If your home structure is framed sheetrock, with wooden floors, carpet and curtains.. you may want a brighter sounding loudspeaker system. If the home is concrete block, with poured-in-place slab flooring and lots of concrete blocks and rebar/stone, then the softer 'British' sounding speaker may be best choice. American sound is characterized by 'brighter' highs and ever so slightly under-damped lows. The British sound is characterized by laid back yet smooth highs, almost to the point of being recessed and very tame, almost critically-damped lows for accurate but restrained bass performance.
One has to realize that most Loudspeaker Systems are heavily 'marked-up' in price, it's just a part of the business of making money off Particle board, Veneers, Wood, Screws, Fabric, Plastic, Glue gun goop and some real cheapo drivers. These are the run of the mill department store variants. But this condition also afflicts some so called boutique speakers as well.
We can spend a large sum of money and get the 'best' that we can afford, or can choose to spend the money on a good set of high quality parts and build the rest, not the best path unless the plans and results are cookbook and proven to perform.
We can save hundreds even thousands of dollars doing it this cookbook way. And there are lots of nice kits around that offer $significant savings$ for better sound quality. The ultimate solution would be a free in home trial audition of a particular model, but most stores and places stay away from this for obvious reasons.
If one chooses easy street, Circuit City and Best Buy OEM speakers can offer amazing or dreadful sound. The main issue is having a place where one can objectively compare the performance of many brands and price ranges of speakers.
The truth is that there are more amazing speaker systems in existence today than decades ago. We find names such as Mordaunt-Short, Induction Dynamics, Acoustic Energy, TAD, Paradigm, PSB, Buggtussel, Bob Carver's amazing Sunfire Sub-Woofer, B&W, KHT, Dynaudio, KEF, HSU Research, KAVD, ELAC, Totem, Montana, Snell, and ProAC, etc..
After so many years in this hobby, I have concluded that you should buy the best you can afford and upgrade your electronics over the years around a solid pair of speakers. It pays to get the best speakers first. This way you can better appreciate the differences in upgrading electronics.
If you are a Solid State advocate, there are lots of speaker models to choose from, nevertheless a home audition remains the only true way to tell if the speaker system is what you really want and like. Medium to low power tube amps on the other hand do not easily mate well with 'almost all' of the speakers we find in major audio chain stores. I find that for tube amps, one must strive to purchase high efficiency speakers in the +96 dB SPL or higher and spend a bit more money for the best results. Also look for benign impedance characteristics. Efficiency alone is not the benchmark indicator of tube friendliness. Today there are dozens of 'Tube friendly' speakers out there, but generally they are not inexpensive, especially for Full-Range types.
As the art of customer-speaker matching is really subjective, the goal should always be to answer the following question:
a. Can I live with these speakers for the next 7-10 years?
b. Do I have low powered tube or high powered solid state electronics?
c. Do I do Home-Theater?
Depending on the responses, it's better to purchase the best stereo pair to begin. Or a complete-matched set of home theater speakers. Its' best to buy a matching sub-woofer, fronts, rears, and center so that they work together as a team. I know from experience that potpourri home theater speaker setups are frustrating to fine tune.
Home Theater and experimentation with 'disparate' speaker combinations often creates altered tonal balance, and a sound more like a 'Sangria' instead of a 'Single Malt.' My recommendation for Home Theater is to buy the complete matched set of speakers from one vendor. I personally have never used a Home Theater setup so my personal experience with placement, balancing, levels and issues is nil from direct use but I hear lots of friends setups. Frankly the best are the ones that are a complete single vendor set.
Yet if one avails of enough separate speakers to attempt a Dolby 5.1 or ACS setup, make sure that the levels and tone controls are correctly set according to a good Home Theater setup guide. The honest truth is that 90% of existing home theater installations I have seen, do not follow any of the recommended speaker layouts and thusly never can achieve the full benefits of surround sound. The speakers end-up with an ad-hoc placement driven by furniture layout and aesthetics, not sound.
Here's an interesting link to a site that illustrates a method for adjusting the geometry of Surround Sound speakers. I cannot offer Home Theater advice at this time. Yet I understand that Home Theater setups benefit from complete speaker solutions instead of a mix and match approach.
- To DIY or not to DIY:
1. Most under $1000 speakers are built at a substantial $markup$, amounting to nothing more than mediocre parts that look nice together. Most 'mass market' models have been 'optimized' by Engineers and bean counters to sound acceptable by extensive 'anechoic' and computer systems optimization. That is, testing and optimizing designs to account for the poor quality of cheap drivers and crossover components along with particle board veneered cabinets that eventually fall apart in humid weather. Still there has emerged a new breed of loudspeaker companies that offer products worth every penny, even if the markup is still 100%. The scene is better today than 20 years ago in the under $1000 dollar range, even if they are small monitors.
2. Nothing in a loudspeaker system is more important that the quality of the construction, parts used and the attention to the design criteria for Box Volume, mathematical modeling, optimization and the crossover design.
3. Today's modern materials for the actual speaker driver elements truly exceed anything built 30 years ago. All kinds of modern Woofers, Midranges and Tweeters are available to home-brewer's and offer incredible clarity and musicality at great prices. True....... there are classic Altec, Bozak, Dynaco and JBL's that can really sing. But these tend to be old and extreme speakers for an few that may have aged past their prime. Some even weigh too much for a typical vehicle, so get an F150 pickup truck for the larger Voice of the Theater Altecs!
4. Four or five digit price tags usually consist of 50% parts and a 200% markup. The four digit club can offer better than average performance and amazing sound. The +5 digit team usually sells outstanding sound, but one is paying heavily for this. And 90% of these 85 to 90 dB SPL designs require Kilo-Buck Solid State amplifiers with remarkable damping factors to control the low end. Case in point the Utopia Series, especially the Grande Utopia. If you have the bucks, go right ahead and invite me over, I'll bring the Moet Chandon and ice. But... again, this represents 5% of the audio market. Why should the other 95% be made to feel inferior. This represents, in in my opinion, the upper end of the market. Here the State of the art has exceeded the state of the need. I just may have to second mortgage my house for a set of Grande Utopia's. Or take a short cut with the Zu Cable Definitions.
5. For Bass and LF response, a minimum 10" woofer in a must, preferably 12" or 15". It's about the laws of physics. Some claim that 6" drivers can offer amazingly good Bass, may God bless them all at their -3dB 50 Hz HPF pole.
6. A good music room should have a minimum volume of 1500 cubic feet. Anything less and it has been established through extensive acoustical studies that the resulting sound will contain un-correctable room modes and colorations. In effect, less than 1500 cubic feet means an out-of-balance LF audio presentation, but it still may sound good while not being optimal. Some things we must accept... limitations and all. Or call an architect to re-model your house :-).
Any given listening area will interact and play a critical role towards the sound quality of any given Stereo or Multi-Channel system installation. Added to this there are many room treatments marketed that can significantly improve the sound quality in less than optimal setups when properly installed an tested. Michael Green is one expert in this area, and so are many other companies that offer room sound treatment products.
Speaker, equipment setup and selection gets you 1/2 of the way there, but a good Music Room and a proper equipment setup is no substitute for spending obnoxious money on equipment. Things such as isolation from external vibrations, tweaks on all components (Mpingo disks, Sorbothane Feet, etc.) plus fancy cables all help.
- A Two-Way Acoustic Suspension 70 Watt Speaker Project:
There are people that claim no home brew speaker can compete with a professionally built system. Most of these people probably have lots of money to spend. In a general sense, they are fundamentally correct. Most home-brew loudspeakers cannot equal properly designed OEM models at the Engineering and Specifications level.
But.... truthfully, this is about music, not a 1 KHz sine wave. Once you add-up the amount of money it takes to build a great pair of loudspeakers, especially if following a cook-book set of plans and part list, one would be really challenged to buy a manufactured set at the same price and sound quality level.
I believe that in order to enjoy a really superb pair of speakers, an investment of approximately $800 USD gets you right there. This is about all that is needed for audio nirvana, and some woodworking skills too.
This estimated price includes the wood, screws, glue, drivers, damping material, varnish and crossover components. Tool costs are extra here. if you don't own a circular and saber saw with a set of clamps, forget it or start to consider a wood shop for your home.
Sample DIY Speaker Parts List:
- Qty (1) 12' x 12" x 3/4" American Red Oak plank (Lowes)= $110.00
- Qty (2) 6' x 12" x 5/8" MDF Boards (Lowes)= $ 14.50
- Qty (2) 1"x2"x10' Pine Boards for internal bracing and framing (Lowes)= $ 8.50
- Qty (2) 266-090 Audax Dome TW025A1 1" Dome Tweeter (Parts Express)= $ 61.90
- Qty (2) 296-085 Audax AM210Z2 8" Shielded 'Aeroge'l Woofer (Parts Express)= $ 231.00
- Qty (2) 260-317 Acousta Stuff 1 Lb= $ 19.00
- Qty (1) Shop costs for cutting wood: $ 40.00
- Qty (lot) Miscellaneous materials: Wood sealer, Sand paper, Stain, Varnish: $ 30.00
- Qty (1) Radio Shack Book - Building Loudspeaker Systems: $5.00
- Qty (2) Alpha Core Copper Inductor 0.05 mH/0.031 DCR $ 13.44
- Qty (2) Alpha Core Copper Inductor 1.2 mH/0.343 DCR $ 26.98
- Qty (2) Solen Fast Caps 3.0 uF/400V $3.90
- Qty (2) Solen Fast Caps 4.0 uF/400V $4.40
- Qty (2) Solen Fast Caps 15 uF/400V $ 9.90
- Qty (2) Madisound Air Core Inductor 0.5 mH SB / 0.44 DCR $ 5.30
- Wirewound Sand Cast Resistor 3 Ohms/15W $0.80
- Wirewound Sand Cast Resistor 3.5 Ohms/15W $0.80
- Wirewound Sand Cast resistor 10 Ohms/25 Watts $1.20
- PC Board or Epoxy Blank for Crossovers $ 10.00
$596.62 + Love and Hard Work to put these together..............
