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Discussion Starter · #1 ·
I've made a custom speaker enclosure that is primary designed for sound quality. The front baffle is rounded and complex in shape. On the inside, I would like to pour a 1inch layer of epoxy to firm up the cabinet, make things smooth/flat, fix some internal recesses and help with bracing and dampness.

My questions:
1) would a one inch pour around the internal second layer of 3/4 MDF have desirable resonance characteristics? Epoxy is pretty damp so I would assume it would be OK.

2) for those that have poured epoxy on MDF, did you have swelling of the MDF?

3) Would there be any shrinkage of the epoxy that may cause warping once cured?

4) Do you think the epoxy would bind well enough to a vertical surface to withstand the speaker vibrations of two 8 inch woofers?
 

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I don't see why all of your questions couldn't be answered if you'd try some epoxy on some scrap/sacrificial pieces of MDF
 
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I'd definitely do some trials.

As for epoxy adherence, typically it's not a problem but you could drill some dimples here and there to help give the epoxy something to grip better, I'm not talking deep, 1/16" or so should be fine. Just surface variation. Rings or perimeter grooves would be better but if cabinet is made already would be tricky to do. The groove thing is typically done in industry when, say, epoxy-repairing a valve (machine back corroded seats, install locking grooves, epoxy a titanium shim in, machine back, wam, good as new).
 

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make things smooth/flat
Why do you care about that on the inside?

That's a lot of epoxy - $$

If you want damping and are willing to give up that much box volume, get synthetic stone (stone powder in a resin bander - Corian, quartz, etc) countertop remnants and bond them in with Green Glue.
 

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This won’t have any affect on your overall outcome.

To answer some of your questions:

MDF will soak up the epoxy, the thicker it is the less it will soak up. Yes there will be swelling and no it won’t be uniform.

Because the adherence properties of epoxy you can bring it up to verticals without an issue, the dimple idea is still good though.

This is going to cost a lot and I fear it was a solution to a problem you won’t have.


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If you want to mess with epoxy, get some carbon fibre cloth and stick a layer or two on the insides of your cabinet. CF cloth isn't even that expensive and no need for vacuum pumps (unless you make parts for a racing car). You just apply it as if it was fibre glass pretty much.
 

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I've made a custom speaker enclosure that is primary designed for sound quality. The front baffle is rounded and complex in shape.
post some pics. we're always interested in how things cone to be . .
 

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Discussion Starter · #8 ·
I'd definitely do some trials.

As for epoxy adherence, typically it's not a problem but you could drill some dimples here and there to help give the epoxy something to grip better, I'm not talking deep, 1/16" or so should be fine. Just surface variation. Rings or perimeter grooves would be better but if cabinet is made already would be tricky to do. The groove thing is typically done in industry when, say, epoxy-repairing a valve (machine back corroded seats, install locking grooves, epoxy a titanium shim in, machine back, wam, good as new).
Thank you for this information. I will go that route.
 

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Discussion Starter · #9 ·
Why do you care about that on the inside?

That's a lot of epoxy - $$


If you want damping and are willing to give up that much box volume, get synthetic stone (stone powder in a resin bander - Corian, quartz, etc) countertop remnants and bond them in with Green Glue.
How much I'm looking to do will be about a quart. I have a decent amount of time into this so 50$ wont make a difference to me. Ideally, it would help bond some pieces that I couldnt get a clamp on too.

Do you think synthetic stone would bond better than epoxy.

This won’t have any affect on your overall outcome.

To answer some of your questions:

MDF will soak up the epoxy, the thicker it is the less it will soak up. Yes there will be swelling and no it won’t be uniform.

Because the adherence properties of epoxy you can bring it up to verticals without an issue, the dimple idea is still good though.

This is going to cost a lot and I fear it was a solution to a problem you won’t have.
Thanks.
If you want to mess with epoxy, get some carbon fibre cloth and stick a layer or two on the insides of your cabinet. CF cloth isn't even that expensive and no need for vacuum pumps (unless you make parts for a racing car). You just apply it as if it was fibre glass pretty much.
Whats the purpose of the carbon fiber?

I've made a custom speaker enclosure that is primary designed for sound quality. The front baffle is rounded and complex in shape.
post some pics. we're always interested in how things cone to be . .
Ill do that when I'm further in the process.
 

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I've made a custom speaker enclosure that is primary designed for sound quality. The front baffle is rounded and complex in shape. On the inside, I would like to pour a 1inch layer of epoxy to firm up the cabinet, make things smooth/flat, fix some internal recesses and help with bracing and dampness.

My questions:
1) would a one inch pour around the internal second layer of 3/4 MDF have desirable resonance characteristics? Epoxy is pretty damp so I would assume it would be OK.

2) for those that have poured epoxy on MDF, did you have swelling of the MDF?

3) Would there be any shrinkage of the epoxy that may cause warping once cured?

4) Do you think the epoxy would bind well enough to a vertical surface to withstand the speaker vibrations of two 8 inch woofers?
I added aircraft structural epoxy when I assembled a kitchen roll around microwave enclosure that was originally using inserts and cams.
 

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To firm up the cabinet and help with bracing and dampness.
That seems more effective than just epoxy (of course what seems and what is aren’t necessarily the same thing) even some of the very heavy fiberglass weave you can get at West marine etc. It’s like 1/4” thick glass cloth so that and some epoxy would be very beefy.
 

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That seems more effective than just epoxy (of course what seems and what is aren’t necessarily the same thing) even some of the very heavy fiberglass weave you can get at West marine etc. It’s like 1/4” thick glass cloth so that and some epoxy would be very beefy.
Just a single thin layer of CF will do wonders. I have done sandwiches of CF balsawood CF in the past and the result is very rigid.
 
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On the inside, I would like to pour a 1inch layer of epoxy to firm up the cabinet
How much I'm looking to do will be about a quart.
Those must be very small cabinets.


Do you think synthetic stone would bond better than epoxy.
? The stone is a material to be bonded, not a bonding material.

You don't need to do anything extra to make epoxy adhere wood or MDF; it will penetrate and become one with it.

If you bond something using it and try to pull it apart, failure will be either below the surface of the box, or at the interface to whatever you bonded on.
 
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