DEBRA

Distributed-EQ Bass Reflex Array, 5+ pieces

$2990 USD + Shipping, Custom Finishes Available

No comparable commercial system, a unique solution from nature: the room’s preexisting fixed modes + four new “Golden Ratio” subwoofers = flat response and the smoothest, most musical and natural bass throughout the listening room. “Room Gain Complementary” tuning (Duke LeJeune) inverts the boundary curve <100 Hz. Unsurpassed pitch definition with the “elastic” qualities of bass in a commercial space.

No after-the-fact band-aid as per every other bass mode “cure”. No “hot spots”. No automated EQ. No acoustic treatment. No proximity effect.

Studio or home. A new state-of-the-art reference for music. Conservatively rated 113 dB @ 20 Hz for knockout HT punch.

  • Four reflex subwoofers each with 3 support cones + floor discs (2-piece cones terminate flat or spiked)
  • One Dayton Audio SA1000 Bass Amp: 1000Wrms @ 4-Ohms, active low-pass crossover, panel or rack-mount, single-band parametric EQ
  • Contact us for easy instructions to install subs in-wall
  • All orders custom, ship within 90 calendar days

 

 

 

Black driver panel faces the wall, spaced 1-3/8″. Requires three support cones not shown (included).

 

 

 

 

 

 

 

 

 

 

 

 

 

1-3/8″ thick black driver panel with crisp beveled edge rises 1/16″ above side panels. This panel faces the wall (spaced 1-3/8″).

 

Black baffles with drivers face the walls

Underside: port flare, terminal board, support cones

 

 

 

 

 

 

 

 

Underside: port flare, terminal board, support cones

In use at Cache Valley Food Pantry benefit/audio show, co-sponsors AudioKinesis and primeVibe, December 2010

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  • Frequency Response: 20 – 100 Hz (-3 dB)
  • Total System Weight: 300 lbs (amp, spikes/flats, four subwoofers)
  • Four High Output 10″ drivers, 2400Wrms total power handling
  • Sensitivity 91.5 dB/W/M @ 4-Ohms, one sub polarity inverted as per instructions
  • Unique qualities of bass reproduced in a commercial (large) space
  • Each subwoofer 67 lbs, 23.75″ x 14.5″ x 10.375″ (H x W x D) + support cones
  • Conservatively rated by designer Duke LeJeune for 113 dB clean output @ 20 Hz
  • “Room Gain Complementary” tuning (Duke LeJeune) + natural acoustic mode-canceling effect (no absorption/no resonators/no automated EQ) for the flattest, most natural bass throughout the listening room including corners
  • Three support cones + floor discs per sub, precision machined solid brass, durable black chrome finish, 86 grams each, 2-pieces terminate spiked (1-1/4″ diameter x 1-1/2″ tall) or flat slightly shorter

Four 10″ drivers, each:

17.1 lbs

600Wrms

Magnet 100 oz.

Xmax 12.3 mm

Voice coil 2.5″ 4-layer

Black anodized aluminum cone

Vented, triple shorting ring motor (increases reliability and durability especially under abuse, normally reserved for only the most costly high-end drivers)

Three Cabinets Too Many?

In reply to your thought, “DEBRA has about three cabinets too many!”, DEBRA subwoofers:

  • Are classic and only 1cf, with all corner edges rounded and finished in natural wood with low-gloss lacquer
  • Distribute easily throughout the room, against the walls, in enclosures only 10-3/8″ deep…only four visible panels per subwoofer and drivers face the walls
  • Offer a unique combination of performance and features available nowhere else

1kW Amp, Active Xo, Single-Band Parametric EQ

 

 

 

 

 

 

 

 

 

 

 

Introduction

Dr. Robert E. Greene is Senior Editor at The Absolute Sound Magazine and Math Professor at UCLA. He also tutored Russell Crowe in the violin for “Master And Commander” and the Appalachian accent for “A Beautiful Mind”. In TAS Issue 204, page 41, Dr. Greene wrote: “…in principal the multiple subwoofer concept, as realized in the Audio Kinesis (Duke LeJeune) Swarm system, should work better than the single sub that I was using-I hope to try that system later...”

DEBRA is the result of my personal search for affordable, state of the art bass in two successive sound rooms with horrific bass mode problems. In the first room I spent $750 for professional plans and several thousand dollars on professional acoustic treatments including a three-walled acoustic soffit with at best, mixed results.

Hearing is believing. The worse the room’s bass modes, the more DEBRA shines and the greater is its performance advantage. DEBRA has the “elastic” and musical qualities of bass in a commercial (large) space. Consider DEBRA your “last purchase” sub woofer for any music system or home theater system.