Add another $300 Dollars for quality tools if you don't already own Clamps, Electric Tools such as Sanders, Circular Saw, etc.
This same speaker, if sold by a Hi-End company, would retail for about $ 3500.00+ USD the pair.
Get the speaker markup picture? You can do much better by spending on kits from Madisound or Meniscus and save some money. But if you aren't handy and crafty, shop around for the best speakers you can afford.
The following companies are excellent for drivers and speaker parts and I recommend that you surf them to get ideas about how to make your own special Loudspeakers!:
Here is the LEAP analysis from Madisound for your enjoyment. I encourage you to design and build your own dream system. It's all a matter of applying some technical know-how from speaker building books and buying the best drivers you can afford. Then you have a LEAP design made and VOILA!
Contrary to popular belief, one can home-brew speakers and crossover networks that can come close to performing like computer optimized speakers, not equal or better, but a $1500 savings close.
We are human, and as such tolerate minuscule differences with ease that most nutty Hi-Fi freaks claim can:
- 'collapse the soundstage'
- 'grossly affect the imaging'
- 'Affect the pace'
- 'Alter the midrange bloom'
No doubt that one can notice BIG differences in sound quality, I know I do! And this is just what one will hear when comparing a $1000.00 USD pair of 'over-priced' Mini-monitors whose cabinets are the size of a shoe box, to a lovingly built 2 Way system with top quality drivers that will sound and perform very well indeed. Maybe not for a perfectionist speaker reviewer with waterfall plots and a better ear than us regular people. But good enough as they say....
I can now picture Mr. Klipsch with his hidden lapel pin that said 'Bull-$hit' whenever he heard the opinions of 'experts' at many an Audio trade show past.
These solid cabinet, two way speakers were built by me back in 1995 when living in Lynchburg, VA. They are constructed from a core of 5/8" MDF, braced internally by 1x2 pine with over 80+ Wood Screws. They are internally coated with 'Black Vehicle Under Coating' and finished with a Red American Oak panel which cost me $110 USD for a 12 foot piece or about 9 dollars a board-foot.
These speakers have an incredibly simple non-optimal crossover design, whose calculations I derived from the Radio Shack Speaker book. I opted to cut-over the crossovers at around 2500 Hz, but it's more like 2550 Hz according to the final calculations. This bi-sects the frequency responses of both drivers. The Woofer is up to 3000 Hz and the Tweeter goes down to 2000 Hz, therefore the crossover is at 2500 Hz. The design is based on Second Order Linkwitz-Riley 12 dB per octave. In addition I added a Zobel Network across the woofer to smooth out the response.
The new crossover is a LEAP based one, see above LEAP and updated parts list. The original crossover used uses 3.9 uF Solen caps and 1 mH Perfect-Lay air core inductors. The Zobel Network across the woofer terminals consists of one 10 uF/250Volt DC and an 8 Ohm non-inductive resistor in series. This reduces the impedance rise of the Woofer voice coil, smoothing out the LF response. The tweeter is wired 180 deg out-of-phase as per the standard 12 dB per octave Second Order crossover design.
As the crossover was only a home-brew approximation, I now have a LEAP designed version and just ordered the parts today 3/30/05. The performance of the new crossover should improve significantly with a LEAP computer modeled design than what I used before.
Originally I had the tweeters attenuated by 2 dB, but I now just run them direct. When the tweeters finally broke-in, the sound really smoothed out and any 'peakiness' they has simply faded away. Removing the tweeter attenuation network opened up the sound. I have no grilles, as these affect the sound in a way that I prefer their absence altogether.
The French Audax drivers are simply superb. I cannot have more praise for this company that is among the few manufacturers of truly state of the art driver technology.
These monitors have outstanding clarity, good bass extension and a presence that few speakers in the $500 dollar range can equal. I did spend over $260 USD a piece for a pair of JBL LX500 speakers. They compare favorably to my monitors, but are a three way design and lose some of the sonic benefits of two way designs. My home brews make better music, not better sine waves.
One thing that I must mention, when I moved from Lynchburg, VA to San Juan, PR the speakers were affected by the high tropical humidity in my country. Hence the front and rear Oak pieces expanded and actually became un-glued from the main body at two places.
My best friend is also a Luthier and intimately familiar with wood. He builds and repairs Guitars and Puerto Rican cuatros, tiples and bordonuas so he re-worked the cabinets for me. I can say that they are still in need of one more round of shaping and a final varnish to seal the wood pores. My buddy is waiting for me to take them back for this. At the moment they are stable.
I do plan to build another pair down the road with native Puerto Rican wood (not veneers.) My philosophy for speaker construction is that the cabinet must have lots of mass and be resonant free. I mean MASS. Without the drivers installed, my speakers weigh in each at over 55 lbs. each. This is critical to the sound of any speaker and mostly today a good measure of it's build quality.
If you plan to build these I would more than gladly send you my sketches and plans for this model. I can only guarantee the sound if you buy the same drivers I used that are still available from Parts Express. I will put together a detailed parts list and crossover schematic and I will add it to this page for free, plus a wood cutting layout.
The cabinets measure = 17-1/2" Tall x 12-5/8" Deep x 11-5/8" Wide. My original plans that included all cutting and measurement data was lost in a Hurricane George flood. I will attempt to re-create this design as faithfully as possible, including the resulting internal Box Volume calculations.
As I do plan to order a LEAP crossover design from Madisound, at the moment the plan is to convert the existing crossover to a LEAP Butterworth 3rd order 2-way all-pass and constant-power crossover. For this project the best parts possible will be ordered and a complete project should emerge.
Once I receive the LEAP crossover design from Madisound, I can proceed to optimize the construction of the replacement crossover and have my friend re-finish the cabinets with good dose of elbow grease and varnish.
I ordered a LEAP design for the crossover. Once this arrives I believe that a computer modeled circuit should improve the sound significantly for the better. More after it's installed.
April 2005 update:
Most of the parts for the new crossover have arrived, except for the Alpha-Core inductors. As soon as these get here It should take me about 2-3 hours on the bench to produce two quality crossovers. Then the installation should be a breeze into the cabinets.
LEAP Crossovers installed 5/1/05!
I have to say that the sound of these speakers has improved so much that they now present a credible image and a very deep and harmonically rich soundstage. The LEAP crossover service from Madisound is nothing short of a technical marvel. I opted to the full design that includes a notch filter for the upper treble region.
As words cannot truly describe these speakers, what I can say is that the next thing I will do is to include some specifications on the cabinet and a how-to go about building them.
I am now looking forward to more of these and less to the rest of my speaker collection.
The speakers are almost 100%. Yesterday I re-installed the Woofer with some Tee-Nuts. This allowed for a top notch seal and mechanical fit to the cabinet. The Bass response was immediately better with much cleaner upper bass and lower mid's. All that is left is to install another 1lb. of Acousta-Stuff across the two cabinets. The cabinets are now 50% stuffed but need more stuffing. I placed an order with Madisound Speaker Components and it should get here sometime late next week. I am overall very satisfied with the design and the results. I sure hope that my friend can finish the cabinets with one good last coat of Polyurethane. I will take a photo of the new Crossover when I re-stuff the boxes. Now I am intent of justifying the Zu Druid Speakers as my next purchase, if I have extra cash left-over by the end of the year. Despite my love affair with Home Brew speakers, I still believe that the professionals can do better than the amateurs with the test equipment and R&D dollars at their disposal.
Purchased in 1977 at the Post Exchange - Sabana Seca US Naval Communications Station, PR.
Model 501 Series II 60 Watt RMS; 4 Ohm Nominal Impedance (more like 3.5 Ohms)
Voila, my first pair of 'High-School' speakers. These speakers have rocked the foundation of at least 60+ different parties from 1976 to 1991. In 2003 I re-built them as these 501's went dormant after a severe case of 'foam-rot' and a total meltdown with Rick Wakeman's solo of Yessongs in 1988 with a 105 watt RMS Onkyo Integrated amp. The woofers were initially Radio Shack 10" replacements and most of the HF drivers were blown that night. The Radio Shack woofers survived and were given to my friends.
I actually had 'tossed' the original 501 woofers (arrrgghhhh) back in '82 due my ignorance about how simple it is to replace the foam on rotted surrounds. The 501's spent over 10 years at my friends house as stands for his Linn Helix speakers and 3 years as a Rat hotel in my backyard shed.
Managing to source the original Bose 8 Ohm Mid-Tweeters and 6 Ohm 10" Woofers from an Ebay bid, I also obtained some earlier Series I original fabric grilles from a parted 501 model, I the restored them and installed them.
The original Series I and II crossovers have a 'car' light bulb series limiter/attenuator in the crossover, strange but true, this was also replaced from a Western Auto part. If you crank up the speakers the lamp will light on peaks!
I am now, once again, rocking the house down Bose Style. Yet I recall having read on a forum that one person said
"No highs, no lows, must be Bose"
These speakers are party speakers. They play loud and good at that.
