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Old 1st July 2011, 09:01 PM   #21
18Hurts is offline 18Hurts  United States
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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.
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Old 1st July 2011, 11:36 PM   #22
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Quote:
Originally Posted by 18Hurts View Post
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.
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Old 31st August 2012, 03:02 AM   #23
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I've had some good luck with push pull speakers.

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.

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

Click the image to open in full size.
Click the image to open in full size.
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.
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Old 1st September 2012, 10:28 PM   #24
tvrgeek is offline tvrgeek  United States
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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?
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Old 2nd September 2012, 06:26 PM   #25
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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
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Old 2nd September 2012, 09:37 PM   #26
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Originally Posted by weltersys View Post
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.
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