DEBRA employs four subwoofers each with a high-output reflex-loaded 10″ driver. Duke LeJeune of AudioKinesis specified the drivers, distributed array concept, and special “Room Gain Complementary” tuning. We specified original “Golden Ratio” siting instructions and cabinet architecture (cosmetics, fasteners, unique bracing, special laminate, and three panel materials to spread and distribute resonant qualities).

Two Rooms In One

By late 2008 I was convinced a properly designed distributed bass array defines state of art bass reproduction in any domestic space employed as a sound room. Conversely, regardless of cost or complexity, the performance of full-range single-column speakers is inherently flawed by design, varying tremendously depending on almost endless variables, all or most beyond the user’s control.

The reason is that a domestic room (a small space, as compared to a commercial size room such as a theater) affects sound waves differently above 150 Hz vs. below 150 Hz. We admit the audiophile “heresy” in the following statement: a domestic music system achieves the smoothest, most seamless, and most musical bass with a subwoofer system separate from the mid/treble speakers.

Domestic rooms have “modes” related to room dimensions causing serious time and frequency distortion in the bass range. In my current sound room deep powerful bass detracts from performance (except for this distributed bass array). Bass modes cause many audiophiles to prefer smaller speakers with less bass power and higher bass cutoff.

Professional reviewers often describe a laborious, time-consuming process of siting speakers for ideal, smoothest bass performance, then readjusting again for preferred mid/treble performance. The process repeats, presumably till attaining the best sonic compromise. The deeper and stronger the bass, the greater the modal effects and the greater the juggling process.

In October 2011 Jeff Hedback (Hd Acoustics) and Nyal Mellor (Acoustic Frontiers LLC) published Acoustical Measurement Standards For Stereo Listening Rooms. Hd Acoustics clients include Ozzy Osbourne, Lifehouse, and Trevor Horn. Page 19: “To obtain the best possible LF response…boundary interference issues can be tougher to address. Varying the fixed distances from ‘speaker to boundary’ and ‘listener to boundary’ will reduce strong cancellations. It is a balancing act as one location that may offer a smoother LF response may not provide the optimal midrange and treble response…” (emphasis added) Page 20, paragraph two: “…everyone desires a ‘flat’ LF response and no modal ringing. Simply, this is a tough achievement. The absurdly large collection of interrelated variables between two fullrange speakers and the room (speaker design, speaker/listener location, room size/construction and acoustical control within) makes this so. It is up to the individual to determine what their limits are as regards placement and acoustical treatments…” (some emphasis in original, some added…note the term “absurdly large”)

Listen carefully to music in a theater; the higher the system performance the better. Notice the “elastic” quality of the bass, perfectly integrating as one seamless whole with the mid and treble range, never drawing attention to itself.  Commercial spaces have modal effects, but the boundary dimensions and resulting wavelengths are so large that they occur below the audio range.

Conversely, bass from full range single column speakers in a domestic space often sounds disjointed from the mid/treble, as if the bass is in a different dimension.

After careful consideration you might agree the phenomena described above is the biggest difference between live music in a concert hall and reproduced sound in a domestic space. (Dynamic compression and reflected-vs.-direct energy are not-too-distant seconds.)

Remember the above is only a broad comparison of domestic rooms vs. sound reinforcement (commercial) systems.  DEBRA goes at least 1 octave lower and surpasses all performance specifications (except SPL) of any sound reinforcement system.

Once you become familiar with DEBRA’s performance advantage, the weakness of any full-range single-column speaker, regardless of cost or complexity, stands in stark relief.

All known setup comment for single-column speakers with true 20 Hz output discloses (usually indirectly) the flaw inherent in such design: the ideal locations for bass and mid/treble are mutually exclusive. This is an audiophile secret, the skeleton in our closet, the pink elephant in our media room implied but never confronted because of inherent flaws in prior solutions.

The distributed bass array is the new high-end audio standard. Single-column full-range high-end speakers will eventually disappear, a distant memory in audiophile history.

Alleged Modal “Cures”

Purpose-built commercial and domestic sound rooms have Golden Ratio relationships to minimize audibility of bass modes. The after-market’s so-called “cures” for bass modes include:

  1. Helmholtz resonators
  2. Acoustic absorbent such as fiberglass
  3. The ubiquitous digital electronic room equalization (“EQ”)

Resonators are too large and require a separate box for each band of frequencies. Absorbent is costly, takes almost endless quantities to absorb deep bass waves, and cause bass to sound overly dry (one maker/seller of absorbent room treatment simply instructs shoppers to purchase as much fiberglass as they can afford, meaning “more is better!”). Absorbent and Helmholtz resonators are unattractive and take up far more space than DEBRA. EQ causes multiple severe “hot spots”. It is difficult to impossible to boost the worst response dips with any of the above band-aid fixes.

