High end audio enthusiasts who love their low powered tube amps often look to pro audio for high efficiency speaker components. Most high end speaker designs are not efficient enough to produce quality sound at a reasonable volume level when paired with a low powered amplifier. Planars, electrostatics and the bulk of high end speakers using standard dynamic drivers need anywhere from 20 up to hundreds of watts of power to sound their best. Pro audio drivers on the other hand allow one to design a speaker well over 90db and possibly over 100db efficiency. This matches up with the low powered tube amp quite well. There also is a growing movement of people interested in low powered solid state amplifiers such as the First Watt line by Nelson Pass of Pass Labs fame. As an owner of a First Watt F6, there is certainly some similarities between the low powered tube amplifiers and this low parts count, as simple as possible approach to solid state amplification. The theory behind this is if the first watt sounds bad, why would I want 400 of them?
Using pro drivers for home audio is nothing new of course going all the way back to the early horn speakers of RCA, Western Electric, Altec and JBL. One major difference of note is that speakers using a compression driver and horn normally need the horn to be padded down quite a bit to match the output of the mid/bass driver. Compression driver horn combinations can often have efficiencies in the 105-115db range and need to be padded down with an l-pad, resistor or autoformer to match the 95-101db of the bass driver. There are ways to bring the efficiency of the bass driver up as well by using horn loading or adding more bass drivers. These systems can get physically large very quickly chasing the highest efficiency so this must be a consideration depending on the room they will be used in. Most who have heard this type of system would agree that there is no substitute for cubic inches when it comes to conveying raw power and the physical movement of air that these systems can bring. With the advancements in compression driver and horn design of the last few years these systems can be built to convey this physical power and still have the excellent resolution, timing and soundstage depth of more traditional high end speakers.
As an amateur bass guitar player who has spent a good deal of time around many different instruments, I have a tendency to be able to pick up instantly that I am listening to a speaker system rather than the real thing by noticing the lack of physicality of the speaker system. When someone strums even a standard acoustic guitar in a room within say 15 feet of the listener, there is a good deal of air movement from the resonating body of the guitar that you feel as much as you hear it. This quality is missing from most speaker systems I have heard. You simply cannot move much air with the relatively small cone drivers of conventional speakers. This of course is a personal taste as obviously many listeners prefer to have the very best resolution and simply accept the fact that they can get close to the real thing as far as what they hear without the charged air feeling that real instruments bring. Anyone who has stood near a grand piano as its played knows what I mean. It is pretty tough to reproduce that kind of power with diminutive home stereo speakers especially in an open floor plan home. And I am not talking about the low bass. The lowest notes are relatively easy to reproduce using an array of subs, I am speaking of the presence in the upper bass, lower midrange that is a dead giveaway whether you are hearing an instrument or a recording.
My audio journey has sort of come full circle over the last 45 years. I have been lucky enough to own many different systems that all did one or two aspects of reproduction well. I started out in the early 80’s with a Yamaha receiver pushing huge Cerwin Vega D9’s. Sure they rocked but not exactly high end as far as resolution, soundstage etc. From there moved on to Altec model 19’s driven by many different amps. Again plenty loud but definite disconnect between the horn and 15 inch driver. Should have played with crossover designs but did not. Later I moved on to Wilson Watt Puppies driven by an Audio Research tube amp. Amazing resolution but always felt I was listening to high quality studio monitors rather than instruments. Had big Acoustat electrostatics and Magneplanars driven by large solid state amps, again amazing resolution but somehow sounded ghostly, not enough physical presence to convince me I was hearing real instruments. Remember this is all in a large open floor plan of close to 2000 square feet. I firmly believe some of these systems would have been just fine in a closed say 16×20 foot room. Current system is sounding good but of course not there yet. Driving a full range 8 inch with an SEP amp. This is matched up with a pair of monitors comprised of the Purifi 6.5 and Dynaudio Esotar t330d tweeters fed with the First Watt F6 single ended solid state amp. Then a 10” pro woofer on each side driven by their own 600 watt class D amp. All in a 12” x 26” foot print speaker. Actually sort of look like the Watt/Puppies. This is closer to what I am after as far as resolution and depth of stage, except again the movement of air and palpable presence of real instruments is not there in my large room.
