To my best knowledge, it's appropriate to
credit three persons for inventing the multiple or distributed sub
array: Dr. Floyd Toole, Dr. Earl Geddes, and Todd Welti. Duke
LeJeune is an early adopter, studied w/patent holder Dr. Earl Geddes,
and Duke introduced me to Distributed Sub
Array.
Duke adds a unique
feature to his DSA (called Swarm): "Small" or "Domestic"
size rooms (as opposed to commercial size rooms), naturally boost
bass about 3 dB per octave <100 Hz. To counter or neutralize
this effect, Duke naturally tuned his subs for a mirror image of this
curve, w/acoustic roll off of about 3 dB per octave <100 Hz, or
about -7 dB @ 20 Hz.
All comments Re. performance
apply to a properly designed and well-setup distributed array.
DSA
has no perceived nor mathematical disadvantage for 2-ch music.
I've read much though not all of Toole's writings on the subject.
AFAIK Toole has written nothing suggesting a weakness for DSA in 2-ch
application. Properly designed and installed, transition to any main
speakers, regardless the architecture, is absolutely seamless and
transparent. DSA improves spatial performance in every way, and has
no downside except cost, hookup wire, and possibly larger foot print
(only about 11-3/4” x 14-3/4”).
Single amp crossover pole should be 80-90 Hz maximum. If a second amp is used, crossover pole may increase to about 150 Hz. In this case, the two subs closest to the front wall cross higher, while the two subs closest to the rear wall cross in the range of 70-80 Hz maximum.
I typed a text document about 1.3 pages, comparing DSA to four spinning propellers in a fish tank aquarium. Upon request I'll post it at my DEBRA web page.
Re. the “solvency” issue mentioned above relative to my one time selling Thorell guitars and not selling them now. I enjoyed selling the few Thorell guitars I did, and by mutual agreement with Ryan, decided to concentrate on my professional “wheel house,” being music and audio. (Downbeat Magazine reviewed my personal Thorell Sweet E guitar, which I latter sold. Some time latter, another client offered to buy the exact same guitar for a lot more than what he paid. When I asked the first buyer if he was interested in splitting the profit margin, he refused.)
Duke licenses me to sell DEBRA, which
functions identical to Swarm. Differences: DEBRA cabinets are about
1.75” wider and 1.75” less deep. Also, for $2990/five pieces
(four subs + kilowatt amp), DEBRA cabinets include a 3/4” solid
wood top panel w/round over on all four corners (under the solid wood
crown is 3/4” MDF veneered both sides). Also, my prices include maple, cherry, walnut, or satin black, whereas I believe Swarm costs extra for black (images to be posted soon of current production cabinets).
For $2800/set, subtract the solid wood crown w/round over, and all corners are square 90 degree.
Another difference is that all four DEBRA subs have only one pair of binding posts, while two of the Swarm subs have two pairs of binding posts and the remaining two subs have one pair of posts.
I credit Bob Carver w/giving me the idea for my setup advice, which has proven to work very well in a large variety of rooms. Without EQ of any kind, the worst case I have seen in any room is +/- 2 dB <100 Hz throughout the room, w/only minor “build up” in the most extreme corners. When one sub is ideally located in my current room, the FR window is 13 dB at the sweet spot, and extreme “hot spots” throughout the room.
Circa 2015, prices increased for the 10” ultra low bass driver. For the increased cost, cutoff now extends to 18 Hz.
Changes in cabinet construction circa 2015: Noble100's enclosures are 5/8” old growth Russian Baltic Birch ply laminated over 5/8” particle board for damping quality via its random shapes and sizes of wood chips. We switched to Duke's old cabinet maker (Duke moved from just north of me in ID to TX). Current cabinets are 3/4” MDF veneered both sides, with double thick baffle (1.5”) under the 10” driver, with a full “picture frame” brace just above the 10” driver. Recently we auditioned with 115+ dB peaks and no one including myself noticed any audible distress of any kind, in my 3300cf room.
Classic setup advice for one or two subs: distance between two subs and/or from any sub to the farthest main speaker should not exceed one quarter wavelength of the crossover pole. Conversely, with DSA, there is no “proximity effect” crossed @ 80 Hz, even with about 25 feet between two subs close to diagonal corners.
Strangely enough, as much as bass modes distort pitch, non-linear time distortion may be even worse and more audible. Bass modes can cause a particular bass note to linger or continue bouncing between boundaries long after the bass player on the program muted the note and played the next note of a different pitch. Listeners can and often do hear the two disharmonious notes playing simultaneously, where should be only one proper note.
Once listeners hear the difference of a system lacking this type of distortion, it's hard if not impossible to go back.
My last sound room had the equivalent of about $7k in acoustic upgrades and structural modifications, including a 3-sided acoustic ceiling soffit, w/mixed results at best. I paid $750 for the acoustic design alone. By huge margin the DSA outperformed the mods in that room.