Bose 501 speakers are not the ultimate in detail, but they have a sentimental value difficult to describe and work well to play music a higher volume levels for most parties.
JBL LX-500 3 Way Bass Reflex
Purchased new, 1993, Lynchburg, VA Circuit City
Next to the late Ericsson GE plant located at #1 Mountain View Road and Liberty University
Rated at 150 Watt RMS into 8 Ohms (I would not put 150 watts into these)
These JBL speakers are just another 'average' sounding commercial Circuit City purchased 3 way design from JBL.
The main drawback about new JBL products is that their replacement parts are very, very expensive and often require a core trade-in of the old part before they will even sell you a replacement driver part.
Implementing a Titanium Dome Tweeter, these speakers can play nicely and seem to pair well with my higher powered tube amps in the +35 Watts RMS per channel or more range. Any less power and the sound runs out of gas. Yet they are boxy in their bass sound.
These speakers have seen their share of accidents. I blew both tweeters to the tune of $125 dollars for both, the woofer foam rotted at about the 6 year mark.
I use the JBL's whenever I want to hear some 80's, 70's, Disco, Pop, Jazz, Rock or Medium scale music. I spent $545.00 USD for the pair and to this date I believe that I over spent by about $200 dollars. The cabinet build quality is good, internally there was evidence of cheap glue-gun mounting of the Port tube and the crossover unit to the inner walls. The speaker connections are the 'ultra-cheapo' push-in type.
After upgrading these flimsy parts, and sealing the Bass Port with silicone, a much better bass and sonic presentation emerged. For the money I would look elsewhere. But if you can find a pair for under 100 dollars then go for it. The tweeters don't take kindly to Solid State harmonic clipping distortion so watch out as they are $expensive$ to replace.
My suspicion is that these speakers have a 'tough' impedance situation, but I may be wrong. A plot of impedance and phase angle would reveal if these speakers are tube friendly, I suspect not. The bass is lumpy and the sound does not remain coherent at different volume levels. Honestly, these JBL speakers sound better when played moderate to loud. On softer music the presentation becomes disengaged and vague, especially on Piano and Voices. Once again I would classify these as 'boxy' sounding. You need to crank them-up to get the correct sound. The LX-500's play very poorly at low levels.
MCS JC Penney 3 way Hand-me-down speakers.
12" Woofer, 2 x 2.5" Orange Fabric Dome Mids, 1 Orange Fabric Dome Tweeter
150 Watts RMS rated into 8 Ohms
Nothing compares to the sound of a cheap pair of high powered speakers. I use these speakers whenever music and large amounts of alcoholic drinks are to be consumed. I can't say that these are Hi-Fi. I have blown the Voice Coils of the original woofers, blew-out one of the tweeters and now one of the midrange drivers is making a buzzing sound. But, they have served us well when impromptu DJ parties are created during holiday's. We can make loud noises, crank up as much Bass and Treble as the people can handle and with special effects CD's, upset the dogs in the neighborhood . When will we use them again??? Who knows. But they are ready for Rapid Deployment!
GIVEN AWAY TO MY BROTHER IN LAW, MAY THE MUSIC LIVE FOREVER!
- Pilot Radio Corporation PSV-2: 3 Way: 16 Ohms: built in USA
I purchased these unique 3WAY 16 Ohm Alnico speakers on an Ebay transaction from a seller in South Florida. One woofer buzzes at 330 to 500 Hz. I had taken the driver out and tested it with a signal generator, sure enough, it's got a Voice Coil problem or some other anomaly that makes pianos sound gritty.
Here are some photos of this vintage-americana speaker. I can say that Alnico and Tubes love each other. Hopefully I can get both woofers professionally re-coned as these speakers sound pretty darn good on Classical and Opera. They also make some nice Jazz music and may also be used as a movie prop in a 60's era film.
I 'attempted' to replace the woofers with some new Jensen Alnico 16 Ohm Guitar speakers and they sounded dreadful. I believe that they need to seal better against the front panel as the midrange driver is concentrically suspended by 4 brackets that separate the paper gasket and cause air leakage. Apart from having that 'real retro-look', the little I heard from them I liked allot! Stay tuned for further action!
Hi there.... after a long dormancy period I un-boxed the Pilot woofers for a closer inspection. The fault is something I personally have not yet seen. I think that the buzzing woofer is under spider/surround tension. What this means is that when the woofer was originally assembled, the geometry of cone was such that when the spider was glued to the rear of the basket, the accordion surround ended-up under tension, being pulled by the spider. This resulted in a cone that was not free to go into free pistonic motion and the spider buzzes at certain frequencies that are in the range of 350 to 450 Hz. This causes the spider and cone to 'resonate.' I have sent off for a re-cone quote for both woofers. This is a job that I best leave to the pro's. I can safely re-foam speakers. But to re-cone is a completely new area for me, and such special 16 Ohm drivers are best left to the pros!
The Jensen Alnico drivers have finally broken-in. The Alnico sound is classic, with a hint of nostalgia. These speakers work very well now, but require warm-up to sound their best. One hour of Rammstein or Dream Theater and they are good to go with some Brahms!
It's been over a year and these guys are getting ready for some OTL action. My buddy owns a pair of souped-up Atmasphere M60 MK3 Monoblocks. With 16 Ohm speakers, I can only wonder how our musical experience will evolve. Stay tuned for the shootout at the OTL corral!
Latest Speaker Happenings at The Music Room:
Living Voice Audiophile Speakers
Last night I heard a pair of floor standing speakers that sounded as good as anything I have ever heard. These speakers are made by a U.K. firm called "Living Voice". Music was reproduced with a sense of ease and coherency that baffled me. The small low-mid drivers are able to capture the essence of the sound in ways which I do not truly comprehend.
Fit and finish were amazing on this particular pair, despite the shipping damage to one cabinet where the dust cap was pushed-in and the cabinet was scuffed.
The electronics implemented were:
- Atmasphere MP-1 Preamplifier
- Cary Audio 300SE Mono-Blocks (WE 300B and RCA Red Base Input Tubes)
- Njoe Tjoeb CD Player with 192KHz Swiss up-sampler and all factory upgrades.
-Nordost Speaker Cables and other goodies
These speakers are very good value for the money, as compared to other competitive products. The veneer on these speakers is book matched and is very indicative of excellent workmanship. These speakers are also pair-matched so if one has to to back to the factory, they both have to go.
As amazing as these speakers sound, it may be many month's before I can have a budget for such a marvelous sounding pair of speakers.
I do find it relatively obvious, when choosing the best speakers possible to venture beyond brand names and the common every day products we see. But, not often are we able to audition these special products.
Thanks to Milton and Frankie for giving me the chance to audition these wonderfully balanced products, I am impressed by these loudspeakers and how coherent a presentation they provide.
I can, with the little I heard recommend these speakers to any solid state lover and tube push-pull advocate. SE amps should be of the higher powered types. The 6 Ohm nominal impedance does have some tube friendly drawbacks, yet It did not seem to bother the Cary amps 8 Ohm taps.
Bose 901 Series IV
Yesterday I picked-up a NOS pair of Bose 901 Series IV speakers at my friends house. The pair is in OK physical shape and were surely ready for some testing. Never would I have imagined pairing up a pair of these special speakers with tube amplification. Nevertheless, I turned them on with my Aurora amplifier and PAS-4 Preamp EQ loop and amazingly.... the 901's played very well. But.... they have the dreaded foam rot and are in need of a major overhaul that is not going to be cheap when you factor the time and money to be invested.
After some expensive repair, I managed to coax them back to life. Here is my most recent experience with the Bose 901 speakers. Truly, these speakers are NOT Hi End, they are designed for the laymen who want to really hear sonic fireworks and distortions of the actual recordings. The user has three options with the equalizer unit. There is a Bass cut switch, also there are Midrange and Treble controls that allow the user to make them sizzle or whisper.
This is my latest romp with the 901's. I want to recommend these speakers, especially for people who listen to Home Theater in Dolby 2.0 and don't have the space for a Multi-Channel system. Also Bose 901's are best mated with 100 Watts amplifier power. They work equally well with Solid State or Tubes. The minimum tube amp power I suggest is 60 watts. Solid State can be 40 watts. But these speakers shine with more than 100 watts power.
BOSE 901 SERIES IV..... LIVE AND LOUD !
On to the 901's and Live DVD Concerts
I spent the last weekend enjoying some Live Concert DVD's playing through the Bose 901's.
DVD's listened to:
David Gilmour - Live at the Royal Albert Hall
Foreigner - Live in Germany
Alan Parsons - Live in Madrid
Jefferson Airplane - Fly Jefferson Airplane
Fourplay - An Evening with Fourplay
Andreas Wollenweider - VOX
Vangelis - Mythodea
Rainbow - Live in Munich 1977
RUSH - Snakes and Arrows LIVE
Aikido Octal Preamp 6SN7 @ 300 VDC Regulated
Oppo DVD Player
Transcendent Balanced Power ( sources only )
KT88 Fixed Bias 60W/ch Monoblock Amplifiers
Bose 901 Series IV, PC6 Stands & Matching Equalizer
Monster Cable XP
Vampire & Nordost Spellbinder Interconnects
Great Live performances within the context of Bose sound
The 60 Watts of KT88 power per channel did more for Live DVD's than any other prior setup I had used.
Especially in my 1450 cubic foot music room, the 901's filled the air with plenty of excitement.
