Speaker panel deadening mix of particles + hardener ? - diyAudio
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Old 25th June 2015, 12:12 AM   #1
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Default Speaker panel deadening mix of particles + hardener ?

Posts about this might already be on the Forum so, please steer me to them.

If not, here we go: for those of us who build cabinets with MDF or PLY and avoid thickness walls above 1 inch, there are resonances -- even with bracing / foam sheets / fluffy fill.

So, it seems to me that an emulsion of some goopy liquid -- either fast cure epoxy or slow cure glue -- containing ultra-clean sand or other minute particles -- could be poured onto interior sides of the cabinet one by one as each lays flat on a worktable.

Then cured slowly at the right speed to prevent "checking" + minimum shrinkage. Has anyone found the emulsion and particles -- with how to go about doing the cure process ??

Thanks muchly in advance . . . Steve
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Old 25th June 2015, 12:26 AM   #2
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Wont help much. You will just add some mass, and perhaps a tiny bit of damping. This will just lower the resonant frequencies of the panel.

Making the panel very thick both increases mass and stiffness.

I have always fantasized about ways to DIY honeycomb out of resin coated cardboard tubes (lots and lots of short sections) and 1/4" thick hardboard. Never had the guts to try it!
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Old 25th June 2015, 01:20 AM   #3
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Quote:
Originally Posted by stephend1714 View Post
Posts about this might already be on the Forum so, please steer me to them.

If not, here we go: for those of us who build cabinets with MDF or PLY and avoid thickness walls above 1 inch, there are resonances -- even with bracing / foam sheets / fluffy fill.
Cross bracing works.

Use wood braces glued to the centers of each pair of panels on opposite sides of the box.
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Old 30th June 2015, 04:03 PM   #4
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Offset the braces a bit from center to break up the unsupported parts of the panel into different sizes. That way only part of any panel can be excited at any time.
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Old 30th June 2015, 05:09 PM   #5
ilardi is offline ilardi  United States
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Some years ago I had read about a commercially available sound deadening compound (Quietcote???) that included, essentially, the components of joint compound (limestone etc.) and magnesium sulfate (epsom salt) mixed in with a polymer. So figured I would combine joint compound, epsom salt and tacky glue and spread it on the interior of a mini monitor cabinet (about a 1/4 inch thick coating) that I was building. According to some crude measurements I made with an accelerometer it did make a small but measurable difference. I am not sure it made an audible difference but I can say it didn't seem to hurt, since after several years of living with them I am still surprised that my mini monitors sound pretty good.

To give credit where credit is due, I think I first read about combining joint compound with tacky glue in a North Creek Audio brochure. Also, there appears to be some scientific support for the use of magnesium sulfate since there are numerous papers that show that much of the sound absorption at certain frequencies in sea water is due to magnesium sulfate. Whether that has any applicability to its use in non aqueous uses or when the absorbing volume is very small, is, I think, open for debate.

In any event, joint compound, epsom salts and tacky glue are all pretty cheap. So it doesn't cost much to experiment. Speaker builders have, for ages, sworn by lining their cabinets with roofing or bituminous felt. So I am at least open to consider that a coating of equivalent thickness could be made to work.
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Old 30th June 2015, 05:15 PM   #6
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Quote:
Originally Posted by ilardi View Post
lining their cabinets with roofing or bituminous felt.
That would be self adhering membrane aka peel and stick, not roofing felt. Felt would not do much.
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Old 30th June 2015, 07:57 PM   #7
ilardi is offline ilardi  United States
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Well actually Vance Dickason in his LDC recommended stapling multiple layers of roofing felt to the interior sides of the cabinets as a cheap and effective dampening method.
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Old 1st July 2015, 03:08 PM   #8
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Quote:
Originally Posted by ilardi View Post
Well actually Vance Dickason in his LDC recommended stapling multiple layers of roofing felt to the interior sides of the cabinets as a cheap and effective dampening method.
Hi Terry,
I believe that would be for the internal standing waves not panel damping.
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Old 1st July 2015, 03:30 PM   #9
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Quote:
Originally Posted by CharlieLaub View Post
I have always fantasized about ways to DIY honeycomb out of resin coated cardboard tubes (lots and lots of short sections) and 1/4" thick hardboard. Never had the guts to try it!
https://www.vacupress.com/product/re...ted-honeycomb/
I have used this quite a bit to make panels that look massive but are light weight. I like to use unibond 800 for the glue.
https://www.vacupress.com/product/unibond/
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Old 1st July 2015, 03:49 PM   #10
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Quote:
Originally Posted by stephend1714 View Post
Posts about this might already be on the Forum so, please steer me to them.

If not, here we go: for those of us who build cabinets with MDF or PLY and avoid thickness walls above 1 inch, there are resonances -- even with bracing / foam sheets / fluffy fill.
Google on "Constrained Layer Damping"
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