The audio industry markets EQ as a panacea and most audiophiles perceive it as such. EQ is an elixir for audio marketers because it’s small, affordable, and reviewers and manufacturers publish attractive graphs displaying flat frequency response. Audiophiles believe in it because audiophiles are people and people are eternal optimists for the proverbial “free lunch”.

The problem with EQ is that it flattens frequency response in a static one-dimensional state, but modes exist in three dimensional space. Flattening FR in one location worsens response the same amount (or more) in another location. For a maximum of one listener whose head is locked in place, EQ has some theoretical potential, but even then, depending on the severity of a dip, it may require thousands of amplifier watts and commensurate speaker power handling, at incredible cost.

It’s more common now for digital EQ to sample and average the response at multiple room locations. This is hardly an “improvement” over one room location because it simply trades the advantage of one spot for less flat response at multiple locations.

The bottom line with EQ is it remains a zero sum game: rather than curing, solving, or eliminating the fixed mechanical problem of the room’s modes, even infinite EQ (impossible because of power constraints) can only “improve” the response at one location the same degree it detracts from performance at another location and/or locations.

Check this last item if you reply, “Me thinks thou does’t protest too much about EQ…”: Beyond EQ being a zero sum gain throughout the room (regarding FR), EQ does nothing to ameliorate the more audible problem of ringing/time smear. Bass notes associated with modal peaks continue to “ring” in the room after the bass player stopped and hit the next note.

Bass modes result from the room’s fixed, physical dimensions. It’s ideal to stop them from propagating in the first place rather than fix them after the fact.

Blazing A New Trail

Duke LeJeune of AudioKinesis, Dr. Earl Geddes, Dr. Floyd Toole, and Todd Welti blazed a different trail. In a nutshell, they specify three or four subs distributed throughout the room. Properly tuned and sited (my original instructions below), the subs act as new modes unequal to the room’s natural fixed modes. We reverse the polarity of one sub relative to the others to increase the unequal mode and smoothing effect (reversing two sub polarities subtracts first octave bass).

This bass philosophy promises all good things. The only risk is financial (admittedly not small for subs of this quality). The reward is the best bass you’ve ever heard, everywhere in your room, including the corners.

“Equalized” frequency response (FR) in the bass range throughout the room is impossible. EQ makes FR more erratic everywhere except the mic calibration site. Audiophiles generally desire a larger so-called listening “sweet spot”, yet EQ decreases the sweet spot to a sweet “dot”. Turn your head a few degrees and response may be worse after equalization. Let us know if you ever see a professional review publish response graphs outside the mic calibration site(s) before and after EQ is applied (we won’t hold our breath waiting for such to appear).

For the entirety of a domestic room bass modes can not be electronically “equalized”. Even though rooms are not air tight it’s reasonable to compare your room to a pressurized balloon. Pushing in the balloon at one spot deforms the balloon at another location. The pressure stays almost constant throughout the balloon. What EQ “fixes” at one spot in the room it makes worse at other spots.

Architecture vs. Quantity

I estimate well over 1000 published pages debating the relative merits and demerits of sealed, bandpass, bipole, dipole, ported, field coil, spaced dipole, corner-loaded, open baffle, and passive radiator systems for state-of-the-art bass reproduction. Add or delete servo-feedback control to any of the forgoing. Then there’s still electrostatic, planar, and ribbon technology (push-pull or single-ended for the last two). Want more? In the mid-2000’s Eminent Technology released an electric-motor fan (rotary) subwoofer that requires an amp capable of driving 1 Hz loads! A vocal proponent of one particular architecture might have several letters of science after his name with an argument supported by graphs, diagrams, and formulas. Very convincing indeed.

Thankfully, and what a relief, Dr. Earl Geddes put this debate to bed by thoroughly documenting that regardless of bass system architecture, a bass waveform reflects between two boundaries before one complete cycle is audible. In sequence, first the boundary makes its indelible imprint on the bass waveform, then the listeners perceive the waveform. For this reason and in this way, the boundary effects are more significant than differences between various sub architectures (presuming the subs are appropriately tuned).

Dr. Geddes proved the sub architecture is less critical than a minimum quantity of three subs, necessary to minimize the above described impact of the room’s boundaries. (Distributed sub arrays have one special tuning requirement unique to their architecture.)

