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Old 3rd March 2008, 03:53 PM   #1
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Default 3-5 mm bitiminous felt ?

Hello all

The plans for the speaker I am finishing call for this as lining. I live in the US and can't find anything this thick. All the audio dampening products get very expensive when you consider I probably need about 20 sq feet.

Any recommended economical alternatives or anyone know where I can find roofing felt this thick?

Thanks

Scott
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Old 3rd March 2008, 03:58 PM   #2
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Hi bug, I moved this over the loudspeakers.

Either at a roofing supply or home depot type store will have it. It's known as #90 or 90 lb. felt. That is assuming you do mean felt (organic) and not fiberglass. If it is the fiberglass based products, you may have to double up on some #40 underlay type sheet.

Either way, I don't consider it first when thinking about damping materials. Can you tell us more or show us a pic of what you are trying to do and maybe someone can help?
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Old 3rd March 2008, 04:30 PM   #3
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Thanks

The directions I am following are here:

http://www.geocities.com/diyproac25/dimensions.htm

I'll look for the 90 pound stuff, although I think it is less than 3 mm. Perhaps I should look at carpet felt. I am not sure how critical this kind of dampening is to the speaker. I am not competent enough to improvise on my own...

Scott
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Old 3rd March 2008, 04:45 PM   #4
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Quote:

"Cabinet lining is 3-5mm bituminous felt damping or similar mass loaded material, 30-50mm polyester (Dacron 200g/m2 density) stuffing/lining. Wall lining and damping is added to all internal walls, except the front wall. It is important not to over specify or use too much lining so the correct amount and density of lining is used in order to maintain the same voice balance of the speaker. This can have more effect on the sound than other over specified and expensive crossover parts (capacitors and inductors). Over stuffed cabinets will result in undesirable and constrained sounding speakers with less bass and midrange voicing. If you cannot find the correct density or thickness, simply peel away estimated amounts of lining."


It gives you the option of polyester lining so I would either head to my local fabric store and get some pillow stuffing or the local hardware store and use rock wool insulation. The nice thing about damping is that it can be tailored to your requirements simply by listening and making adjustments to suit. I hop they're not talking about a bituminous membrane that adheres to the walls and acts like a panel damper rather than the more traditional means of damping the internal waves.
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Old 3rd March 2008, 04:57 PM   #5
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Actually, the bitiminous roofing felt is just what I have seen in the many other speakers built from this plan. Also, the poly fiber stuff from the fabric store (already got that) they mention is supposed to go on top of the roofing felt.
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Old 3rd March 2008, 05:07 PM   #6
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OK, it looks to me like the felt is stapled to the walls and the polyester is added for internal resonance. I wonder how effective the panel damping is when it's not fully adhered, just stapled in place over the wood. Either way, don't be afraid to experiment. Try using whatever thickness you can get and multi-laming to get to 5 mm. If you want to get really fancy, consider using vinyl floor tile fully adhered to the walls. That will help with panel damping better than any felt would. Even the peel and stick kind work well if the inside surface is good and clean.
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Old 3rd March 2008, 05:28 PM   #7
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Thanks a lot

I am heading over to Home Depot now to see what I can find. I'm told there is is a heavy felt that is used in roof valleys and rakes that is sticky on one side. However, what ever I end up using, I will glue it securely to the MDF.

PS I am envious of your big speakers. Perhaps my next project...
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Old 3rd March 2008, 05:30 PM   #8
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Whoa grasshopper, not so fast. That peel and stick stuff has a high solvent content which can have detrimental affects on the drivers. It also stinks. I wouldn't use it unless you are able to install it and leave it for a month before closing up your box.

EDIT: The peel and stick I was referring to was the floor tiles, not the roofing.
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Old 3rd March 2008, 06:33 PM   #9
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Thankyou master. I will continue on my search...
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Old 3rd March 2008, 07:18 PM   #10
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Parts Express has a generic bituminous damping material (P/ N 268-015). It's peel-n-stick. I've used it and unlike other materials it doesn't have a high VOC component.
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