Of course 901's are not Hi End sound, but how many Live Concert events are recorded and relevant in this context ?
The way that Bose 901 speakers deliver and convey Live Music is satisfying, with punch and energy.
In essence, judging the sound of Bose 901 or any Bose product from the Hi-End perspective is probably misleading.
I will state that Bose sound is Bose sound, like Klipsch or Maggies.
Bose seems to have strong Public Address audio roots.
This is obvious from today's product lines for roving musicians, weatherproof speakers and commercial audio.
The Bose sound is based on a Direct/Reflected concept and as such, an iconoclast in the Hi-End speaker world.
Also Dr. Amar Bose created the concept of Acoustical Masses.
I have a strong hunch that Dr. Bose probably used a Plant Coefficient Matrix and Control Theory.
Bose has always managed to sell their products as "Better sound through technology"
And Bose manages to do this at a decent price point with the Bose 901's. I cannot say the same for the 123 Systems, etc.
Despite pressboard cabinets and other low cost materials, the 901's pack lot's of technology into two small cabinets.
Bose 901 speakers require active equalization and include a matched audio equalizer unit.
This technique is viewed as another source of "distortion" for the purists.
Active speaker equalization is rare in a product sense to buy the speaker and equalizer together as a matched set.
Bose 901' s pass on the mish-mash of live stage music in a similar way as we hear it in the live environment as sonic mashed potatoes
Live music, unless it's a small quartet, trio, or intimate Jazz Club recorded with carefully placed microphones arrives to our ears pretty much mixed-up with a mix of delayed reflected sound and faster direct sound.
Maybe in a open air arena we can hear the Bass on the left and the Bongos on the right, maybe there's some spatial info.
Bose 901's don't do studio, vocal and instrumental recorded material well, but for most people this simply is not relevant.
Good LP's lose spatial definition and high quality recordings can sound a bit congested.
What the Bose 901's do well is to "to spray music" with plenty of low end punch.
They also have a lack of high end extension that is probably due to the lack of a true HF radiator.
But 90% of Music is not in the tweeter range so relevance to the total is not that big of a factor for the average person.
The 901's Bass has snap, is very fast and deep enough to enjoy Jurassic Park.
Amazing how the Bose 901's can rattle the windows while my Zu Druid speakers struggle to convey the same message.
Heck it may be distorted but it sure appeals to the normal person.
I have impressed very few laymen with my Hi-End sound. But put on the Bose and they smile.
The Bass performance from the 901's is fast and nimble, commanding and almost specializing in Live Musical Reproduction.
One listen to studio recordings and my ears tell me the Bose 901's are not delivering the information well.
In fact, recordings with ambient and spatial cues that require careful driver phasing, the 901's are lacking.
AC/DC Live at Donnington, Supertramp Live, RUSH Snakes and Arrows or even a large scale symphony/big band.
Bose 901's deliver that "On-Stage" message very well for a decent price point.
Bose 901's have most of the Bass I will need without the added expense of a dedicated Subwoofer.
My music room is 1456 cubic feet in volume and the 901's fill this space very nicely.
I actually removed the area rug to achieve a hotter presentation that went well with Live DVD's and CD's.
My back wall is covered with Sonex so this helps in the overall presentation.
So in a nutshell and without too many extra words, Bose speakers are the layman's home version of a PA system.
They deliver musical thrills like a small roller coaster ride but have nothing to do with the way Audio-holics prefer music served.
In fact the 901's are an acquired beer budget taste, not a refined Cognac or Merlot.
So if you want to make loud music, have a 2 channel home theater and small speaker requirement
I would try out a pair of Bose 901's for sure, especially if you have a Solid State Receiver.
You need at least 60 watts per channel, 100 watts ideal and 250 Watts the best.
The idea is not to melt the 901's, it's about headroom and transient performance.
I wonder how 901's would work with a NAD M2 or a Spectron Musician III, ummmmm ??
Bose 901's don't:
Image or recreate acoustic spaces
Zero pin-point sound-staging
Absent "you are in the studio" feeling
No reproduction of spatial cues
Flat resolution of micro dynamics
Bose 901's do:
Make nice Large Scale Pipe Organs sound real
Re-create the thrill of most Live recorded performances, especially loud one's
Make most poorly recorded material palatable
Eliminate 'sweet spot' listening
Solve speaker limitations with active equalization
Bose 901 speakers are idiosyncratic
Not hi-end in sound or performance
Are a classic design.
Have stood the test of time.
Still quite affordable new in today's $dollars$
I would classify Bose 901 speakers as "Party Animals", but Stereophile doesn't have such a category yet.
Retro, reasonable and powerful... at least Bose 901's rock !!
My Bose roots go way back to the 70's so read on.
My experience with Bose sound goes way back to 1977 when my buddy bought a pair of Model 301's. At the same time I traded for a pair of Post Xchange (Sabana Seca Naval Station) purchased Model 501's Series II's, I still have them !!!!
In my opinion, Bose speakers work well for the masses, yet audio Hi-Fi nuts find serious sonic flaws in ALL Bose products. As you can see from my appreciation above, this still seems to be the case. Bose sells "Solutions" not "Products" and even their line of speakers are based around this concept.
I prefer to ignore angry people when they insult the Bose sound. To judge Bose's virtues and limitations is to question a design philosophy that apparently (the proof is in the sales) has worked very well for Dr. Amar Bose and company. This company over the years, has had a philosophy rewards it's customers on almost a constant basis with state of the art support and trade-in services. The Bose return policy is a model in itself. There are simply no caveats of fine print, if you don't like the product, you can return for a refund within the initial 90 day warranty period or trade-in for a newer product .
Me.... well my 501 speaker grilles went south in '79 when a wine and candlelight music session saw candle wax melt all down the side of one 501 cabinet. A hand written letter with this story about the candle amused the folks at Bose enough to mail to me, years after the warranty expired, a brand new pair of Bose 501 grilles, NQA (No-Questions-Asked.)
After 7 hours of CD's and some KILLER DVD's I find that the 901 Series IV speakers:
1) Play well at low and high volume levels so they at least work with some kind of flexibility.
2) Achieve a very satisfying and fast lower octave presentation, the bass in never bloated or lumpy, yet lacks the ultimate in detail.
3) Project a diffuse upper frequency pattern that works best with live concert music and has zero imaging capability, the music seems to come from everywhere.
4) Compact and easy to own, the 901's can safely handle LOTS of music power without any early distortion artifacts. Many small drivers working together.
5) Tedious to repair and re-foam unless you have the correct factory kit and oodles of time and patience.
Bose... either you love the brand or vehemently swear that it's nothing more than pressboard, veneer and el-cheapo drivers.
If I took a census on all the audio forums out there, there are more Bose bashing 'un-friendly' posts than those that talk well about these products. Are Bose bashing people suddenly audio experts? I probably think Bose bashing is a trendy thing, not rooted in any serious foundation. Bose hatred in my mind is totally is un-warranted. Unless one has a real problem with a warranty or a non-performing product, hating Bose for the sake of being another angry forum snake is not cool business. Bose fills the needs of the masses. Unfortunately the majority of consumers can give a rat's a$$ about imaging, sound-staging, depth, speaker placement, coloration, or phase/impedance graphs. People just want to push play and receive music no matter how dreadful the bass or how screeching the treble. One look at the midrange performance on most commercial speakers and the writing is on the wall.
In my opinion, Bose products combine technology, particle board, nice veneers and extensive marketing. Their drivers offer quality sound anywhere from about 5 to10 years, maybe 15 in Arizona. After that, Bose speakers foam rot and fall apart quickly in the Tropics. But the good news is that kits are readily available.
Most Bose products are subject to extensive revisions and parts changes, making their repair and restoration very tricky. Once you change out one component with a substitute, some of the Bose sound just fades away. I found this out the hard way when working with my particular Model 501's. The replacement woofers and tweeters from an earlier model series significantly altered the tonal balance of my speakers and it's probably due to the different crossover that is computer matched to a specific driver combination. You change one thing and the sound quality quickly collapses. I do have the original crossovers and they are different from a Series II.
The best way to own Bose speakers is to 'set-it and forget-it'. The direct/reflecting concept limits placement options for most early models, especially the 901 series that require a clear back wall to strut their stuff. 901's are especially demanding in terms of placement as they require a flat rear surface for the reflected sound effect to appear. 901's depend on reflected sound for doing their special thing. Almost all of the 901 drivers face to the rear of the cabinet, hence a clear back and side wall is a must for Bose owners. Bear in mind that the obligatory 901 Bose stands are necessary to make the complete package look elegant and become a functional solution, or you can hang them from the ceiling with small chains for that special Lava Lamp era look.
It is too early on my part to completely judge 901 speakers personally as I have only heard this pair for 7 hours or less. Yet once I get a better idea on how these 901 speakers behave with different sources of amplification, a better understanding will emerge. Thank goodness that my PAS-4 Preamp has an EQ effects loop for the Bose equalizer.
I believe that 901 speakers have not ever seen much in terms of tube amplification, a thing that I found surprising when playing the 901's a lower levels, the sound stays open and coherent. Not having an phase/impedance graph to look at, I may search the Stereophile or Audio Review archives to check for this info.
This gift assures my friend of a ShermanAudio production tube amp, with a special plaque dedicating my design to my High School Soccer Coach, Algebra and Trig mentor, Paul. Thanks for such a wonderful hand-me-down.