Bass Quality Myths

Let’s suppose we are concerned only with well-built and properly tuned bass systems of all types (sealed, reflex, etc.), wired properly and driven by an amp with power reserve and adequate damping factor.  Listeners normally blame perceived qualities such as “quick”, “slow”, or “boomy” on woofer size, system type,  tuning specifications, or combinations thereof.  Such perceptions result from physical relationships between the location of the speakers, the listener, and the room’s boundaries.

For instance, perception could change from “boomy and muddy” to “lean” by changing position of the listener, the speakers, or both.

Ancillary Benefits

Separating a system into two component parts provides several other noteworthy benefits. The bass range has its own dedicated amplifier and likewise the mid/treble range.

Large, heavy, sub drivers capable of solid 20 Hz output require maximum current and voltage at long wavelengths, properties quite different from mid/treble requirements. Bass amp requirements lend themselves to lighter, smaller, lower cost, cooler-running, highest efficiency Class D architecture. Conversely, the mid/treble amplifier requires maximum resolution of shorter wavelengths, without concern for bass performance.

There is a much wider selection of speakers with limited bass output. Stand-mount monitors minimize cost and space, integrate easier into a living space, and boast better imaging and sound-stage potential. Floor-standing speakers have larger panels more prone to resonate. 20-Hz drivers sharing the same enclosure with mid/treble drivers requires Herculean mass and damping otherwise unnecessary with separate subs (some preferred single-column speakers weigh over 400 lbs each).

Single-column speakers capable of 20 Hz are large. The longer the internal dimension the lower the resonant frequency and the more likely it is to fall within the woofer bandpass. It’s possible to work around these problems…and always costly. And still, regardless of architecture, engineering and ultimate cost, no single-column speaker has DEBRA’s wide-bandwidth mode cancelling effect. (Costly, huge, floor-to-ceiling towers filled with multiple woofers cancel the dominant ceiling mode. But DEBRA mechanically equalizes all modes including the ceiling, for lower cost and with less environmental impact.)

Our original siting instructions below requires no physical trial and error for ideal bass performance in any room. All testing to insure the subs fit around fixed furniture and room openings can be done on paper.

The only physical trial and error testing is to discover which sub polarity to reverse (again, accomplished in under 30 minutes with our original instructions below). The overall setup process takes less time and effort than the never-ending trial and error associated with full-range speaker siting. Professional reviewers sometimes modify speaker setup even after a principal from the manufacturer spends hours at the same task.

Also, DEBRA allows for mutually exclusive ideal siting of the subs and main speakers, something impossible with all single-column full-range speakers.

Every difference between Debra and even the most complex cost-no-object full-range single-column speaker favors the former over the latter.

Why Not 20 Hz? Lower than 20Hz?

For listeners whose goal is highest performance, we wonder why anyone should settle for less than 20 Hz performance when considering a state of the art reproduction system. Further, we wonder why someone would consider something state of the art that does not employ a technique nature offers (dilution of the room’s bass modes) as the first choice to solve vexing bass mode issues.

Some fanatics may desire a cutoff below 20 Hz, and we sympathize with lofty performance goals. But keep the following in mind. For sealed systems driver excursion squares for each lower octave. For reflex systems such as DEBRA the following applies: Reflex tuning damps driver excursion at the port tuning frequency. The lower the bass cutoff the lower is port tuning and the lower is the frequency at which the driver is damped.

Compare a system tuned for an f3 of 16 Hz vs. 20 Hz: the 16 Hz system of course makes power 2/5ths octave lower than the 20 Hz system (for the rare recording with 16 Hz present and rare systems capable of reproducing it). But note that at higher mid-bass frequencies the 20 Hz system is closer to the port tuning frequency and hence its driver is damped more than the 16 Hz system. In the mid bass the 20 Hz system will likely distort less and have greater power handling than the 16 Hz system. The human ear may not be sensitive to the difference in distortion, but the 20 Hz system has a larger and safer power envelope than the 16 Hz system at higher mid bass frequencies.

How many 16 Hz pipe organ and synthesizer recordings do you have?

Home Theater Performance

We have a unique dual use system for both music reproduction and home theater. It employs a pure analog Trinaural Processor for music (described on another page at this website). For video there is a 1080P front projector and 92″ retractable perforated screen about 7′ from the front wall. Spaced well out from the front wall are six main front monitors, two monitors per each identical channel in our original “I-RAA” (inverted Romeyn Ambiance Array).

DEBRA provides sub duty for both music and HT. This audio system provides previously unheard HT performance, especially spatial qualities (imaging, stage depth, stage intensity, etc.).

