Been following this one with great interest, since i've been using folded horn subs for PA for a while. Wayne, look at www.stage-accompany.com and look how they have employed forced air cooling into the performer series. ("Air system").

Basic form is a fan, and a speed controller that reacts to averages of progam levels- then adjusts speed of the fan to the conditions.

Also remember that most PA subs are not being used at below 40-45 hz.

Nothing down there, too much potential for sstage rumble, or runaway subsonic feedback, etc. Some systems don't operate below 60 hz.

Larry Acklin

However, what is significant about this new horn is the push-pull plenum, which counteracts motor asymmetry. There is nothing in the LABhorn design that deals with this. It is well-known that the cause for harmonic distortion is primarily due to asymmetries in the motor assembly, not the mechanical suspension or pneumatic loading. That is why shorting rings are used in low-distortion drivers - They counteract the major cause of asymmetry, which is flux modulation. Another way to counteract it is the push-pull plenum arrangent.

There are many things a horn does that reduce distortion, but it cannot address flux modulation. There is no mechanism to restore symmetry. Horns reduce excursion and reduce bandwidth, both of which reduce distortion components. But asymmetry is not reduced by horn loading, so the push-pull plenum has been added to address this. If a woofer with a sufficiently large shorting ring were used, that would do it too.

How long is the pathway and mouth area? Got any Hornresp response predictions of this horn?

The pathway is interesting, I've not seen a horn before that has the pathway split off into two directions. Is it the same as having one pathway with double the area/volume?

The main thing I'm sure of is that the push-pull plenum decreases distortion and that fresh, cool air to the voice coils will do a better job of keeping 'em cool than trapped air in a very small rear chamber. Now I have to do some exploration to find the best ways to exploit these improvements.

Im sure the push/pull config will reduce distortion - John Sheerin did something similar in a dual 10" CSX basshorn, and noted very good improvements in 2nd HD.

Ducting to get cool air from the outside - reminds me of the cold air intake/induction system I put on my car made from 90mm piping :P If you were to do the ducting on the vented pole piece, I think make the piping larger than the vent itself so that the airflow doesnt cause a restriction and start creating noise and air pressure buildup of its own, which would mean more distortion.

Adrian

When you go to the site, click on the SA logo. Go to the performer series, scroll down and click on the air system logo.

Basic info there, and lots of good info in the PDF stuff. I saw a design (beta) where the woofer and mids also had air plenums and cooling.

Dimension that box you are looking at for Delta 15's and you got a winner.

Larry

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