The Wizard Of AWEs

Andrew Chasin interviews the man behind Coincident Speaker Technology, Israel Blume

Israel, how did you get involved in loudspeaker design?

Coincident Speaker Technology and its predecessor, Concentric Speaker Technology was created because of my personal ultimate dissatisfaction with every speaker system I owned or auditioned. In my 25 years in high end audio, I owned most of what are considered to be the finest speakers, i.e. Quads, double Quads with Decca Ribbons, Acoustat X,II,III, II & II, Quad 63, Wilson Watts, Martin Logan CLS etc. Not any of these aforementioned speakers were well enough balanced to keep me happy in the long run. It was after extensively modifying a pair of Watts and in the process significantly improving them, that I became convinced that it was now necessary for me to design and build a speaker from the ground up.

Your first speaker, the Concentric Monitor, had low efficiency, was costly to build and was housed in a cylindrical enclosure. How did this design evolve into the efficient, relatively low-priced, more traditional box speaker that is the Conquest?

There is a very significant interim stage between the Monitor and the Conquest and that is the Troubador loudspeaker and the subsequent models that were constructed from our patented AWE (Asymmetrical Wall Enclosure). Using extensive computer modeling I was able to duplicate the sonic properties of a cylinder by the use of non parallel flat planed walls. The most significant advantage of the AWE is the elimination of internal standing waves. The speakers that ensued, the Troubador, Troubador Grand and Digital Master all incorporated this type of enclosure with results that have been widely admired.

In an effort to create a more affordable loudspeaker, the labor intensity of the AWE series of loudspeakers precluded this, the Triumph and eventually the Conquest were developed. In designing these speakers, all the same principles of the AWE speakers were incorporated with the exception of the non paralleled wall enclosure. While the enclosures of the Triumph and the Conquest look fairly conventional they are anything but ordinary.

The Triumph was developed to provide the audio world with a sub $1000 pr. loudspeaker that would sound as good or better than competing models costing 2-3 times the price. The Conquest was the logical evolution from the Triumph since we now wanted to create a floor standing version of the Triumph that would go lower in the bass due to the use of an 8" woofer instead of the 6 1/2" unit of the Triumph and because the internal volume of the Conquest is 45 liters versus 16 for the Triumph. An added benefit, the Conquest is 2db more sensitive than the Triumphs. We strongly believe that the Conquest is the finest sounding and best built speaker that can be purchased for under $4000 pr.

Cabinet design is obviously something to which you have dedicated much of your R&D effort. How is your patented Asymmetrical Wall Enclosure different from asymmetrical cabinet designs from companies like NHT and others?

Our AWE speakers not only have no walls parallel to one another (which the other speakers you refer to do not), the enclosures are additionally constructed out of an inherently non resonant material and tuned to a high fundamental resonant frequency.

Given that an AWE is not employed in the Conquest, how are internal standing waves dealt with in that speaker?

Enclosure dimensions were computer calculated to reduce resonances and internal reflections. The enclosure dimensions are equally significant in minimizing internal standing waves.

Without giving away too many trade secrets, tell me about the materials used in your cabinet construction and describe how you get away without using any internal damping.

In a determined effort to minimize resonances and maximize rigidity, a specially selected 1" hardwood MDF is used. The enclosure additionally is tuned to a high fundamental resonance frequency of 350 Hz. This high resonance frequency is not only sonically benign but it precludes the use of soft, spongy materials within the enclosure. Such materials are sonically deleterious due to the creation of internal reflections. Extensive testing and computer modeling in addition to countless hours of aural auditioning lead in the direction of enclosure tuning as opposed to the use of damping techniques. Our research has confirmed that it is far preferable to use an inherently non resonant material and tune it to a high fundamental resonant frequency than attempt to damp a low fundamental resonant frequency.

After experimenting with countless enclosure materials (i.e. granite, polymer composites and various thicknesses of fiber boards) it was ascertained that contrary to popular belief, thicker and denser is not only not always better, in virtually all cases higher mass significantly degrades sonic purity. The reason is as follows: It is a given that all substances have a fundamental resonance at a particular frequency. The higher the mass, the lower the fundamental resonance frequency. The type of material chosen will further determine the amplitude of that resonance. Resonances occurring under 100 Hz are impossible to damp sufficiently so that they are not audible. The common practice that most speaker manufactures use in an attempt to deal with these types of resonances is the application of heavy amounts of soft, absorbing materials. This however, creates more sonic anomalies than it cures. These reflections not only cause signal slurring from the drivers, but furthermore impair linear piston motion of the drivers. Transient slurring, increase in internal standing waves causing mid bass muddiness or alternatively mid bass suckout are the sonic by products of using damping materials in a speaker enclosure. As a further penalty, speaker sensitivity is diminished as well.

The approach taken for the Conquest's enclosure was to use an inherently minimal resonant material and further tune the resonance to an even higher frequency so that its amplitude would be low thereby obviating the use of damping materials. The end result is an enclosure with very little sound of its own.

As far as Coincident's drivers are concerned, do you design and build them in-house or do you source them externally?

They are sourced externally but some are built to our specs while others are heavily modified to significantly improve not only their sonics but their power handling capabilities and minimizing cavity resonances.

Can you give me any hints as to your future product plans?

At the moment things are very hectic here at Coincident. In the last 12 months we have developed and brought to market 11 models of speakers. At times I am amazed myself. We therefore do not anticipate much in the way of new product development for the rest of the year.

Thanks for your time Israel.

My pleasure.