The Bose 901's were tested with tube amplification and they sound great. Give them a try with tubes, you won't be disappointed. The amplifier used was my restored Dynaco ST-35. I went from my 100 Watts per channel into 8 Ohms ADCOM Stereo to my 17.5 Watts per channel Dynaco ST-35. The change was nothing short of a complete smooth transition from an edgy, harsh and tight presentation to a smooth, lush and non-fatiguing sound. The cymbals took on a nice sheen while the Bass became much deeper sounding but way less controlled. I plan to experiment more with the 901's as these speakers appear to be tube friendly. With no internal crossover and large voice coils to create large amounts of back EMF, low damping factors don't seem to be as much of an issue with the 901's.
Zu Cable Druid MK4 Loudspeakers finally arrived - Tokyo Frost, amazing sound !
Not until we hear single driver speakers do we become aware of point source truth in sound. Such pure sound can mimic nature and radically change our perception on where the limits or reproduced sound really are. Chirping birds and barking dogs can fool my dear Pug into barking every time, and only when played through my Lowther PM6C drivers.
Well all said and done about single cone drivers, my quest for Tube friendly speakers has led me to Zu Cable. For some audio enthusiasts, tube friendly means high efficiency above all other parameters. For other's, tube friendly means a benign impedance characteristic. For me "Tube Friendly" means a synergistic match between speaker and amplifier.
The Zu Cable Druid's upon my first seconds of auditioning sounded immediately like I imagined a larger Lowther driver would sound. Yet the music came through larger, deeper and fuller than my Lowther speakers, and must I say probably better in many areas, especially the low frequency octaves.
I am one who can only listen to certain recorded music on my very 'nude' and 'revealing' Lowther Minitower System. My Lowther speakers were guilty of showing me that large differenced in the mixdown quality exist in CD's. Some sound dreadful on Lowther's, yet other CD's sound simply awesome. The same goes for LP's, Reels and Cassettes. My Lowther's then became a musical courtroom with lot's of guilty verdicts and many a mediocre CD getting slammed into mediocrity.
The Zu Cable speakers did something similar, yet they took me further along the path towards sonic bliss. They are revealing, but not judgemental, the Lowther's are subjective while the Zu's are objective. Finally I arrived at a place where I did not expect to go so soon. Products like these don't get much press. Yet for all of the people who own tube amps and suffer from constant speakeritis, prepared to be transported to Zu Land.
No doubt that my preference for the Lowther sound with extreme neutrality as driven by my 'baby' Dynaco ST-35 or Kismet 2A3 home brew amp is well known in my 'local' circle of audio nuts. But, idiosyncratic low powered SE topology 300B and 2A3 amps often take me closer to some artists and farther away from others. This all seems to depend on the 'quality' of the recorded material, more than the hardware setup of the equipment.
Enter the Zu Cable Druid MKIV's...
The Zu Cable Druid MKIV's were much less prone to making music sound a certain way as the Lowther's do. Druids are dead neutral and utterly transparent. These speakers seems to get along well with most any tube amp, presenting to them an easy load and a wide frequency range transducer buddy. Yes I had arrived at a place where tubes and speakers were getting along very well. These Zu cable speakers auditioned by me were imported by a local Zu dealer and were just starting their journey towards a 250 Hour break-in period. Was I ever more impressed, finally a no frills tube happy speaker for under $5000 USD!
Not to also mention that connecting to the Cary 300 amps were the top-of-the-line Zu IBIS speaker cables. The complete audition was heard through these Zu cables despite the fact that I had brought along with me some 2 m pairs of QED Anniversary Cables purchased in Slussen - Sweden, just south of Gamla Stan over the bridge joining these historic districts. My only trips were an occasional bathroom break and an ice cold Beck's to soothe my hydration requirements.
Who are Zu Cable? ........ http://www.zucable.com/company.html
To me Zu Cable is a company dedicated to perfecting music reproduction. Zu have been around for several years, yet they are as new to me a month ago as they are today. Hence, I am just discovering what marvelous music sounds like. Zu designs allowed me a passage to the next level, and these are their entry level models. Zu also offers a 4 Ohm, Active Bass Module tower that boasts a textbook perfect impedance and phase plot. If you ever wanted to see what a full range system should technically show, the Zu top of the line speakers are the one's to beat. If the Druids sound great, the Definition speakers have to be the absolute finest. I am hoping for an audition.....
Zu Cable designs, manufactures and offers unique audio products for sonic perfectionists. You can peruse Zu's "mostly-under-construction" web site by following the link below or read about Zu by clicking on the link above.
The Druid Dark MK4, the collage was cut and pasted above from their Web page, (I will post some actual photos soon ) is a very handsome, sturdy and elegant floor standing speaker. It's quite tall, shallow and wide with not a hint of conventionality. The Druids sport special and unusual custom HF and LF drivers, along with a very high quality build and Cardas speaker interface. The Druids are available in ANY custom color you can ask for (extra charge.)
The have been built in Stark Red [http://www.soundstage.com/revequip/zucable_druid.htm], yet they used here a different Audax Soft Dome tweeter on this version. The Druid MKIV's use now a special silver custom tweeter that sounds deep, like a horn driver, still open and airy like a dome. To me the best of both in one unique design.
The Druids Dark MK4's have a spiked base platform with a bottom firing open port, so they must be lifted from the floor for the Bass port to operate. The cabinet design, or should I say the bass tuning, is a unique solution devised by an expert on the subject of designing exhaust systems for motorcycles. This design goal is very "thinking-out-of-the-box." The bass is clean and tight, as if to squeeze more horsepower out of the woofer. More about this unique bass loading technique is discussed on their web site.
Zu Cable calls this type of enclosure loading "The Griewe loading" after the designer who invented the theory behind this exercise in modern physics and Motorcyle optimization.
The Druids sound tonally correct. Vocals and instruments are amazingly portrayed in velvety hues and silent whispers. Mind you, these speakers were not even close to being broken-in yet. The effects of proper break-in are extended frequency response and smoother sound. My friend called me yesterday to invite me again, he said that the sound is better, I can't wait.
I dislike 'boomy' bass. The Druids are the FIRST 10" driver speakers that did not even come close to having Bass Boom issues. While other professional reviews of the Druids state 'a lack of lower octave presentation'; I would say that the Druids are Bass 'optimized.' Any lower, deeper or louder and you are already out of Druid Land and delving into Subwooferness.
The Druids present such a 'revelatory' improvement in bass clarity over my Lowther's and similar single cone speaker systems that the low end fit the mid's and highs like a glove. The bass region is painstaking clear, satisfying my need for quality LF, not quantity boom. The bass was fast, almost too fast allowing the mid's to be sweeter and the highs more extended. I still can't get over the Druids after 1 week and by the way, my Dynaco ST-35 never sounded so sweet! Darnit it was my speakers all along. Now I plan to re-discover my amplifier collection. The Druid's are probably the Stargate to audio heaven, and my tube amps are all awaiting their turn to travel.
The Druid sound overall?
Well... I can say that without any real break-in, these speakers are truly tube heaven wonderful. The Dynaco ST-35 was connected to the Druids at 16 Ohms. The Druid speakers claim not to drop below 7.5 Ohms and exhibit a 12 Ohm Nominal impedance that pretty is flat across the audible sound spectrum. With such a marvelous integration of Woofer and Tweeter, the Druids represent the best in simplicity and phase coherence. Believe me, it's not simple to integrate a woofer and tweeter together to work as one, on the Druids I did not get a feeling of 'cross-overness.'
Would I buy a pair of Druids? YES!, even if my wife screams bloody murder. I own too many speakers already, so I may even have to consider selling off part or all of my speaker collection to buy a pair of Zu Cable Druid's, but I would like to hear the Definition before I purchase. Something tells me to audition them along with other speakers to get the complete picture. I read about Coincident Technology Victory and Total Victory speakers and remain curious before I make a final decision. Only time and space will tell if this will be the case or whether I go for the Druid's.
Here again is the philosophy of buying the 'BEST' speakers one can afford. If you have the money, don't settle for less. Always lay down the green on good speakers. Yes DIY is nice, but I can never pretend to achieve sonic perfection from my garage. Speaker manufacturers avail of test equipment I lack, and such investments are prohibitive at best. With speakers, stick to the Pro's. Furthermore DIY amps can then have a clear voice and the ability to show if further tweaks are due.
The Druid speakers did everything I wanted very well, up to now. I was transported to vocals that were sonically correct, Jean Michel Jarre AERO was crisp and extended right there in the room with us. Stanley Clarke 'plucking' before our very ears, the strings on his acoustic bass, courtesy of the "Rite of Strings" CD.
The delicately-thunderous coherency of the music these Druids created makes me want to stick around my friends house much longer than a 9:30 pm leaving time. Amazingly after +3 hours of musical heaven, the curtains were drawn, my Dynaco ST-35 was packed and I was not nearly as happy as when I arrived, a sad departure, I need another Druid fix.
I hope to listen to the Druids again, and just maybe own a pair before the summer starts. My 'planned' Plasma Monitor purchase may just take a back seat to the Druid-MK4's. Darn it, another delay with the Plasma.... Yet I am still a music lover at heart, as for me DVD's and VHS are still in secondary mode. I feel that the visuals somehow interfere with my ability to focus on the music. I can hear CD's, Reels and LP's for hours. Yet, after two music/concert DVD's I somehow feel visually exhausted and ready for a plain ole' Cassette, CD, Reel or LP, light's out and that dreamy bliss envelopes me.
Music first, video second and strange opinions third............
