DEBRA

Distributed-EQ Bass Reflex Array, 5+ pieces

$2990 USD + Shipping, Extra Cost For Custom Finish

No comparable commercial system, a unique solution from nature: the room’s preexisting fixed modes + four new “Golden Ratio” bass modules = 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 with power to spare for knockout HT punch.

• Four reflex bass modules 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 ship within 90 calendar days

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Frequency Response: 20 – 160 Hz (-3 dB)

Total System Weight: 300 lbs (amp, spikes/flats, four bass modules)

Four High Output 10″ drivers, 2400Wrms total power handling

Sensitivity 91.5 dB/W/M @ 4-Ohms, one sub polarity inverted

Unique qualities of bass reproduced in a commercial (large) space

Each bass module 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 + natural acoustic mode-canceling effect (no absorption/no resonators/no automated EQ) for the flattest, most natural bass throughout the listening room including corners

Support cones + floor discs, three per sub, precision machined solid brass, durable black chrome finish, 86 grams each, 2-pieces terminate flat or spiked, 1-1/4″ diameter x 1-1/2″ tall (spiked, flats slightly shorter)

 

Four 10″ drivers, each:

17.1 lbs

600Wrms

Magnet 100 oz.

Xmax 12.3 mm

Voice coil 2.5″ 4-layer

Anodized aluminum cone

Vented, triple shorting ring motor

Three Cabinets Too Many?

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

• 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 bass module and drivers face the walls
• Offer a unique combination of performance features available in no commercial system

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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.  This can rightly be considered a “last purchase” bass reproduction system for any music and/or home theater system.

DEBRA employs four bass modules each with a high-output reflex-loaded 10″ driver.  Duke LeJeune of AudioKinesis in Preston, ID specified the drivers, distributed array concept, and enclosure tuning including Room Gain Complementary effect.  We specified special driver fasteners, cabinet cosmetics and construction, original “Golden Ratio” siting instructions, and enclosure materials including the panel laminate.

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 200 Hz vs. below 200 Hz.  In effect, the domestic sound room is two rooms in one.  It follows that the ideal domestic audio system should be similarly split into two functions.

Domestic rooms have “modes” related to room dimensions causing irregularities in bass performance. In my current room the response dips and peaks below 200 Hz are so audible that it is preferred without deep bass except for this distributed bass array.  Bass modes cause many audiophiles to prefer smaller speakers with higher bass cutoff and with little bass power.

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, resulting from larger boundary spacing vs. a domestic space.  Conversely, bass in a domestic space reproduced with full range single column speakers sounds “mechanical” and a-musical, separate and disjointed from the mid/treble, as if it occurs in a different dimension (manufacturers like Audio Note and others minimize this effect by specifying corner-loading, trading one set of problems for others).  After careful consideration you might agree the phenomena described above is the biggest difference between  music in a concert hall and reproduced sound in a domestic space.  (Dynamic compression and reflected-vs.-direct energy are not-too-distant seconds.)

DEBRA performs in a domestic space similar to bass in a commercial space such as a theater.  (Note: DEBRA also goes at least 1 octave lower than commercial theater systems.)  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, till now.

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 free lunch.

The problem with EQ is that it flattens frequency response in a static one-dimensional state, but modes exist in the room’s three dimensions.  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.

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 in Idaho, Dr. Earl Geddes, and Todd Welti blazed a different trail. In a nutshell, they specify three or four subs distributed throughout the room.  Properly tuned and sited (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).  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.)

Crossover >100 Hz Ideal

It is almost universal audiophile wisdom to cross subwoofers as low as possible, sometimes as low as 30-40 Hz.  But bass mode effects occur up to about 200 Hz.  We call DEBRA’s enclosures “bass modules” because their FR extends well above 100 Hz.  The higher DEBRA is crossed, the more modes it flattens at elevated frequencies.  We offer an optional line-level high-pass crossover for the main speakers to minimize overlap, increase dynamic envelope, and decrease stress on the main amp and speakers.

Ancillary Benefits

Separating a system into two component parts (below and above about 150 Hz) 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 generally have better imaging and sound-stage performance.  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…but also 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 ceiling bounce, usually the dominant mode.  But DEBRA mechanically equalizes all modes including ceiling bounce, 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).  On whole, this is far less time and effort than the never-ending trial and error associated with full-range speaker siting, unless one is lucky enough to have Peter McGrath setup and tune their system.

Compare the above to siting any full range speaker flat to 20 Hz.  Even professional reviewers almost invariably modify speaker siting after the speaker designer spends hours of laborious setup time!

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

DEBRA advantages outweigh any single-column full-range system regardless of cost or complexity. Every difference between a full-range single-column speaker and split system with distributed bass array favors the latter over the former.

Why Not 20 Hz?

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.

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.