Sincerely hoping my next speaker venture will be the last. After an inventory of the drivers collected over the last 40 years it occurred to me that I have most of what I need to make a no holds barred assault on the high efficiency state of the art similar to what Lynn Olson and Gary Dahl are after in the epic “Beyond the Ariel” thread on DIYAudio. I have a pristine pair of Altec 414a twelve inch drivers that will be ran up to 700hz then crossed over with only a cap and coil to a 18 Sound ND3SN 1,4” compression driver mounted on xt1464 horns and padded down using autoformers. These will be mounted in roughly 3 cubic foot cabinets and will sit on top of a pair of lower cabinets discussed next. These will be driven by the tube pre and SEP amp. Separate lower cabinets will be roughly 20”w by 30”d by 26”h and will house an Altec 416b in the front half with a dividing wall internally. A Faital Pro PR450 will be side mounted in the back half of this cabinet firing to the side. Internal volumes for these are a little low but I will experiment with aperiodic loading as Gary Dahl has. EQ will be needed regardless to bring the bass up for both the 416b and PR450. The 416b will be powered by the First Watt F6 initially to determine if 25 watts is enough. The PR450 will be powered by its own 600 watt class D amp and will handle the lower bass. 416b will only run down to 50hz or so. I am hoping this amount of cone area will give me the upper bass lower midrange air movement that is missing. I have read of others systems that use as many as 4 or 8 fifteen or eighteen inch drivers per side! My speakers will be in the family living room so maybe someday after winning the lottery and have a dedicated sound room. As planned these speakers will be less than 50” high by 20” wide by 30” deep. Fairly small footprint considering they are housing a horn, a 12 inch driver and two 15” drivers.
I truly wish that my obsession with the fundamentals and physicality did not exist but seeing as I already have all of the drivers why not give it a go? A system should be able to convey the power of the instrument without the volume level being so high that it sounds unnatural. This goal requires a large amount of cubic inches of quality high efficiency dynamic drivers. This system as well as the one I am listening to currently requires the signal to be split 3 times. After much experimentation I have concluded that this does not degrade sound quality in any noticable way when using high quality OCC y adapters.
Cabinet construction is another highly debated topic that deserves its own section in this forum. I have owned cheap flimsy cabinet speakers all the way up to the Wilsons dead as can be cabinets. After all the speakers I have heard over the years I have come to the conclusion that I prefer what high enders refer to as a musical speaker rather than an analytical speaker. Just my personal preference and willing to concede that part of what I am hearing is likely cabinet colorations, but I just don’t connect emotionally with the completely dead wall cabinet style of speaker. Right or wrong I will take the made of natural wood Sonus Faber approach versus the phenolic resin or granite structures of speakers that take the Wilson approach.
Those that have been in the audio field for a good length of time know that every component and every system is basically a series of compromises. From what I am reading I have high hopes that the next system will not sacrifice any of the positive attributes of my current system while addressing the issues I do have with it. I have accepted the fact that much tinkering will need to happen to blend the horn seamlessly with the 414a. Lots of measuring and adjusting to get a flat response on the horn is in order for sure. This is the biggest reservation I have is whether I will like the compression driver/horn treble as well as I like the soft dome Dynaudio Esotar. I do have separate volume control for the three amplifiers so will be able to match the different sections together as I am doing now.
I did not intend to ramble so long about my own system, but it is one example of how pro audio high efficiency speaker components are being used in a home audio scenario. I hope others will share their experiences and systems in this forum as well as participate in healthy conversations. I will include what I hope is a comprehensive list of links to other forums as well as manufacturers, distributors and retailers of quality components.