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Old 4th November 2004, 07:12 PM   #1
BobA is offline BobA  United States
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Default Damping material

I am in the process of restoring a 30 year old pair of EPI 150s, which is a simple two-way in a 1.6 cubic foot box. I plan to replace the drivers and crossover, and have had no problem locating suitable replacements.

However, I noticed that the side panels of the cabinet (3/4-inch particle board, I think) are really noisy! They vibrate all over the place, and you can hear the distortion. The boxes are stuffed with a little foam which obviously isn't doing the job.

I could really use some recommendations regarding the best way to deaden the cabinet. I've read a little about products like Blackhole 5, but have no practical experience. Any suggestions?
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Old 4th November 2004, 07:50 PM   #2
tiroth is offline tiroth  United States
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I guess the question is, where is the noise coming from?

Rattling joints?
Loose material in the walls themselves?
Flexing of the walls?
Transmission through the walls?

I think the strategy is different depending on the problem. #1 and #2 would be the most likely source of a major problem. Unfortunately, I'm not sure there are easy fixes.

If you are talking about relatively minor improvements needed than bracing would fix #3 and some combination of fill (fiberglass, wool) and/or damping (e.g. BH5) to address #3-4.

If you give more information I'm sure the experts will chime in.
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Old 4th November 2004, 10:34 PM   #3
RAW is offline RAW  Canada
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http://www.madisound.com/cgi-bin/dis...gi?read=321589

This was a topic ove at the Mad board.

I posted my few findings .

Enjoy

Al
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Old 4th November 2004, 10:54 PM   #4
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It's probably just 3/8" or 1/2" particle board. Typically DIYers use 3/4" MDF or quality plywood and still use bracing. Damping materials are going to have little effect compared to proper bracing in a cab made of thin particle board, so first figure out how to brace those relatively large unbraced panels without taking up too much volume. Then use damping material to damp the internal reflections.
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Old 5th November 2004, 04:58 PM   #5
tiroth is offline tiroth  United States
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I thought I heard of problems with old PB where internal "chips" delaminated due to age/moisture/vibration/damage. These chips then rattled when certain frequencies excited them. This particular problem seems unfixable.
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Old 7th November 2004, 06:53 AM   #6
BobA is offline BobA  United States
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Bracing seems like a logical first step as long as I can do it without significantly effecting the box volume (which I'm sure I can).

Assuming that bracing will be added, what about using damping materials? Will the use of BH5 (or similar products) eliminate the need for stuffing the box, or should I still add a few pounds of acousti-stuff?

Thanks for your input.
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Old 7th November 2004, 03:02 PM   #7
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Keep in mind that bracing needs to connect opposite walls to have much affect. Depending upon the type of bracing used, it can go a long way to damping internal waves. Something on the panel directly behind the driver to diffuse/absorb to prevent reflections back to the cone is always good (like a handful odd angled pieces of wood). Polyfill will help offset the volume used by bracing.

IMHO expensive damping products are a waste of money and overkill. Polyfill and paper egg crate are economical and work fine for damping and diffusing.

If you remove the drivers and it really is particle board, then you may have a problem if screws are used due to the particle board being weak and "crumbly". It's a good idea to reinforce the inside of the baffle where the screw holes are by gluing in some pieces of plywood and switching to T nuts.
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Old 8th November 2004, 03:09 AM   #8
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I've burned a few EPI 150 boxes (alot more 100s thou)

They are fairly standard vinyl covered LDF boxes made with the machines that cut 45 degree groves and fold the box arounf the front & back baffles.

Bracing & changing to fiberglass stuffing (used to better effect in older EPis) is what i would do at a minimum.

At maximum, you would start over again... there is a lot of ground in-between.

The tweeters are quite decent, the mid-woofers can benefit from some tweaking.

dave
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