“Room Gain Complementary” (RGC) 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 every single independent source agrees is the best compact speaker cabinet for electric bass, acoustic bass, cello, jazz guitar, and acoustic guitar, 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 the +/- F.R. swings caused by modes, domestic rooms boost the bass an average of +3 dB per octave below 100 Hz (+3 dB @ 50 Hz, +6 dB @ 25 Hz, +7 dB @ 20 Hz).

Stereophile Magazine well describes this effect in their 2009 review of Harbeth’s superb 40.1 monitor.  The 40.1 has flat anechoic deep bass response and is better suited for larger rooms because their modal problems are lower in frequency and less often excited.  (I loved the Harbeth 40.1 at 2008 T.H.E. Show.)

Duke designed DEBRA with RGC tuning, rolling off at 3 dB/octave below 100 Hz.  A single-band parametric EQ can not mimic the effect of RGC tuning because its one-octave bandwidth is too narrow.

RGC tuning combined with the mode-flattening effect and Herculean power (conservatively rated 113 dB @ 20 Hz) is exactly what you should expect in state of the art bass reproduction.

Walk around a room employing standard sub technology or full-range single-column speaker with deep 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.

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 compensate for reduced sensitivity by increasing the sub amp gain 4.5 dB (would be 6 dB except that one sub polarity is inverted).  Listeners immediately notice:

1. It sounds like the quality of the double bass is half of the quality while DEBRA was employed
2. The sound stage collapses and thins out…instead of the music energizing the entire room only a small portion of the front of the room is energized
3. Erratic bass FR, like the player omits certain notes, and other notes sound loose and non-distinct, lasting longer than before.

The difference is not subtle.

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…even crossed above 100 Hz and even with peaks above 100 dB.  You’ll have to touch the driver or the enclosure to confirm it is active.

Enclosure

In 2008 I discovered a new tw0-layer laminate for speaker panel use (the top plywood layer is visible on the corner edges).  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 employs in his current speakers the same panel materials as 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 painted low-gloss black/gray for a textured appearance.   The baffle is raised 1/16″ with a crisp beveled edge corner accent.

The drivers fasten with 6mm black alloy hex head machine screws and solid brass wood inserts for reliability, cosmetic effect, and audio performance.

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 bass module is the lateral mid-point between the port flare and 10″ driver, marked with a small black down-pointing arrow on 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 distance (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.

Locate Position For Sub “SB1”

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.  Invert the two subs for normal operation, port firing down, centered under the site of the main listener’s head during normal listening (the “sweet spot”).  Orient the two subs at 90-degree angle one to the other to maximize room fill.  Space the two closest sub panels 1-5 mm.

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 while listening in your favorite seat.  Space 2-3” between the wall and the top of your head.

Place a “Post-It” Note at 3-4 different points on the walls where bass is the smoothest and most linear.  Bass gain may be lower at these locations.  Take your time with this process.  Double-check the results.  A big payoff comes soon.  Label the “Post-It” Notes “SB1,” “SB2,” etc, in descending order of smoothness (SB1 = smoothest bass site).

The above test mimics the boundary, subwoofer, and listening seat relationships during normal listening.  (Thanks to Bob Carver for this advice.)  The marked sites produce the smoothest bass for a listener at the primary seat.

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 directly below 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.”  The Golden Ratio “slowest convergence” insures the three remaining sub-to-corner distances are least likely to be even multiples of the SB1-to-nearest corner distance.  The GR insures the remaining three subs are least likely to multiply any modal effect resulting from the first sub located at point SB1.  Further, SB1 produced the smoothest and most linear bass at the listening seat.

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

Wall/Corner Priority

To the extent allowed by the wall’s length and the room’s openings and furnishings, site a total of two subs on the wall defined by SB1.  Up to three subs may share the same wall as SB1.

Similar to above, to the extent allowed by the wall’s length and the room’s openings and furnishings, site two subs referencing the same corner as SB1.  Up to three subs may reference the same corner as SB1.

The two instructions above maximize the GR/unequal mode effects described earlier.  Neither instruction is mandatory.

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, following the priority above.

The Formula

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 sub-to-corner distances 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”.  One sub sites <30” from its related corner, the two remaining subs site >30” from their related corners:

Sub A: 30”/1.618 = 18.54” from any corner on any wall, see “Wall/Corner Priority”

Sub B: SB1 = 30” from specific corner on specific wall

Sub C: 30” x 1.618 + 48.54” from any corner on any wall, see “Wall/Corner Priority”

Sub D:  48.54” x 1.618 = 78.54” from any corner on any wall, see “Wall/Corner Priority”

Example II

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

Sub A: SB1 = 30” from specific corner on specific wall

Sub B: 30” x 1.618 = 48.54” from any corner on any wall, see “Wall/Corner Priority”

Sub C: 48.54” x 1.618 = 78.54” from any corner on any wall, see “Wall/Corner Priority”

Sub D:  78.54” x 1.618 = 127.08” from any corner on any wall, see “Wall/Corner Priority”

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.

Remember, if practical, site at least two subs on the wall defined by SB1 and reference two subs to the SB1 corner (see Wall/Corner Priority).

