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Old 1st July 2011, 03:56 PM   #11
a.wayne is offline a.wayne  United States
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What about compound loading vs this PP version , you guys ever compare before ...?
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Old 1st July 2011, 04:18 PM   #12
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Originally Posted by 18Hurts View Post
Do you think the lowering of harmonic distortion with push-pull will lower the stress on the woofers during maximum drive levels? Every little bit helps to keep those things alive. Since horn loading really puts the pressure on drivers, the distortion reduction could increase longevity of the driver?

Thanks for posting your results, as with everything--it does work but it all depends on what you want. In the classic battle between size and reliability so would two drivers in the same box push-pull be more reliable than two individual boxes? Would lugging around the larger and heavier push-pull be worth it reliability wise VS two lighter and smaller boxes?

Thanks for throwing another variable in my quest to build a horn loaded subwoofer, Art! My subwoofer design is growing faster and larger than the national debt.
The closer the PP speakers are to each other, the more effective the distortion reduction is, so separate boxes may not be a good idea.
That said, separate chambers for each driver reduces distortion in any configuration.

Push pull can reduce even order (the "good sounding" LOL) distortion, but does not decrease excursion, so I don't see it as offering an increase in the longevity of the driver.

Although I'm all for reducing LF distortion, when distortion is lacking the tendency for many sound operators is to turn up the level, pushing the clean speakers harder than the louder sounding distorted speakers.

Assuming the adhesives are not cooked out of the speaker, driver longevity is related to excursion, the harder the driver is pushed, the shorter the lifetime before the cone and spider wear out.
It is common for speakers not pushed much beyond Xmax to last decades, but a speaker driven to Xlim may only last seconds.

Last edited by weltersys; 1st July 2011 at 04:38 PM.
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Old 1st July 2011, 04:32 PM   #13
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Originally Posted by a.wayne View Post
What about compound loading vs this PP version , you guys ever compare before ...?
The purpose of my test was to determine the difference in distortion using PP vs normal loading.
If by compound loading, you mean mounting the speakers in a plenum, sometimes called a slot, no what you see in the first four posts are what you get.

A plenum works as a low pass filter, so it will reduce upper distortion products on PP or normal configurations.

The purpose of my test was to determine the difference in distortion using PP vs normal loading. Adding a plenum as another variable would have required double the time, as it stands the test results took around 16 hours.
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Old 1st July 2011, 04:35 PM   #14
a.wayne is offline a.wayne  United States
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compound loading as in one driver mounted behind the other no slot ..
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Old 1st July 2011, 05:31 PM   #15
badman is offline badman  United States
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Quote:
Originally Posted by 18Hurts View Post
Do you think the lowering of harmonic distortion with push-pull will lower the stress on the woofers during maximum drive levels? Every little bit helps to keep those things alive. Since horn loading really puts the pressure on drivers, the distortion reduction could increase longevity of the driver?

Thanks for posting your results, as with everything--it does work but it all depends on what you want. In the classic battle between size and reliability so would two drivers in the same box push-pull be more reliable than two individual boxes? Would lugging around the larger and heavier push-pull be worth it reliability wise VS two lighter and smaller boxes?
No increase in lifespan.

Size concerns are just that- you can make smaller less efficient subs if portability is a concern, or skip the benefit of Push Pull. "Worth it" is a value proposition, nothing you can say "yes" or "no" to on someone else's behalf. Depends on how strong your back is or if you have a helper or or or...
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Old 1st July 2011, 05:42 PM   #16
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Originally Posted by a.wayne View Post
compound loading as in one driver mounted behind the other no slot ..
That sounds like what is usually called an isobaric loading.
Didn't do that, either.
A photo of the cabinet in normal and PP is in the first post.
The tests were ported and sealed , PP and normal, 400 and 800 watts.
The 800 watt tests were only done on the sealed cabinet, as 49 volt drive level may have exceeded the Lab 12's Xlim at 20 Hz in the ported cabinet.
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Old 1st July 2011, 08:06 PM   #17
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Nice rock!

I've always found that PP does help but only when the drivers are pushed hard enough to reveal the asymmetry of the suspension.
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Old 1st July 2011, 08:19 PM   #18
18Hurts is offline 18Hurts  United States
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Can't blame a guy for asking

My Iso 15's in a WAF approved box (the reason behind the madness) works very well but I'm moving towards horns. I do prefer to use push-pull in tapped horns to even out the frequency response and hoped I could gain a little more stability--guess not.

My back can handle dual-woofers but if I can get the same thing with two boxes, my back is not getting any younger. Thanks for the information again and it looks like I'll be modeling push/pull VS two boxes and figure it out from there. I'm leaning towards two boxes for ease of moving, more flexibility for placement etc.
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Old 1st July 2011, 08:21 PM   #19
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Originally Posted by revboden View Post
Nice rock!

I've always found that PP does help but only when the drivers are pushed hard enough to reveal the asymmetry of the suspension.
Thanks, both the rock and the speakers are for sale if you are interested .

Art
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Old 1st July 2011, 08:35 PM   #20
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Quote:
Originally Posted by 18Hurts View Post
Can't blame a guy for asking

My Iso 15's in a WAF approved box (the reason behind the madness) works very well but I'm moving towards horns. I do prefer to use push-pull in tapped horns to even out the frequency response and hoped I could gain a little more stability--guess not.

My back can handle dual-woofers but if I can get the same thing with two boxes, my back is not getting any younger. Thanks for the information again and it looks like I'll be modeling push/pull VS two boxes and figure it out from there. I'm leaning towards two boxes for ease of moving, more flexibility for placement etc.
Haven't heard of any model that will predict what PP will do from regarding sound quality or distortion.
Push pull in TH is a different animal than in FLH, check out Josh Ricci’s DataBass tests on his new Gjallerhorn compared to a DTS-10 before you make assumptions that dual drivers even out the frequency response or PP lowers distortion.
As far as your back, if you are not actually lifting cabinets, just rolling them around, one large box is more convenient than two smaller boxes, and overall weighs less.
That said, my Keystone sub (double the size of the dual Lab 12s tested here) is as big a cabinet as I want to deal with, I'll leave the Gjallerhorn, 12Pi, LABsub etc. to those with crew.

Art Welter
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