[Duke]

The purpose of this poll is to help me gauge interest in a new product that I haven't decided whether or not to go into production with.  Also, this is a sneaky way for me to promote my product under the guise of a poll.  As if you hadn't figured that out already.

So here's the deal:  If the interest is there, I'm in a position to launch the newest member of the Planetarium line, the Gamma.  And if it's not, well... I'd much rather find out now than later!

In honor of these relatively lean times, the Gamma system will be considerably less expensive than Planetariums Alpha and Beta.   My target introductory price is three grand.  That would be for a pair of satellites that are designed with a high priority on radiation pattern control, plus a four-piece sealed Swarm version 3.0.   

Preliminary specs for the satellite system:

Type:  Stand-mount, controlled-pattern, vented box
Efficiency:  93 dB/ 1 watt/ 1 meter (calculated from Thiele/Small parameters)
Nominal impedance:  8 ohms, minimum 7 ohms
Bandwidth:  80 Hz to 18 kHz
Thermal compression:  Less than 1 dB at 106 dB SPL
Recommended amplifier power:  5 to 100 watts
Dimensions:  18" H x 10" W x 12" D
Weight: 40 pounds each

Preliminary specs for subwoofer system:

Type:  Four-piece sealed-box Swarm
System Qtc:  .5 (point five)
Bottom-end extension:  To 28 Hz in-room with 80 Hz crossover; to 23 Hz in-room with 35 Hz crossover
Thermal compression:  Less than 1 dB at 106 dB SPL
Mechanical:  Subs will not exceed X-max will full power input down to 20 Hz
Low-pass filter:  Continuously variable, 30 Hz to 180 Hz, 4th order
Other features:  0 to 180 degree continuously-variable phase control, single band parametric EQ
Amplifier power:  1000 watts (one shelf-mount amp drives all four subs)
Warning:  The amp only has line-level inputs; speaker-level adaptor available for $70 from Audio Magus
Dimensions of subs:  15" H x 14" W x 14" D; 45 pounds each
Dimensions of amp:  19" W x 4" H x 14" D; 32 pounds

If you don't mind, please participate in the poll so that I can get an idea of the level of serious interest the Gamma system can realistically hope to generate.  I'm in a position to go into small-scale production with it, but if there's realistically little or no prospect of making actual sales at this time then I may hold off until times are better.

Thank you.

Duke

[cryoparts]

Cool.  Bump to the top for Duke.

Hey, no one called you a bum yet!   

Peace,

Lee

[Duke]

Thanks, Lee!

So far "bum" is still tied for last place in the polling.  That's a good thing, right?  Or, does it just mean not many people have found this thread yet??

[Russell Dawkins]

I just saw it now, but I haven't been on AC so much recently. I've been busy.

I think you're heading in the right direction with this, Duke. This should smoke most of the competition at that price, once the swarm is factored in, and I presume it would employ a waveguide/horn which is, I think, a very practical configuration for the typical sub-perfect listening environment.

Personally, and I know I am not typical in this, a sticking point would be the mono swarm, given the 80Hz crossover. I would prefer stereo. I just did a comparo of some speakers with a 90Hz crossover and a mono sub - albeit a single sub - with a foot pedal control by which I could simultaneously punch the sub out and send the full range signal to the satellites. The tone and blend was great but since I listen to orchestra a lot I instantly missed the stereo bass. The basses and the tymps moved audibly towards centre.

It was a trial and I took it back without a second thought. I will replace it with 4 H frame subs, a stereo amp and a Behringer DCX 2496.

[Duke]

Thanks, Russell!

A stereo version of the Swarm would simply require purchasing an additional amplifier.  So there would be some additional expense, but not a whole lot.

Even though the vast majority of recordings are mono-summed below 80 Hz, there is another possible advantage to adding that second amplifier to the system.  Since the amp has a continuously-variable phase control, you could put the subs on one side of the room 90 degrees out of phase with the subs on the other side.  This setup is recommended by David Griesinger, developer of the Lexicon processor.  What this does is introduce an interaural phase difference at low frequencies, which the ear interprets as ambience and spaciousness. 

The H-frame sub is a dipole, isn't it?  Note that below the lowest modal frequency, down in the "pressure zone", a dipole tends to run out of gas even if it's equalized.  The reason is, when the room is too small for even a half-wavelength to develop before hitting the farthest room boundary, in effect the positive and negative sides of the dipole are both working on the same fraction of a wavelength at the same time.  The result is a net cancellation of pressure.  So you might consider augmenting your dipole bass system with a monopole sub down in the pressure zone.

[mgalusha]

Sounds like a very cool product Duke, something I'd point friends at who were looking in that price range. 

[Duke]

Thank you, Mike.

Meanwhile, "Get a real job, ya bum" has surged into 4th place in the polling.  Is this the trickle before the dam bursts?  Are the oppressed masses about to rise up and overthrow the despot??

Stay tuned!!

[ttan98]

Hi Duke,

I build a pair of speakers based on your Jazz module  ie based on  horn/compression driver and 12" woofer combo however all the parts are different. The reason being I cannot find all the parts down under(ie Australia). Basically my speakers were inspired by yours. I am very happy with the sound though. I use it as my main system.

All the best if you decide to proceed with this new product.

Cheers.

[Berndt]

Hi Duke,

I build a pair of speakers based on your Jazz module  ie based on  horn/compression driver and 12" woofer combo however all the parts are different. The reason being I cannot find all the parts down under(ie Australia). Basically my speakers were inspired by yours. I am very happy with the sound though. I use it as my main system.

All the best if you decide to proceed with this new product.

Cheers.

that be imatation
How does Duke inspire so many people?
As an Audio Kinesis owner I am always interested in his new ideas.
Cheers Duke

[Duke]

Thank you all. 