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.

The more audible are the bass modes stimulated by music used in this test, the easier and more efficient is the process.  In other words, ideal music for this process stimulates particularly loud, nasty, obvious, and obnoxious bass mode or modes.  Normally, such modes increase SPL and distort the time value of the bass note: the notes last longer than their original time value in the music notation.  Beyond that, consider powerful, well recorded, wide-range acoustic jazz upright bass such as John Pizzarelli, Rockin’ In Rhythm, A Tribute To Duke Ellington, Telarc TEL-31921-02.

Inverting the correct module 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: “Why would you want to tune/setup a reproduction system for minimum average bass gain?”  Because, in this case, minimum bass gain is consistent with the least exciting of bass modes, proving the theory in action with audible results.

“Louder” mode-excited bass is selective.  Louder notes exist only at the expense of other notes attenuated or missing in action.  Even worse and more damaging, louder notes ring, destroying the timing of the bass line, being the music’s very  foundation.  Again, this justifies many audiophile preferences to forgo deep bass altogether.  Musicians know the orchestra can play no faster than the bass musicians can play.

Plus bass gain in a normal audio system is non-linear vs. location: flattening the peaks at the sweet spot (with digital EQ) can easily produce physically repulsive modal 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 the 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.”

Sub Amp Phase Control

Adjust this control after selecting the inverted sub.

Locate the continuous phase control on the sub amp.  This procedure is easiest performed with an assistant at the sub amp while someone else listens at the primary seat.  The assistant selects phase control settings while the listener judges bass integration and bass transients with the rest of the music.  Rather than be a hard, long, drawn out session we believe the listener will easily discern a preferred setting.

The assistant at the amp selects the following phase control settings while the listener judges:

1. 0 degrees or 180-degrees. If listener prefers 0-degrees see #2, if 180-degrees skip to #5.
   
2. 0 or 90-degrees. If listener prefers 0 see #3, if 90 skip to #4.
   
3. 0 or 45-degrees. Stop at listener choice, you’re done with the phase control.
   
4. 45, 90, or 135-degrees.  Stop at listener choice, you’re done with the phase control.
5. 180 or 90-degrees.  If listener prefers 180 see #6, if 90 see #4.
   
6. 180 or 135-degrees.  Stop at listener choice, you’re done with the phase control.
   

Wiring

Insure cone supports stay clear of all wire and cable.

The sum total (100%) of the series resistance of a speaker circuit = the series resistance of the speaker wire + the resistance of the drivers.  The higher the driver impedance 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 module connect the gold (“AMP”) posts to the amp and connect the nickel (“Module”) posts to a 2-post module.  Follow correct polarity throughout except for the inverting process described elsewhere on this page.  Each 4-post modules has a dedicated pair of binding posts (4 total) on the back of the sub amp.

Each 4-post module (4-Ohms) series-connects to a 2-post module (4-Ohms) for 8-Ohms (subtotal).  The two 8-Ohm circuits in parallel at the amp equals 4-Ohms total.

Input wire length for each subwoofer pair here http://www.bcae1.com/images/swfs/speakerwireselectorassistant.swf to calculate minimum AWG.  Type “500″ in the calculator cell for wattage (sub amp total 1kW/2 sets of two subs per twin-lead wire length).

High-Pass Crossover for Main Speakers

For $200 extra cost, included is a simple stereo 6″ interconnect terminated with RCA plug and inline RCA jacks or balanced XLR terminations, with in-line series Wima capacitor to high-pass cross the main speakers in a line-level connection.

Overall Results

DEBRA, with unique hand-crafted architecture of the bass modules, 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 modules 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.  The modules and mains cross higher than 100 Hz without directional cue, resulting in less stress, lower distortion, and huge dynamic envelope for the main speakers.

Commercial (large) spaces have bass modes, but the room’s dimensions are so long that the modes are infra-sonic and hence inaudible.  This explains why bass sounds better in a commercial space than in a domestic space (when DEBRA is not employed).  But pro-sound reinforcement in commercial systems rarely dips below the mid-40 Hz range.  DEBRA extends to 20 Hz for more than one octave greater extension than sound reinforcement systems, but with the smooth musical pleasure of bass in a commercial space.

DEBRA’s mono bass signal has no audible disadvantage even crossed above 100 Hz.  Compared to the often horrific, well documented effects of bass modes in domestic spaces (+/- 15 dB is not unheard of), stereo effect in the bass range is irrelevant.  In fact, disparate bass signals would only decrease the null effect and result in lumpier bass.  The main speakers carrying bass overtones are still discreet with no signal blending whatsoever.

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 (the two later 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, flat settings: Freq. 80 Hz, Bandwidth 1.0, Gain 0 dB.  Not recommended for narrow bandwidth tuning…rather leave flat except to tilt/shape entire bandwidth for flattest overall response.

Phase: see setup instructions

Freq: (crossover) to taste

Gain: to taste (see instructions)

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.  FYI: 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!