In over two years of use, reproducing every HT audio effect in the bass range, I’ve reached for the volume control to save my ears and maintain some semblance of domestic tranquility, but never exceeded the bass system’s output capacity.

“Room Gain Complementary” (RGC, Duke LeJeune) Tuning

Duke LeJeune of AudioKinesis coined the term Room Gain Complementary (RGC) tuning, described HERE. Duke’s “Dream Maker” bipolar speaker won The Absolute Sound’s 2008 Golden Ear Award. Duke also designed and manufactures what independent musicians agree is the best compact speaker cabinet for electric bass and all acoustic instruments, the AudioKinesis Thunderchild (see the 51+ page AudioKinesis 112 thread w/ 1000 posts + Part Two ).

Duke added excellent gilding to the multiple subwoofer lily. Beyond modal effects, domestic rooms boost the bass an average of +3 dB per octave below 100 Hz (+7 dB @ 20 Hz). Comparing sealed tuning vs. standard reflex tuning, the former more closely mimics Duke’s RGC tuning than the latter. We believe this explains why many audiophiles prefer sealed tuning over reflex. (When, by pure coincidence, the port of a reflex system is tuned to a room’s modal peak, the result is grotesque one-note bass. This is another reason why audiophiles sometimes prefer sealed over reflex. We know of no inherent advantage in any system architecture as long as it is tuned properly.)

Stereophile Magazine well describes this effect in their 2009 review of Harbeth’s superb 40.1 monitor. It’s flat anechoic deep bass response is better suited for larger rooms, whose modal effects are lower in frequency than smaller rooms. (I loved the Harbeth 40.1 at 2008 T.H.E. Show.)

No Proximity Effect

Bass is so non-localized (no proximity effect) that the subs are completely invisible as a sound source beyond a few mere inches. You’ll have to touch the driver or the enclosure to confirm it is active.

Summary

To summarize, the room’s modes cause irregular bass response. In effect, each of the multiple subs dilute the room’s modes, resulting in flatter response at all points in the room.

DEBRA’s small subs and the ease with which they integrate into a domestic space make DEBRA the ideal bass solution.

Herculean power, RGC tuning, and natural mode-flattening effects leave nothing to be desired in state of the art subwoofer performance.

Walk around a room employing standard sub technology or single-column speakers with deep, powerful bass. Whether or not EQ is employed, the modes in domestic rooms result in big response swings at different locations. In spite of my room’s otherwise horrific bass modes, DEBRA sounds linear and natural throughout the room, even in all four extreme corners.

Comparing One Sub vs. Four

My regular demonstration technique is to play a good jazz acoustic bass at moderate level. I disconnect three subs, leaving only one sub playing, and increase sub amp gain 4.5 dB (would be 6 dB except that one sub polarity is inverted). Listeners immediately notice:

  1. The double bass looses about half its sound quality
  2. The sound stage collapses and intensity decreases…instead of the music energizing the entire room it is focused only in the front
  3. Bass FR is rougher and some notes disappear…transient leading edges are dulled…the musician omits certain notes and follows the beat with less accuracy

The difference is not subtle.

Enclosure

In 2008 I discovered a new tw0-layer laminate for speaker panel use (the top plywood layer is visible on the corner edges). We changed from the Baltic Birch plywood shown in the images to a new improved cross-grain plywood with even better damping qualities. Sound tests proved the laminate’s superiority over either material by itself. I chose 5/8” of each material for 1-1/4” total thickness for the sides, top, base, and front. The driver baffle is three layers, 1-3/8″ thick, and a material different from the laminate materials.

After the fact, I discovered a celebrated, award-winning designer employed a mixture of panel materials similar to DEBRA.

Each DEBRA enclosure employs three panel materials to spread and dilute panel resonance (two materials per panel except the baffle is three-layer/single material). Notice the recurring theme of mode and resonance dilution, from product inception to our original Golden Ratio siting instructions found elsewhere on this page.

The largest panel is only 10″ x 24″. Each panel is individually laminated and glued with several clamps. Each clamp’s pressure is widely and evenly distributed through solid 2″ x 2″ maple blocks. Gluing large sheets, then cutting to size would save time and money, but the extra effort is worth the performance gain and long-term service.

The finish is low-gloss. The driver baffle is finished a fine-texture charcoal grey. The baffle is raised 1/16″ with a crisp beveled edge corner accent.

The drivers fasten with black M6 hardened steel machine screws and special inserts for beauty, performance, and reliability.

