Push Pull vs Normal Distortion Compared

[18Hurts]

I liked your Keystone tapped horn running dual 12's

You say it puts out 6dB more than a ported sub provides? I figured it would be a little higher but every little bit helps.

By the time I figure out tapped horns, horn response, keystone mouths and have it all designed--they will probably obsolete the drivers.

First the single 10", I can screw around with it and really like the keystone mouth. +6dB boost from the alignment will give me 94dB... close enough for garage duty.

[weltersys]

Originally Posted by 18Hurts

I liked your Keystone tapped horn running dual 12's

You say it puts out 6dB more than a ported sub provides? I figured it would be a little higher but every little bit helps.

The dual Lab 12 Keystone was about 7 dB more sensitive than the dual 12 half the size.

Keystone Sub Using 18,15,&12 Inch Speakers
Post #1 has the chart comparing it, post #12 goes over the distortion, which is about the same as the ported cabinet on average.
It would be fairly easy to make a "donut" adapter that would allow the dual 12 Keystone to be run in PP, if it didn't work as well as normal, it could be switched back.

I wish I would have done that experiment, but the BC18115-4 sounded better than the Lab 12s, and could take way more power and still sound clean, so I was not inclined to pursue it too much.

[Patrick Bateman]

I've had some good luck with push pull speakers.

The pictures and graph above are from a push-pull project I did. One enclosure is a front-loaded horn, one enclosure is a tapped horn. We see the following:

• The low-pass effect of a front loaded horn is really nuking distortion at high frequencies
• push-pull seems to be making a noticeable reduction in distortion (look at 2nd versus 3rd in the range of 100 to 400hz)
• If you look at the entire bandwidth range, the tapped horn has more output at the expense of higher distortion. Note that in the real world we would likely use a larger driver with the TH than with the FLH, which would reduce distortion

Here's a B&C 8NDL51 for comparison's sake. I'd say the push-pull Auras do pretty well, particularly since they're under $80 a pair.

[tvrgeek]

Random thought. I always considered Isobaric to be a cheat for a too small motor, but would you get the same advantage in distortion with cone-to-cone facing Isobaric?

[weltersys]

Originally Posted by tvrgeek

Random thought. I always considered Isobaric to be a cheat for a too small motor, but would you get the same advantage in distortion with cone-to-cone facing Isobaric?

Yes, even order harmonic distortion is largely eliminated, leaving the more objectionable odd order left when driven hard.

I used a pair of $5 Sammi 10" in a cone-to-cone facing isobaric tqwp:

$10 (plus wood) 18Hz ISOT-TQWP Sub

Art Welter

[Brian Steele]

Originally Posted by weltersys

Yes, even order harmonic distortion is largely eliminated, leaving the more objectionable odd order left when driven hard.

Seems like a good match for an acoustic bandpass alignment - the isobaric loading will take care of the even order frequencies and the acoustic bandpass could reduce the audibility of the odd-order ones above the system's passband.