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Problems finding 1" MDF - do I really need it?

post #1 of 15
1/17/13 at 8:27am
Thread Starter 
I am building a this sub cabinet (60 L) that calls for 1" thick MDF, but I cannot find that anywhere and I have called a dozen building supply and lumber stores in Houston.

Can I get away with 3/4" MDF and address the baffle separately, perhaps doubling it up or doing MDF over a plywood layer for added strength? Or should I do two layers of 1/2" thick MDF?

I have built plenty of subs boxes in my day but never with 1" MDF, but I don't want to short change myself.
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post #2 of 15
1/17/13 at 8:41am
I can't think of any scenario where 1" MDF would be required. Proper bracing is effectively the same as doubling the wall thickness. I would run a double baffle, but other than that 3/4" is plenty sufficient. I can't imagine the weight of a complete 1" MDF cab.
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post #3 of 15
1/17/13 at 9:01am
Quote:
Originally Posted by bass addict View Post

Proper bracing is effectively the same as doubling the wall thickness.
A lot more than that. Imagine that the colored squares below are panel to panel braces, viewed end on:


The red brace alone gives the panel the same stiffness as does doubling the panel thickness. Adding the blue braces gives the panel the same stiffness as does quadrupling the panel thickness.
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post #4 of 15
1/17/13 at 12:02pm
Thread Starter 
Awesome info, thanks guys. I did find a place that sells a 4'x8' 1" thick MDF sheet for $57/sheet, but based on your input I am going to use 3/4" MDF and incorporate the proper bracing, which the plans call for one middle brace, but I might add two and make the box slightly larger to compensate.
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post #5 of 15
1/17/13 at 12:33pm
Quote:
Originally Posted by Aaron_G View Post

Awesome info, thanks guys. I did find a place that sells a 4'x8' 1" thick MDF sheet for $57/sheet, but based on your input I am going to use 3/4" MDF and incorporate the proper bracing, which the plans call for one middle brace, but I might add two and make the box slightly larger to compensate.
I wouldn't brace it according to the plans. For one thing braces near the corners are wasted material, as that's the strongest part of the box and doesn't need bracing. But more important is that bracing the front to the back is just as necessary as bracing the top to bottom and sides to each other.
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post #6 of 15
1/17/13 at 12:49pm
Quote:
Originally Posted by Aaron_G View Post

...I have called a dozen building supply and lumber stores...
You are looking in the wrong place. You need to go to a place that supplies the cabinet trade. Look for "hardwood". There are places in Huston that can supply what you are looking for.
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post #7 of 15
1/17/13 at 1:29pm
Quote:
Originally Posted by Bill Fitzmaurice View Post

A lot more than that. Imagine that the colored squares below are panel to panel braces, viewed end on:


The red brace alone gives the panel the same stiffness as does doubling the panel thickness. Adding the blue braces gives the panel the same stiffness as does quadrupling the panel thickness.

This is great info. Thanks for sharing this.
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post #8 of 15
1/21/13 at 12:14pm
Thread Starter 
Quote:
Originally Posted by Bill Fitzmaurice View Post

I wouldn't brace it according to the plans. For one thing braces near the corners are wasted material, as that's the strongest part of the box and doesn't need bracing. But more important is that bracing the front to the back is just as necessary as bracing the top to bottom and sides to each other.

I don't follow. The plans call for bracing down the center of the cabinet, parallel to the face of the sub, not near the corners. I could add some threaded rod bracing from the front panel to the back panel, but given the location of the sub and the port I don't see how I could add the same type of bracing from front to back.
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post #9 of 15
1/21/13 at 12:16pm
Thread Starter 
Quote:
Originally Posted by Colm View Post

You are looking in the wrong place. You need to go to a place that supplies the cabinet trade. Look for "hardwood". There are places in Huston that can supply what you are looking for.

Thanks, I will keep that in mind.
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post #10 of 15
1/21/13 at 1:46pm
Quote:
Originally Posted by Aaron_G View Post

I don't follow. The plans call for bracing down the center of the cabinet, parallel to the face of the sub, not near the corners. .
I see a 'window' brace, which resembles the picture below left, albeit a much fancier iteration. It's got plenty of material in the cab corners. A more effective version that uses less material is shown below right.
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post #11 of 15
1/22/13 at 7:12am
Thread Starter 
Quote:
Originally Posted by Bill Fitzmaurice View Post

I see a 'window' brace, which resembles the picture below left, albeit a much fancier iteration. It's got plenty of material in the cab corners. A more effective version that uses less material is shown below right.

AHHH, understood now. A picture is indeed worth 1000 words! Thanks for clarifying.
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post #12 of 15
1/22/13 at 7:14am
Thread Starter 
BTW, would 3/4" MDF material be sufficient to make that type of brace? Should I double up two pieces of 3/4" MDF or is that overkill?
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post #13 of 15
1/22/13 at 7:59am
Quote:
Originally Posted by Aaron_G View Post

BTW, would 3/4" MDF material be sufficient to make that type of brace? Should I double up two pieces of 3/4" MDF or is that overkill?
I don't care for MDF as a brace material, being rather brittle it easily will snap, though once installed that's no concern. In terms of the required strength 1/2" plywood is adequate.
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post #14 of 15
1/22/13 at 8:04am
Thread Starter 
Quote:
Originally Posted by Bill Fitzmaurice View Post

I don't care for MDF as a brace material, being rather brittle it easily will snap, though once installed that's no concern. In terms of the required strength 1/2" plywood is adequate.

That seems reasonable. I can manage to build the brace with some 1/2" plywood.

I appreciate your input, it helps greatly.
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post #15 of 15
1/22/13 at 8:18am
Quote:
Originally Posted by Aaron_G View Post

I am building a this sub cabinet (60 L) that calls for 1" thick MDF, but I cannot find that anywhere and I have called a dozen building supply and lumber stores in Houston.

Can I get away with 3/4" MDF and address the baffle separately, perhaps doubling it up or doing MDF over a plywood layer for added strength? Or should I do two layers of 1/2" thick MDF?

I have built plenty of subs boxes in my day but never with 1" MDF, but I don't want to short change myself.

Try a google search for architectural lumber and your zip code or zip code of nearest, largest city.
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