The Druids called me last night, and I responded. The lineup was a Hi-Fi Winkel/Upscale Audio Njoe Tjoeb 4000 fully loaded with a 192 KHz Swiss Upsampler, the special power cord, Tjoeb Shoes, tested Russian Rocket Logo 6922's and one souped-up pair of Cary Audo 300B Monoblocks using CV378 rectifiers and WE 300B's, topped off with an Atmasphere MP-1 preamp, whipped cream and a cherry.
In short ... the works. With the Druids, the Cary SE 300's and the Dynaco ST-35 both created a different yet believable sound stage driven by the Atmasphere MP-1, but as these are not balanced input components, we may have even better luck with some OTL amps.
This is where we were and we hope to be back again soon. More CD's, Cold Beck's and time to enjoy.
To the people at Zu Cable, job well done. Zu Cable truly understand the 'art' of speaker design and the 'needs' of tube lovers all in one statement product. With such an amazing product line, Zu Cable is one of the most innovative and promising audio companies today.
Now that 'low damping factors' are a thing of the past, I surely hope to write more about Zu products. Eventually I may own a pair and play around with sources, amps and cables. I ca then expand on this review and list the CD's, LP's and Reels used to enjoy a bit of music and happiness all in one.
Last night I had another chance to audition the Zu Druids. The Druids performed very well and I can highly recommend these speakers for music lovers. Not as good with Rock and Roll as speakers that have full range capability, the Druids provide clarity, realism and that tube synergy only a 2A3 Single Ended amplifier can provide.
These speakers receive a good buy rating from our listener group. If you are in the need for a pair of speakers that do almost everything a Lowther can do but better in most area's, the Druids are the place to start, and probably end.
The price is quite good considering typical loudspeaker markups and profit margins. With the next level around 10KUSD, I would call the under 3KUSD Druids money well spent for 2-channel music enjoyment at home. As soon as I have my very own Druid's, I will post photos and some measurements for your enjoyment.
I am saving-up for a pair of Druid MK4 Tokyo Frost with a 2m pair of IBIS cables. I hope to have these speakers sometime in April this year. Once I acquire these speakers, I plan to sell most of my collection so stay tuned....... If you are interested in any of the aforementioned speakers just shoot me a mail.
Finally the Druids were ordered along with a 2m pair of Ibis Speaker cables. These should arrive by the end of May and my expectations remain as high as the last day that I heard them at my friends house. Apart from a lengthy break-in period, all of my Tube amps should benefit from the benign impedance of these wonderfully detailed speakers. Actual Photos and impressions will be posted here.
The DRUID MKIV speakers arrived yesterday. Initially the speakers were connected to my Aurora amp, but later on they went all out with my Monoblocks.
I cannot say enough about these speakers. They sounded amazing right out of the box, literally speaking. We all suspect that this Druid is an upgraded model, or that the Tokyo Frost finish actually makes the speaker perform better. Anyway, wow, wow and wow. I just went from a straight Middle-Class neighborhood to Upper Class. You can see them in my Music Room main page at the bottom.
We also tested them with a short pair of Cardas Golden Reference speaker cable. This alone was also quite a revelation. Despite all the fun the evening ended a bit after 11pm and getting-up today was an interesting moment.
Bass slam and WAF are too high to measure. We are supremely grateful to the designers at Zu Audio. They hit a Grand Slam with these speakers and I caught the pitch without any gloves on!
Some tube rolling in my Grounded Grid revealed that the Electro Harmonix 12AU7 outclasses the JJ 12AU7. My LP12 setup also worked very well. Now I need a new Phono Stage. Heck, I will just build one myself.
Has it been that long since the Druids arrived? Well guess what, I now have a Mini-Method sub. The combination is spectacular with the lowest registers coming through like a Halogen Lamp on a Foggy evening.
More testing is underway. But for now I can tell you this. The BEST integration I have heard so far, and I have connected the Mini-Method to my Preamp outputs (in parallel with the amp outputs) is going via my Harman Kardon A500 Ambience output. This is a summed center channel output that enables the Druids and the Mini-Method absolute phase and musical harmony.
I had to fool around about 45 min to get the bass to gel via the traditional High Level Preamp to sub connection scheme. I find that powering the sub with the power amps sonic signature makes for a better system match. Nevertheless, we will continue our quest for the perfect match.
HIGHLY RECOMMENDED FOR DRUID and TONE OWNERS. $999 ON SALE AT ZU, HURRY AND DON'T MISS THIS SALE!
Knowing me... I would not leave you out on any nice ideas I come-up with, especially when they were used decades ago in Vintage Stereo amplifiers. I have illustrated the issues that arise from connecting the Subwoofer's internal amplifier directly to the Preamp outputs, thus bypassing the main Stereo amplifiers. You can see this illustrated in the 2 diagrams I made below.
To me and my ears, the Mini Method sounded best when connected via a Summed Amplifier Sub Output and Level Control.
PROJECT PARTS LIST:
(2) 33KOhm 1 Watt Resistors
(1) Set of Tag Boards and solder wire
(1) 1.25K to 5 K Potentiometer (1 or 2 watt) - (2 pieces) FOR STEREO VERSION
(1) Control Knob - (2 pieces) FOR STEREO VERSION
(1) RCA Female Chassis Mount Connector - (2 pieces) FOR STEREO VERSION
(4) Sets of Speaker Binding Posts, the better the better. I like Vampire Connectors, they are tough and don't strip at all.
(1) Project Box (8" x 6" x 2") or larger if preferred. Best to use the heaviest box possible to weigh-down the speaker cables.
(3') Your favorite speaker cable for internal wiring and external hookup. I used Zu IBIS 2m pair, also QED Silver Anniversary or Van den Hul JADE for starters. Cardas Speaker cables are also amazing as are TARA Labs and finally Nordost.
(1) Short set of TERMINATED speaker cables to connect the Amplifier output to the Box. Mono-Blocks may require longer jumpers.
Here's the diagrams I made to illustrate what I describe. Not that the first diagram will not work, but it's much harder to adjust in my experience. You seem to have to fool around with Phase, Level and Crossover to get this just right. With the method I propose, you simply run a single 6ft RCA (F) to RCA (F) cable between the box and the powered subwoofer and drive the box with the main amplifiers to generate the drive voltage for the Subwoofer. You can set the Subwoofer level control to "Max" and simply use the control on the box to adjust the subwoofer level(s). Practically no need to adjust the Phase to 180º, initially leave at 0º as the speaker and the drive signals are already in phase. The crossover control is the only thing left to tweak. I am lucky that the Druids work excellent at 40 Hz with the Mini Method.
THIS PICTURE SHOWS A TYPICAL HOME-THEATER POWERED SUBWOOFER CONNECTED TO LINE LEVEL PREAMP SIGNALS. THE CONNECTION IS MADE FROM TO SUB-WOOFER LINE LEVEL INPUT FROM THE PREAMPLIFIER CIRCUIT IN A HI-FI SETUP. MOST PEOPLE DON'T HOOKUP THE POWERED SUBWOOFER TO THE HIGH LEVEL CONNECTIONS ANYHOW AS IT'S TOO MUCH OF A HASSLE TO DEAL WITH THE USUAL CHEAP PLASTIC CONNECTORS ON MOST UNDER $1K SUBWOOFERS. YOU CAN SEE HERE THE COMBINATION OF THE DIFFERENT SONIC FINGERPRINTS. ONE SIGNAL PASSES FROM THE SOURCE, THROUGH THE PREAMP AND DIRECTLY TO THE SUBWOOFER AMP. THE OTHER TAKES THE SOURCE SONICS AND PASSES THIS THROUGH THE PREAMP AND AMP CIRCUITS. THEREFORE ONE ENDS UP WITH DIFFERENT SONICS. THIS SETUP IS MORE OF A CHALLENGE TO MATCH PROPERLY, BUT RESULTS IS SATISFACTORY PERFORMANCE. I AM NOT SAYING THAT THIS METHOD DOES NOT PROVIDE EXCELLENT RESULTS. BUT I FOUND IT MUCH EASIER TO LIVE WITH THE SOUND OF A SPEAKER LEVEL DRIVEN SUBWOOFER VS. PREAMP LINE LEVEL DRIVE SEE THE FOLLOWING DIAGRAM THAT SHOWS THE SECOND ALTERNATIVE.
I PREFER THIS METHOD AS IMPLEMENTED IN THE HARMAN KARDON A500 AMPLIFIER. THE SUBWOOFER CONNECTION CAN BE MADE FROM A 'SUMMED' POWER AMPLIFIER OUTPUT CIRCUIT. THIS METHOD PRESERVES AND TRANSFERS THE SONICS OF THE MAIN AMPLIFIERS TO THE SUBWOOFER. I THINK THIS SOUNDS MORE MUSICAL TO MY EARS, NEVER LUMPY OR DISCONNECTED SOUND. THE WORD THAT COMES TO MIND IS "SYNERGY." YOU TELL ME WHICH ONE SOUNDS BETTER....? I WOULD VENTURE TO SAY THAT THE SUMMED OUTPUT METHOD IS SONICALLY SUPERIOR BUT THIS IS A SUBJECTIVE STATEMENT. I KNOW THAT HI-FI NUTS WILL CHALLENGE THE QUALITY OF THE RESISTORS USED, THE DISTORTION CAUSED BY THE LEVEL CONTROL AND MANY OTHER TWEAKY AND NEUROTIC ISSUES SUCH AS PLACING AN ADDITIONAL SMALL RESISTIVE LOAD ACROSS THE MAIN AMP OUTPUTS. ONCE AGAIN MOST POWERED SUBWOOFERS COME WITH THE CRUMMIEST SPEAKER CONNECTORS THAT DON'T ALLOW THE USAGE OF THE BEST SPADES AND BANANA INTERFACES, MOST ARE PUSH-IN TYPES, OR AT BEST EASY TO BREAK SCREW-ON'S THAT ALMOST REQUIRE YOU TO STRIP THE SPEAKER CABLES BARE. BY MAKING YOUR OWN INTERFACE BOX WITH PREMIUM SPEAKER CONNECTORS, ALL YOU NEED IS A SMALL JUMPER FROM THE AMPS TO THE BOX OF THE SAME SPEAKER CABLE USED, WIRE THE BOX INTERNALLY WITH YOUR FAVORITE SPEAKER CABLE AND CONNECT THE SPEAKERS TO THE SUBWOOFER BOX AND BINGO! WE PRESERVE SYSTEM SONICS AND KEEP THE FANCY SPEAKER CABLE INTERFACES INTACT. YOU CAN TAKE AN ADVIL NOW.