A special and unique bracing system interlocks the face, the driver, and the baffle to further minimize system resonance and maintain constant torque on the driver and its six fasteners.

DEBRA Setup Instructions, copyright James Romeyn

Contact us for easy in-wall setup instructions.

Read all setup instructions before starting.

Insure cone supports stay clear of all wire and cable.

The reference point for siting each subwoofer is the lateral mid-point between the port flare and 10″ driver, marked with a small down-pointing arrow carved in the face just above the base.

Some rooms lack intersect points for two walls where such point would otherwise mark one of four outermost corners of a four cornered room. Consider such points as one of the four corners specified below.

All four subs site with the driver baffle facing the wall, about 1-3/8″ distance from wall to the driver baffle, for a clean uncluttered appearance.

Label each of four subs A through D. Later we assign each sub to a specific wall and a specific distance from the closest corner. There are multiple wall/corner choices to fit the subs around room openings and fixed furniture, explained below.

The sub spacing (to its associated corner) ascends alphabetically: Sub A is spaced X from its related corner, Sub B is greater than A, Sub C is greater than B, Sub D is greater than C.

Screw a threaded stud into each speaker support cone. Screw three speaker support cones into each subwoofer.

“Smoothest Bass” Site For One Sub

The purpose of this test is to confirm suitable locations near the wall producing the smoothest, most linear bass for one subwoofer. This test mimics or “mirrors” the boundary, subwoofer, and listening seat relationships during normal listening with one subwoofer. The subsequent locations for the remaining three subs are mathematically related to the location of this first subwoofer. Thanks to Bob Carver for this general advice.

This procedure employs:

  1. One 4-post sub
  2. One 2-post sub
  3. Speaker wire from sub amp to the site of the main listening seat
  4. About 4-5’ speaker wire interconnects the above two subs next to each other

Connect the speaker wires per text on the sub terminal boards.

If the floor is finished wood (even if carpeted over), use the included flat discs under the flat speaker cones. If there is carpet over unfinished sub-floor, screw the points into the speaker support cones.

Clear the space normally occupied by the main listening seat. Place the two subs normally, port firing down, centered under the site where would normally be the head of the main listener (the “sweet spot”). To maximize dispersion orient the two subs at 90-degree angle and about 5mm from each other.

Look around the room with all furnishings placed normally (except the aforementioned listening seat). Note all locations where a sub will fit near and facing the walls. Temporarily clear furnishings from the vicinity of these potential sub locations. Your body will occupy these spaces momentarily during the following test.

Play music program with electric or upright bass through the two subs at the listening seat. Stand 3-4′ from a wall. Bend at the waist, your head horizontal facing the floor, stopping when your ears reach ear level in the main listening seat. Between the wall and the top of your head should be 2″-3”.

Place “Post-It” notes at 3 to 4 locations near the walls where one sub could be placed, providing the smoothest, most linear, ring-free bass response. Overall bass gain may be lower at these locations. Take your time with this process. Double-check the results. This is the most tedious process of the instructions. Label the “Post-It” Notes “SB1,” “SB2,” etc, in descending order of smoothness (SB1 = smoothest bass site).

The marked sites produce the smoothest bass for a listener at the primary seat, employing one subwoofer.

This test is complete. Remove the two subs and replace the main listening chair.

Siting The Remaining Three Subs

Diagram the floor plan, furnishings, and room openings with graph paper or design program.

Measure the distance from SB1 to the nearest room corner.

Center one sub on the floor at point SB1.

Golden Ratio (1.618) determines the ideal distance from room corners to the three remaining subs. Wikipedia states: “The golden ratio has the simplest expression (and slowest convergence) as a continued fraction expansion of any irrational number.” “Slowest convergence” results in maximum null effect because the three remaining subs are least likely to stimulate the same modes as SB1.

We maximize potential for the subs to act as four new random modes, unequal to the room’s fixed modes, thereby maximizing potential for the smoothest and most linear bass throughout the entire space of the listening room.

Only the sub assigned to SB1 has a specific wall and corner reference point. All three remaining subs can site on any wall referenced to any corner.

The Three Remaining Subs

Multiply or divide SB1 by the GR decimal to determine the next sub-to-corner spacing. From conversations with Duke LeJeune and our own experiments we suggest a minimum spacing of 15”.

Each subsequent remaining sub location = the prior spacing (from nearest corner to sub) divided or multiplied by Golden Ratio.

