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Timtom 26th March 2007 01:40 PM

Mackie Sub Tower
Hi, I posted this also on the AVS forum area but wanted to kick as may cans as possible...I am interested in some feedback on creating a "tower" stand for my HR 824's that incorporates a side loaded sub. Bully Subs did what they called the "Bully Mac" but I would like to keep a slender profile. I would build a 10" wide x 30" tall 16" deep box and use either a 12" or 15" driver. I could go with a 12" & a passive like the North Creek "Thunder" design

Driver suggestions?
Use a servo design since the mackie's are also servo controlled?
Can I use separate hi power "Pro" amps or would I be better of with a plate amp?

I envision a seamless tower profile 10w x 46t x 16d

Also should I point the side drivers towards one another for gain or way from the center....80Hz down

Timtom 27th March 2007 06:34 AM

Any thoughts at all?

taloyd 27th March 2007 02:27 PM


If you don't want an excessively large cabinet to match the width of the Mackie monitors, look into subwoofers based on the Peerless XLS and passive radiator combo (like the North Creek Thunder). You might also want to look into Rythmik Audio... they're known for top-quality bass, and their prices are VERY reasonable considering the product.

Also, their is nothing servo-controlled about the Mackie's... they're a fairly straightforward two-way monitor, with a passive radiator in back, and a controlled directivity waveguide for the tweeter.

The Rythmik Audio, however, ARE servo-controlled, and that's partially responsible for the excellent performance.

Hope this helps...


Timtom 27th March 2007 10:55 PM

Hmmm, They advertize as "Servo controled" and show a "Bass servo control loop" tried to a motion detector on the layout schematic...Is this not "Servo Controlled":whazzat:

taloyd 28th March 2007 12:08 AM


Okay, dug more into it... from:

The print advertisements for the HR824 make much of the direct-coupled servo loop between amplifier and speaker, from which one might infer that the HR824 features a distortion-reduction accelerometer feedback system. A look at the distortion measurement curves does not confirm this hypothesis; the distortion curves show a well-behaved characteristic but still have a conventional rise in distortion with deepening bass. Direct observation (yes, we looked inside) found only a two-wire connection to the woofer, not an accelerometer scheme. So we can assume that some sort of motional feedback/negative output impedance “servo loop” is used. The ad mentions “motional parameters,” a partial confirmation of the latter assumption.

Yamaha's YST (and the Mackie design) basically (if I understand correctly, which I may not) attempt to create a transconductance (current) amplifier out of a conventional voltage amplifier. As electromagnets (speakers) function based off of current, not voltage, having a current amplifier bypasses thermal compression and other issues tied to variable impedance, but is not exactly a servo system. In fact, a transconductance amplifier is more single-ended than a voltage, as it somewhat ignores the impedance of the load and will simply dump current into it.

In either case, I would still suggest Rythmik Audio as the best match for the Mackie's or any other 2-way speaker. They build a very well engineered product, and you would get potentially superior bass reproduction compared to a conventional subwoofer, unless you go the huge Sd/Vd route (multiple 15's, huge pro-amps, EQ to compensate for room modes, etc.). Due to the servo control of the Rythmik subwoofers, the box size is not paramount to the design. A larger box will increase transducer sensitivity, and lower power compression... however power compression is corrected for by the servo, so it affords much more leeway than a conventional subwoofer. The advantage of the Peerless XLS/radiator combo is you can have a VERY small box. But it cannot compete with the Rythmik product in terms of distortion components, etc.

Hope this helps...

-Tal Allweil

Timtom 28th March 2007 06:28 AM

Well, servo or not they seem to do a pretty good job at sound reproduction.

I am interested in the Rythmic subs, I have read very good reviews of them. The servo feture, that only works with their amp, correct?

I have a seperate 350w/channel that I would like to use for this project but it may not work in "servo" mode. I suppose I could implement a LT circuit but I think that can only be used with a sealed cabinet.

I suppose if I want to keep from buying another amp, the Peerless/Passive combo my be the best outlet

Foxx510 28th March 2007 07:31 AM

Here is another design you could adapt using the peerless woofer Link. You would need your own sub filter/crossover though, but the suggested response curve is in the article. I've heard a small sealed 12" sub, I liked it a lot.

sreten 28th March 2007 09:34 AM


sounds like an amplifier with (active) output resistance making it
more of a current source, this then changes the driver Qts, allowing
the box alignment to be an overdamped relatively high efficiency.

The basis of Yamaha's "air bass" system as I understand it, and
not particularly difficult to design either, if you understand it.




paulspencer 2nd May 2007 07:26 AM


I have the Rythmik DS12 kit and highly recommend it!

The size you mentioned looks about right for a sealed 12" Rythmik. I was interested in the Rythmik for a long time but was put off by not being able to use my existing pro amp which has kilowatts of power! I'm now moving from two 12" drivers with a monster amp and 23mm xmax to two of this kit with 18mm xmax and 370w to each driver. The design is quite clever as it uses power more effectively than many other subs, and the servo control means much greater accuracy.

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