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Old 11th November 2009, 04:52 PM   #1
konut is offline konut  United States
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Default Bracing for Sealed Sub

I have a UFW-12 sub from AV123 that recently has been upgraded, with a kit from the manufacturer, with a new amp and driver. This is a thread, on the AV123 forum describing the installation of the kit.
http://forums.av123.com/showthread.php?t=42013
There is another company that is offering a kit for lining the walls of the sub with Blackhole 5.
UFW-12 Black Hole 5 Cabinet Upgrade Kit
I've been thinking about this A LOT lately. While I can appreciate the wisdom of lining all sides with Blackhole 5, to deaden all walls, I don't think its justified cost wise. Maybe I've been thinking about this all wrong, but here is my line of reasoning about this. I've always made the practice of using dampening on only 1 opposing side of an enclosure/room to stop resonances/modes from developing. Now I realise that,at the lowest bass frequencies, it is all but impossible to excite a mode because of the distances involved with bass frequencies in a sealed cabinet, and that all one is trying to accomplish is preventing the walls from any type of vibration. Toward that end, what I was thinking about was to use some basic plumbing parts to push the resonant frequencies up on the top, bottom, and sides, so there is no way they would vibrate, and lining the top and one opposing wall with Blackhole 5. Picture this: with flanges on opposite ends of 2 pipe nipples with a tee in the center, it would be possible to turn the tee so it will exert force on the flanges, bracing the center of the cabinet(top and bottom), the same setup on the side walls. Have you ever played a bongo drum? If you put your thumb in the center of the head and hit it, the frequency is much higher than without the thumb pressure. Same principle. Does this make ANY sense whatsoever? Or am I just nucking futz?
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Last edited by konut; 11th November 2009 at 05:16 PM.
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Old 11th November 2009, 09:13 PM   #2
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Sure, do it all the time. Not too much work to install a couple of cross bracing in commercial subs, well worth the effort. Bracing can be made from any material, i guess.
I normally use wood secured with glue. One difference between this and the compression method you suggested is that the glue would resist movement of the panels in both inward and outward directions. The compression method might distort the box slightly, if you crank it too high. I suppose it doesn't really matter.
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Old 11th November 2009, 11:15 PM   #3
konut is offline konut  United States
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Thanks, appreciate the reply. I know that I can't expand the brace too much or box deformation, or destruction, is possible. I don't think I would have to expand it much to get the desired effect.
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Old 12th November 2009, 07:46 AM   #4
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As it's sealed, it won't make much difference - they're very lenient when it comes to changing the size a little.
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Old 12th November 2009, 08:14 AM   #5
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With a sub, bracing is primarily to keep the walls from ballooning. Stiff panels (why is way better than MDF here) and braces that significantly tie opposite sides together,

dave
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Old 13th November 2009, 12:07 AM   #6
konut is offline konut  United States
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Hi Dave, thanks for chiming in. Are you saying that the enclosure is naturally prone to expand rather than contract during the rarefaction phase? If that is the case then maybe it would be a better idea to screw the flanges to, say, a 6"X6"X 1/2" piece of wood, glue the wood in place, and contract the pipe, with the tee, to generate a pincushion effect on the cabinet to counteract the ballooning. Or, am I just over thinking this?
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Old 13th November 2009, 12:51 AM   #7
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When i say balloon, the picture that pops into mind is the sides curving outward, but when the woofers move out, the opposite happens, the walls try to bow in. So maybe breathing might be a better term, but then you might think it moving air in & out of the box (which does happen with unfinished MDF)

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