Example I

SB1 = 30”. The second sub sites <30” from its related corner. The third and forth subs site >30” from their related corners:

Sub A: 30”/1.618 = 18.54” from any corner on any wall

Sub B: SB1 = 30” from specific corner on specific wall (see instructions)

Sub C: 30” x 1.618 = 48.54” from any corner on any wall

Sub D: 48.54” x 1.618 = 78.54” from any corner on any wall

Example II

SB1 = 30”. All three remaining subs site more than 30” from their related corners:

Sub A: SB1 = 30” from specific corner on specific wall (see instructions)

Sub B: 30” x 1.618 = 48.54” from any corner on any wall

Sub C: 48.54” x 1.618 = 78.54” from any corner on any wall

Sub D: 78.54” x 1.618 = 127.08” from any corner on any wall

Notes

To fit subs around furnishings and wall openings swap corner or wall assignment for subs other than SB1. This provides huge flexibility in placement. If still no appropriate option appears, substitute SB2 for SB1 and recalculate all subsequent locations as per above. If still necessary, substitute SB3 for SB2, etc.

The sub’s proximity to walls, minimum enclosure depth, and multiple wall/corner/SB options accommodates any room, furnishings, and openings.

Sub Amp Phase Control

Set this rotary control knob at 12:00 (90-degrees phase) for maximum expansion of the sound room’s boundaries, thus minimizing their modal effects.  The final stage, inverting the polarity of one sub, further minimizes mode effects.

Invert Polarity of One Sub

This process starts (and ends) with three subs in normal polarity and one sub in inverted polarity. Your job is to find the ideal sub to invert.

For this test, the more audible are the bass modes stimulated by the music, the easier and more efficient is the process. In other words, ideal music for this test stimulates particularly loud, nasty, obvious, and obnoxious bass mode(s).

To invert a 2-post sub, access the binding posts on its linked 4-Post sub. Invert only the nickel “SUB” binding posts.

To invert a 4-post sub, access its binding posts. Invert its nickel “SUB” posts and its gold ”AMP” posts.

Inverting the correct sub produces the smoothest overall bass. It is also likely to produce the lowest average loudness.

I can hear your protest all the way up at 4900 feet elevation in north Utah’s Rocky Mountains: “Since when is lower gain desirable?” In our philosophy, lower average gain results from the least exciting of bass modes, proving the theory in action with audible results.

“Louder” mode-excited bass is frequency sensitive. Louder notes exist only in a backdrop of notes attenuated or missing in action. Even worse and more damaging, louder notes distort the rhythm of the bass line, being the music’s very foundation. Again, this explains why audiophiles may prefer less bass power and/or a higher cutoff.

Plus bass gain in a domestic room with a normal audio system is location-sensitive: flattening the peaks at the sweet spot (with digital EQ) might produce repulsive effects at the room’s entryway.

DEBRA equalizes “average” bass power. While certain notes are “quieter,” other notes otherwise unheard are naturally raised to the average power level. But it shines even brighter by eliminating the awful and ubiquitous bass note ringing, and restoring correct bass note timing. Duke labeled this phenomena “Deconstructive Interference.”

By their very nature FR peaks and valleys caused by room modes are non-linear. DEBRA naturally prevents the modal effects from propagating in the first place rather than all other cures which are after-the-fact.

DEBRA has plenty of power reserve. Simply advance the sub amp gain control to compensate for the lower overall sensitivity associated with the flattened modes, AKA “Deconstructive Interference.”

If/when you are ready to be permanently spoiled, audition this subwoofer system with huge power @ 20 Hz and bass mode effects banished throughout the room. And look ma, no EQ and no bass traps!

Wiring

Insure cone supports stay clear of all wire and cable.

The sum total (100%) of the resistance of a speaker circuit = the series speaker wire resistance + the driver(s) resistance. The higher the driver resistance the lower is the speaker wire’s portion of 100%. The lower the wire’s portion of 100% the less the wire’s resistance degrades performance. Other variables exist, but for our purposes the higher the driver resistance the better. This explains why we chose the following series/parallel wiring scheme.

On each 4-post sub connect its nickel (“SUB”) posts to a 2-post sub and connect its gold (“AMP”) posts to one of the sub amp’s two pairs of output binding posts.

Follow correct polarity throughout except for the inverting process described elsewhere.

Measure the wire length from the sub amp to the 2-post sub flanking the L, then from the sub amp to the 2-post sub flanking the R (disregard the 4-post sub for this measurement). To calculate the minimum AWG input the wire length at this site: http://www.bcae1.com/images/swfs/speakerwireselectorassistant.swf . The sub amp makes 1kW total into 4 subs or 500W into 2 subs. Type “500” in the calculator cell for wattage.

Overall Results

DEBRA, with unique cabinet build, employs exceptional overall design and engineering throughout.

