Making strong box - Woodworking Talk - Woodworkers Forum
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post #1 of 6 Old 12-31-2017, 10:46 AM Thread Starter
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Making strong box

I'm making a subwoofer box for my son's truck. Space is an issue so I'm going to put the box under the front seat. I'm using 1/4 inch Birch for the box, and want to strengthen and stiffen the wood. I have two products that I use quite a bit, and would like your opinion on best one for this project. The first product is LiquidWood and WoodEpox. I have used these products exclusively on rotted or cracked wood previously, but think they might be good here. The second product is 2-part epoxy resin and maybe fiberglass cloth. Both the LiquidWood and resin soak into the wood, though the resin will form a hard shell.
Does LiquidWood strengthen good wood? I like the way it work on rotten wood, but do not know if it helps otherwise. I prefer to use the LiquidWood because it is easier to work with and I think it will give better sound than a resin finish. The Birch is not strong enough on its own, at least not at 1/4 inch, and anything thicker will not give the cubic feet of space necessary for the subwoofer to operate.
Your comments and suggestions are most welcome.
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post #2 of 6 Old 12-31-2017, 12:04 PM
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The two part epoxy and fiberglass will strengthen the structure. Know nothing about the other product, but highly doubt it is anything near as good.

What kind of strength are you attempting to achieve? I am surprised that the subwoofer will even fit under the seat, let alone in a box.

George
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Last edited by GeorgeC; 12-31-2017 at 12:08 PM.
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post #3 of 6 Old 12-31-2017, 12:07 PM
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As George said - 2 part epoxy and fiberglass cloth. The others you mention are penetrating epoxy which is great for soaking in the wood to seal it but do little for strength.
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post #4 of 6 Old 12-31-2017, 12:28 PM Thread Starter
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Thanks for your replies and I appreciate the advice. Resin and cloth it is!

"What kind of strength are you attempting to achieve? I am surprised that the subwoofer will even fit under the seat, let alone in a box."
I need all sides to have no flex at all to achieve best performance out of the subwoofer. This will be a sealed box. I'm going with a sealed box because they require less space than ported. I"ve done a mock up with cardboard and can get just enough volume with 1/4 wood, so my challenge is to make the thin wood strong.
The box will go under the passenger's seat of a Dodge Ram. A manual vice power seat. Outside measurement of box are 15.5 x 10.5 x 6. Quarter inch plywood gives me .47 cubic feet interior volume, half inch gives .37. Subwoofer has to have .35, and I want to line interior of box with polyfill.

Thanks for excellent inputs. Randy
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post #5 of 6 Old 12-31-2017, 02:25 PM
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I agree with the resin and cloth option, but how big is the sub and what wattage will it be handling? Those 15x10 surfaces are likely to be susceptible to harmonics, even with the fiberglass coatings. Have you ever used DynaMat on the inside of speaker enclosures? I've had good results with it on sheet metal cabinets for sound and vibration deadening.

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post #6 of 6 Old 12-31-2017, 04:17 PM Thread Starter
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Originally Posted by Jim Frye View Post
I agree with the resin and cloth option, but how big is the sub and what wattage will it be handling? Those 15x10 surfaces are likely to be susceptible to harmonics, even with the fiberglass coatings. Have you ever used DynaMat on the inside of speaker enclosures? I've had good results with it on sheet metal cabinets for sound and vibration deadening.
The speaker is an 8 inch semi-shallow speaker, Skar VD8 if you are familiar. It will be powered by 380 watts.
I have only used the polyfill inside the two speaker enclosures I have made. My plan is to put two coats of resin and one layer of cloth on the outside of the box. After resin dries I will lightly sand and spray auto undercoating on entire box. I'll attach the top to the box with resin, then put the polyfill on the inside of the box, over the undercoating.
Do you think polyfill will be sufficient to prevent harmonics?
I've got to say that I am surprised by the stiffness of the birch, even at 1/4 inch. This box will be a brick when the resin dries.
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