That looks to me like enough interest to justify moving ahead with the project. 

Duke

[Taterworks]

Would you mind commenting on the drivers to be used? I know John J. (AE Speakers) has a new 6.5" mid and midbass driver that's essentially a scaled-down TD driver.

[Duke]

Taterworks, for now I'm keeping the drivers that I'm using under my hat.  I may go public with them once I have completed and introduced my design, and at the least I would tell my customers what the drivers are in case they ever blow a driver and I'm out of the picture (as in, pushing up daisies - until then I'll be doing speakers).

For one thing, it's possible that a more suitable driver than what I have been working with will come along, in which case I would change.  For another thing, suppose I announce that I'm using a certain driver but then I can't get it to work as well as I'd hoped - in that case I would look stupid, and I sure haven't done the driver manufacturer any favors.  Sometimes drivers get discontinued - in fact that happened in this project, and I'm going to go on a tweeterquest in a few weeks.

I don't know the pricing on the new little AE midwoofer, but I'm sure it's well out of the range that I could realistically consider for this project.  No doubt it's excellent.

Duke

[James Romeyn]

Duke
Normal SWARM setup is four subs in mono quasi-X pattern, all four approximately an inch from the adjacent wall.  Normally one diagonal pair of subs are in-phase w/ the main speakers while the polarity/phase of the other diagonal pair of subs is inverted 180-degrees to the main speakers.  (For Russell: this provides bass peformance exceeded by no known system & only matched by stereo floor to ceiling towers w/ four or more drivers per side.  Its greatest performance feature is to replicate the unique "elastic" sound quality of bass in a large/commercial venue; it also flattens modes like nothing else known.)   

If two amps are employed it appears you suggest spatiality may increase with a 90-degree difference vs. 180-degrees above.  Would one diagonal pair of subs remain in-phase w/ the main speakers?  Is the mode nulling effect minimized?     

If two sub amps are employed for stereo bass: Do the subs remain in the original above-described quasi-X pattern?  Are the two subs L of center designated L channel & the two subs R of center designated R channel?  That sounds very interesting & worth trying...

Thanks!   

[Duke]

Ro7939, I've changed my mind about the x-polarity configuration that I once embraced, and now only recommend it for certain situations.

At RMAF last year, I started out with left front and right rear subs in one polarity, and the other two in opposite polarity.  Someone came into the room and wanted to hear a cut with some really deep bass.  He was disappointed when it was missing in action, and so was I.  First chance I got, tried a song I was familiar with that had some really deep synth bass.  It should have made the room shudder, but that didn't happen.  Hmmmm.

After thinking about it a bit, I realized that at low enough frequencies the farthest room boundaries will be less than half a wavelength apart, so that in effect the four subs (two sucking and two blowing, so to speak) would all be working on the same fraction of a wavelength, and would cancel one another out.  After going back to normal polarity for all subs, the room would indeed shudder when called for, but I didn't figure that out until the last day of the show.  Dangit.

So in a room that size my inclination now is to only put one of the subs in reverse polarity, or maybe none of them, depending on which sounds best.

Anyway, the optimum may be using two of those rackmount subwoofer amps, with the phase control on one of them rotated to put it 90 degrees (rather than 180 degrees) out-of-phase with the other.  This way at those ultralow frequencies, their outputs would not sum perfectly in-phase nor out-of-phase, thus approximating the semi-random phase summing in the middle and upper bass region.

Now if your room is big enough relative to the wavelengths you're trying to reproduce, that x-bass setup still works quite well.

[Carl V]

there is a related thread over on AVS....Double Bass Array (DBA)
there are some well thougth out posts in that thread.  The underlying
theory is applicable here.   http://www.avsforum.com/avs-vb/showthread.php?t=837744

[James Romeyn]

Duke
"...very interesting..." as Arne Johnson used to say on Laugh-In.  I'll have to try it & see.  First reaction is that indeed I have missed some low-bass power, but the almost magical & complete elimination of modes (& large room bass effect) is an exceedingly preferable tradeoff (modes so bad in this room that the minimonitors sound better alone than w/ any siting/setup of one or two subs).

Also, I've often wondered if the already great mode-nulling effects might be enhanced by siting one of the four subs above ear level as recommended if only three subs are employed.  This may be more advisable if your above-described method (one sub out of phase/three in) minimizes the mode-null effect vs. the previously recommended two in/two out.  I intend to site one sub above ear level & will post results. 

One other item is this: It occurs to me it might be better to place one sub in phase w/ mains/three subs out rather than three subs in/one sub out as you mention above.  The former may increase mode-null effects up higher where the subs & mains overlap.  At the lowest frequencies the mains are irrelevent, esp when HP-Xd as are mine.  There are few if any things in the audio world resulting in a similar level of bliss as a properly tuned high rez system completely devoid of any midbass mud (AKA the "mudrange" by audio engineers).   

CarlV
My understanding to date after reading maybe 100 pages on the subject is that three is the minimum for the desired effects of the multi-sub approach.  For three, one must be sited above ear level; w/ four all can go on the floor.

Before auditioning I thought three subs was nuts, stupid & why bother.  After auditioning I almost totally reject the notion of fullrange stereo speakers & would consider giving up the hobby w/ less than three subs.  The only exception would be if the room had as close to perfect dimensions as possible.         

[Duke]

One of the key pieces of the Gamma puzzle is apparantly no longer available.  Arrrgh.  I'm trying to find a suitable replacement, but in the meantime this project is on hold.

The good news is, there's another project in the works that will probably come in around two grand a pair. 

Edit 12/16/09:  The bipolar fullrange driver project is the two-grand-ballpark project, and looks like it will be here in late January.  Just waiting on the boxes now.