My sound room’s bass modes are so strong that a single sub with EQ can not successfully integrate; results were similarly unacceptable with two small subs under each L/R monitor after pivoting the four subs in every possible combination of directions. Three subs properly distributed throughout the room (one must be sited above ear level) was only marginally successful.

The overall presentation with this system’s unique features is remarkable by any standard. Response is smooth and linear with an “elastic” quality and musically natural integration similar to a commercial (large) space.

DEBRA’s mono bass signal has no audible disadvantage compared to stereo. In the range of bass fundamental tones, stereo bass is irrelevant, even more so compared to well documented modal effects (severe ringing/timing distortion, +/- 15 dB is not unheard of). Consider the following relationships: the room’s boundary dimensions, bass fundamental wavelengths, and the distance between two stereo full range loudspeakers. How likely is a listener to discern disparate L/R signals in the range of bass fundamental tones, presuming one has a recording with such tones?

DEBRA provides low distortion, uncanny pitch definition, 113 dB @ 20 Hz (conservative), and smooth, musical response throughout the room. Over the past thirty years or so I have carefully auditioned the best cost no object systems from stereo electrostatic to Kimber Iso-Mic 4-channel to Andrew Jones’ TAD 5-channel Reference One (the later two systems with proprietary master recording sources).

We believe DEBRA provides a new state of the art reference that will spoil you vs. inferior sub systems. It’s not inexpensive, but on the other hand you could spend a lot more for yesterday’s architecture, less musical performance, and far less flexibility.

Dayton SA1000 Sub Amp

30.8 lbs

Rear panel:

All audio inputs RCA unbalanced: L/R are summed mono, use both or either. One “LFE Direct” input bypasses Xo.

3-position rear panel slide switch for power: Trigger/Auto/On

Front panel power switch.

DEBRA recommended default settings for front panel continuous rotary controls:

Single Band Parametric EQ: If the parametric is used it is only to shape or tilt one octave upward or downward. For such application set “CUE” fully clockwise to “1.0” (one full octave width). Avoid narrow “CUE” tuning (“0.1″ = one tenth octave width). Such EQ is unnecessary and does not benefit DEBRA.

Phase: see setup instructions

Freq: (crossover) depends on main speaker bass cutoff and power. Several benefits accrue with an active high-pass crossover on the main speakers. We employ the active high-pass crossover in a Trinaural Processor (in-phase 2nd-order @ 80 Hz). Crossover up to 100 Hz permissible. Look for our future article describing an effective ambiance array and mode-flattening technique for stand-mount monitors.

Gain: to taste

Name Brand Competition

JL Audio’s Gotham g213 is certainly among the best name brand sub systems. It’s static specifications and premium build and finish quality properly reflect its stratopheric $12k cost.

Audiophiles sometimes prefer sealed bass systems like Gotham because they have no port. When a port tuning frequency happens to overlap one of the room’s many bass modes (frequently the case) the result is extreme bloat and overhang. Also, a sealed system’s slower roll-off rate mimics the effect of DEBRA’s RGC tuning. Finally, sealed systems generally have more linear transient performance.

But DEBRA has every advantage over a sealed system, even one as princely as Gotham. Reflex systems require multiples less power and cone travel (displacement) for similar power at the lowest frequencies (the cone of a reflex system is maximally damped/almost stationary at the port tuning frequency). The human ear has extremely low sensitivity to a reflex system’s transient distortion: harmonic distortion up to about 30% in the bass range is almost inaudible to humans, consistent with Dr. Earl Geddes’ conclusion re. architecture vs. quantity described elsewhere on this page. The tolerance for bass distortion does not extend to modal effects, which cause grotesque FR swings and distort timing, notes ringing long after they should have stopped. Note: maximum sensitivity to phase and harmonic distortion is in the mid-range, enabling a blindfolded person to accurately picture the arc of a coin turning on its edge, or the location and trajectory of a nearby predator.

DEBRA fulfills the loftiest audiophile goals for “quality” of bass reproduction at every physical location in any domestic listening space. DEBRA meets the classic 20 Hz cutoff goal and has acoustic power for HT applications.

Every fine, lasting, enviable structure starts with the strongest possible foundation. Every band and orchestra plays no better and no faster than its foundation, the bass. DEBRA is a fine, permanent foundation on which to build a lifetime of audiophile dreams. It cost more than the average sub system, yet compares admirably to products costing many multiples greater.

DEBRA offers original thinking and an ideal, novel approach to deliver state of the art bass for both music and home theater in a compact, attractive, affordable, and easily placed package.

Happy listening!