LAST BUT NOT LEAST A STEREO VERSION OF THIS SETUP FOR THE LUCKY FEW WHO HAVE "TWO" POWERED SUBWOOFERS FOR STEREO BASS.
There's something about "POWER"......,
Over four decades ago, home loudspeaker systems were commonly available in 16 Ohm impedances. The reason why the music industry no longer offers 16 Ohm loudspeaker systems today has to do more with profit rather than with sound. With the advent of holy-grail solid state amps that deliver greater power into smaller impedance loads, high impedance speakers went against the marketing plan.
Suddenly we were thrust into the realm of High-Current. The Audio market had a great sales pitch for a 100 watt amp into 8 ohms that delivered even more power into 4 ohms and even more power into 2 Ohms... etc. etc.. the dawn of the "I have a 1000 watt stereo system." Now ask the person who claims to own a 1000 Watt amplifier to define what a Watt is......
Speakers that will cause a Solid State amplifier to deliver greater output power figures are good for audiophiles who don't understand Power and Watts in the first place, and also great for stores that take Visa or American Express!
Imagine trying to sell to a 'typical' neophyte customer the idea that his 'new' 100 watt per channel amplifier will 'only' deliver 80 watts into 16 Ohms, and even less power into 32 Ohms and so on. Yet with 8 Ohm speakers you get 100 Watts, 4 Ohms lands you 120 watts, all from the same Solid State amp. The ego starts to rise and the power plus distortion follow suit.
The reality remains today the same as yesterday. People continue to tout their audio systems virility in terms of hundreds and sometimes thousands of watts, absolutely ridiculous, yet very difficult to explain to someone with poor mathematical skills. This is the most ridiculous misunderstanding of how amplifiers deliver power, and also how much actual power a given amplifier delivers to a speaker. I go even further, we have to get into how much power one actually needs at home. The market has been made FAT by inefficient speakers, but today we are seeing a new trend, Sub-Woofer based systems with flea sized mid and upper frequency drivers. What's actually going on here?
What people never learned is that the first watt is the most important one, not the watts that follow. Unless you own a video-music bar, a for hire music service, or a Video and Rock pub, 300 watt amps are not really the best solution for a typical home, unless you like the sound of inefficient speakers with lousy impedance characteristics. Yes we have a small market for 5 drivers speakers that can split concrete foundations. Yet ignore me if you like Eminem, Reggaeton, RAP, Death Metal or sub-sonic stomach turning Bass, you guys need 500 Watts RMS per channel amps and $15,000 USD speakers to meet your requirements, nothing wrong with that. At least I find no flaws, yet I would assume that my listening period would be cut short.
I am not into power, I prefer music. Judging from the rattling license plates on cars, most folks are not into Hi-Fi, but prefer sonic fireworks, graphic equalizers and tone controls. Most people prefer sound with interesting lyrics in the background, very few can listen to instrumental music. Often the only musician on some albums is the one mixing the final tracks, the recording engineer. I guess today we can agree that Bass is a fundamental requirement in reproduced music for the newer generations. No criticisms here, just an observation on how modern electronics and technology has improved full range sonic performance. I am not an old goat, I myself once cranked-up Black Sabbath to ear splitting levels on 15" Cerwin Vega speakers.
Thrilling, yes.... Hi-Fi, probably not.
The other day I was at a Xmas party when the host pulled me over to see his new toy. A flea sized SONY home theater system that he claimed had 1000 watts of power. To me this means that this system, the size of a small Notebook PC must have had at least five internal and separate 200 Watt amplifiers into 8 Ohms that together made the 1000 watts or some other scheme, probably not! The power rating was as inflated as the Hindenburg.
1) Lack of understanding about music, power levels, the Decibel and electrical circuit theory
2) Little knowledge about Ohms law
3) Forgot totally everything once learned in Trigonometry class, SIN, COS, TAN, Unit Circle....
It's always been an obsessive need for Hi-Fi system owners to compare their audio systems merits on Watts alone.
It's like comparing cars based on top speed only.
Why do people firmly believe that more power is better than less power when typically most amps that deliver more than 100 Watts per channel
good enough for 80% of applications. Let's work some 'electrical' math and gain insight into how many watts that person really has at his disposal.
The BASIC formulas for calculating DC power in ELECTRICAL circuits are:
DIRECT CURRENT CALCULATIONS (START HERE AND WORK YOUR WAY TOWARDS AC CALCULATIONS)
(1) Power = Watts = Voltage ² / Resistance = V²/R
(2) Power = Watts = Voltage x Current = V x I
(3) Power = Watts = Current ² x Resistance = I² x R
YOU HAVE TO MEMORIZE THESE FORMULAS. FAILURE IS NOT AN OPTION.
THESE ARE THE BASIC BUILDING BLOCKS FROM WHERE YOUR KNOWLEDGE OF ELECTRICAL CIRCUIT
THEORY WILL STAND. THE BETTER THE FOUNDATION, THE FUTURE WILL LOOK BRIGHTER, MUCH BRIGHTER.
AC WORLD so go (GRAB your very own, lost in the drawer SCIENTIFIC CASIO, HP OR T.I. also try and recall your HIGH SCHOOL TRIG. TEACHER'S NAME... hummmmm.)
(1) Complex Power; S = V * (I*) ; The Complex Conjugate of Current is required to define power and also properly account for the reactive load, whether (-) capacitive or (+) inductive.
Its basically an XY graph with three possible arows. The X axis, the Y axis and that thing we engineer's like to commonly refer to as the Magnitude.
So...... (have a beer now). We can calculate the 3rd piece with any prior to measurements, etc. This is the Power formula. A special graphical representation exists called The Circle Diagram. This gives in one page, the whole tamale.
You see when a piece of equipment draws power, it will consume this as two vectors of power offset by a phase angle.
If you have a pure capacitor or pure inductor, these reactive loads will exhibit a specific impedance based on the frequency that the power being transferred into the load has.
We then have Capacitive Reactance and Inductive Reactance. Lest not forget the grand-daddy of all, Resistance and Voila another triangular, simple to solve set of equations. Some folk's measure and plug the values into the formulas. While other's design their life away and then tweak the thing into a real prototype.
Now back to Power Transfer, let's say you live in a home. You pay your electric bill, right??, I hope so.....
Your main breaker or fuse panel will have a specific rating and design. In a typical residence today, you will want nothing short of AWG2 cable to feed your house. 1/0 and now you'r a' talkin.
Now the painful part, some math....
S2 = P2 + j Q2 (Pythagoras Theorem);
S is the symbol we use to describe Complex Power, or the Hypotenuse of the Power Triangle.
P is that Stove a'cookin, heater heating, blow dryer a drying power.
Q is the reactive power. This is a funky storage thing.
Capacitors charge-up and Inductors fire-away.
Each do the polar opposite and in a 90º way.
You typically plot the Inductive reactance on the + Y axis and the capacitive reactance on the -Y axis. The formulas to determine the reactance of an inductor or a capacitor will be:
Xc= - 1/2π*f*C
Xl = 2π*f*L
f = frequency. In my case for my home power is 60 Hz, a constant 24/7. Always 60 Hz (+/- 3%)
Let's calculate for some inductors and capacitors at 1000 Hz (that dog barking, ear piercing 1000 Hz... ughhh ) or better yet, let's imagine that I hook-up this inductor to my wall socket and see if it hold's (scary stuff).....
L = 5 Henries; but an inductor has other relevant parameters such as DC Resistance in Ohms. So.... we can conclude that even an inductor has a Resistive component and also an Inductive one. There's now way around this as the wire that we use to wind-em-up has DC resistance. But this resistance is of the Distributed variety. There are basically two way's capacitance and inductance can exist. Lumped or Distributed. Lumped is akin to a cap, mica pico cap, resistor, etc. The specific measurement of a multi-terminal device. Distributed anything is basically the accumulation of that parameter based on length, width, thickness, etc.. of the component, it's the physical size that sets the value of Capacitance or Inductance. Hence a 60 mile long power company electrical service to Shangri-la, will be on the order of 3.5 Megawatts.
At 3.5 Megawatts, we have 3.5 x 106 Watts; a.k.a. = 3,500,000 Watts (3.5 million watts)
And the town is running a power factor of 0.87, or the Cosine Inverse of (0.87) = 29.54º Phase Angle.
With this I can resolve that town's power consumption to it's real and reactive parts;
3.5 * Cos (29.54º) = 3.5 * 0.870 = 3.05
3.5 * Sin (29.54º) = 3.5 * 0.493 = 1.73
We now have our Power Triangle completed!!!!! You can clearly see that a typical home behaves like a large resistor and inductor, almost never a capacitor. I'm sure that the power company would come and investigate a purely resistive-capacitive home, if they have the patience to sniff it out.
Now let's focus on a tube amp power supply. The value that the rectifier sees when a power supply inductor is smoothing the power is the following;
Inductive reactance is based normally on 120 Hz in tube power supplies, or double the frequency of the AC Mains that happens when a Full Wave Rectifier rectifies 60 Hz AC, it gets doubled into 120 Hz all positive or negative going cycles.
Xl = (2) * (π) * (120) * (5)
Xl = (6.28) * (120) * (5)
Xl = 3768 Ohms Reactive Inductance
Now let's calculate a capacitor at 1000 H;
C = 0.1 uF (or One Microfarad)
Xc = - (1/2pi * f * C)
Xc = - (1/ (6.28) * (120) * (0.000001)
Xc = - 1326.96 Ohms Capacitive Reactance.
This means that as long as you know the phase angle, you can back-calculate the power equation into it's real and reactive parts. This is vector math again for the one's looking at the arrows and saying w.t.f..
In AC Circuits, everything changes as the Voltage and Current's are moving (well let's say they wiggle or oscillate). In the US, power is generated at 60 Hz (or 60 Cycles per second). In the rest of the world power is typically generated at 50 Hz and also at 60 Hz. It's typical to find countries who deliver both 120V and 220V Single Phase, but never at different frequencies. I blew a wall wart in Brazil once on a 120V outlet wired 220V!
In the AC world there are also specific means to determine, mathematically, the direction of power flow. This enables the formula's results to say who is Generating power and who is consuming (or storing as in Reactive Circuits). Such a deep analysis is not really required here as we know that an amplifier is a power generator and a speaker system is a power consumer, well after the amplifier has consumed electrical mains power to convert this to music power.
The main difference between DC and AC calculations is that AC electronics requires the usage and understanding of Vector Analysis and/or some basic Trigonometry, while DC formulas don't have this extra hassle to deal with.
The reason for this vector dependence has to do with the nature of Alternating Current vs. Direct Current;
In AC circuits the presence of alternating current (i.e. 60 Hz in my world) requires vector mathematics due to the fact that the nature of the electrical energy is sinusoidal, or varies in frequency over time. DC circuits do not have frequency variations as f=0. Therefore we need to depend on a calculator, the Unity Circle and SIN, COS and TAN trigonometric functions to determine Amplitude, Phase and Magnitudes.
DC Power is a Scalar in DC Circuits but is a vector component in the X axis in AC Math. The very nature of AC power delivery is that we can 'transform' power using transformers to boost the voltage and reduce the current losses in the transmission lines. In small equipment this is not relevant, but at 30 to 50 miles, transmission lines can 'soak-up' power and reduce efficiency.
SAMPLE CALCULATION BASED ON DC MATHEMATICS; 100 WATT AMPLIFIER INTO AN 8 OHM TEST LOAD RESISTANCE
Let's solve for the DC Voltage required to dissipate 100 Watts of Power into an 8 Ohm non-inductive resistor.
This is purely a DC calculation based on the fact that if we have a 3 variable equation and know 2 of the three we can always solve for the third missing value.
No amplifiers here, simply a DC circuit with an 8 Ohm power resistor capable of 100 watts power handling.
(1) Power = Watts = V² / R; P = 100 Watts and R = 8 Ohms, i.e. what is the voltage required to dissipate 100 Watts into an 8 ohm resistive load?
We solve for this "DC Voltage" by dividing both sides by 8 Ohms and taking the square root of both sides to clear out the squared term on the voltage we end up with:
(1a) V = Square Root [Power * Resistance]
Voltage = Square Root [100 Watts * 8 Ohms] = Square Root [(800)] = 28.28 Volts DC
Using Ohm's law the resulting DC current flow can be calculated by solving for current (I) in Ohms law V = I*R.
I = V/R; 28.28 Volts / 8 Ohms = 3.53 Amperes, enough to blow a 3 amp fuse in a transformer primary! A.K.A. Speaker Frying Land!
I would protect these speakers with a 3 ampere 'Slo-Blo' fuse in line with the speaker cables. Music is not continuous but if one let's go of the Volume Control, a 3 amp 'Slo-Blo' fuse is cheap insurance for the speakers.
My suggestion is to be skeptical about any 'inflated' amp and speaker power claims very closely, especially from people who don't know the difference between a Watt and a Volt.
An amp delivering 1KHz at 100 Watts will cause the neighbors and the dogs much grief.
At 18 KHz the dogs will go absolutely bonkers!
Always use a resistive audio dummy load for these electronic 'Viagra' tests, or wear ear protection.
I must mention that the formulas above are not 100% true for speakers as they themselves are a complex resistive and reactive load. There are voice coils and crossover components that make the voltage and current go out of phase and cause energy storage and phase angle issues that can damage amps, woofers and especially tweeters. This is why AC Mathematics is required to correctly model a loudspeaker.
Now we need to introduce a term often misunderstood by many, it's the term IMPEDANCE. Basically in layman's terms IMPEDANCE is analogous to RESISTANCE in the AC world.
The nature of an IMPEDANCE consists or a load made up of one or more combinations of RESISTANCE, INDUCTANCE AND CAPACITANCE.
RESISTANCE is the simplest to learn. It's units are measured in Ohm's and the VOLTAGE & CURRENT are always in Phase, i.e. 0º Phase Shift here, hence the simple math involved.
Now if we introduce an Inductor, STOP
As to how much continuous power any speaker can handle, there are phase angles involved and the math become much messier. Difficult speakers are those whose phase characteristics vary significantly from the nominal impedance, and the variation is lower than the nominal value. Tube amps suffer when a speaker goes significantly capacitive while dropping below 4 ohms.
The above issues relate to model of an 8 Ohm, 100 Watt resistor (non-inductive) being tested at 28.28 Volts and 40 Volts respectively. Peak to Peak voltages would be 2.83 times these values, or 28.28 * 2.83 = 80 Volts AC Peak to Peak, the same applies for the 200 watt model, 113.2 Volts AC Peak to Peak (as seen on an oscilloscope CRT screen from the tip of the positive waveform to the bottom of the negative going side of the sine wave.
If you ever measure more than 28 Volts RMS continuously across a speaker the size of a small shoe-box, make sure that you have the warranty card handy and get an RMA number. Unless of course ...the speaker is rated at 100 Watts continuous, when most small boxes cannot handle the power.
Walmart, Costco, Kmart, Best Buy and Circuit City all sell 'All-in-one' Home Theater Systems that get the job done, stick to this and forget about the inflated specs in the brochures. I would venture to say that testing of these systems will show s significant deviation from published specs. And now that these companies are not getting their products scrutinized, these money saving systems definitely cannot provide the power that people claim they have.
But unless it's a Sharp branded 'Class D' amplifier which can and does deliver hundreds of un-distorted watts, the latest technology is expensive. These amps cost about 2 to 3 thousand dollars and weigh about 2 pounds each. Price and weight do not correlate to power, yet the technology of Class D operation does. One should finally give people the speaker busting power they all crave and Class D seems to be the new solid state kid on the block. Let's see what these products turn out to be in the next several years.
With power as with life, too little or too much may not be a good thing. It's best to own a system that can satisfy the size of the room it's in. Don't buy 200 watts of power for a room that is 8'x10', 50 watts is enough.
Manufacturers play with power specs that are often Music Power. Music Power is 3 or 4 times higher than a real 'continuous' power rating for any given amplifier. So when you buy that 500 Watt system, expect about 125 to 160 watts composite power for all driven channels. Unless it's a McIntosh AC-3 rated 6 Channel amp that does deliver 200 Watts into 8 Ohms Continuous power (40 Volts RMS across an 8 Ohm resistor.... 5 amperes!!! wowiee)
If you ever buy a piece of equipment that claims to have 500 watts per channel, make sure that it's continuous power into 8 Ohms. Also check if the rating is the sum of both channels, or 250 watts per channel to equal 500 watts total output power both channels driven. Specifications can be misleading and are often worded in such a way as to create an impression, not convey an actual technical parameter.
Also note that amplifier power ratings, measured at 4 Ohms in Solid State amplifiers with no output transformer will mean less power driven into 8 Ohms and even less into 16 Ohms, on and on....
The purpose of these explanations is to clarify reality for people who think they own 1000 watt stereo systems. More often it's really t a Home Theater amplifier system that implements 5 x 50 Watt modules in a nice shiny box with nice buttons and a digital display. Good looks yet overzealous specifications. The best indicator of how much power a given amplifier has is to look at the value of the mains fuse. The larger the more apt to have massive power outputs. Except for some designs like Carver who have a more efficient means of converting power supply energy into music power.
Bear in mind that one can easily expose oneself to sound levels both at home and music clubs that permanently cause damage to one's hearing. So the next time you crank-er-up, or stand near a large monitor speaker at a watering hole, make sure you are able to keep your exposure to sound levels under +96 dB. You need to buy a sound level meter for this or simply move farther away from the music sources. Our hearing is much more expensive to fix than a stereo system. I end my discussion here with a simple one liner that sums up the ideas I wanted to examine in further detail;
"Without mathematical proof, perception is a valuable marketing tool"