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Old 1st August 2007, 07:19 AM   #1
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Default Wood is becoming comfusing.

Hello.

I'm planning on building a speaker similar to Nomad Audio's Ronin D's. The site states that they are constructed of Biscuit Jointed Cross-Ply Bamboo Panels.

I would like to build it out of a hardwood. That way, it would be easy to just sand, stain, laquer, etc...

I have read that there can be issues with hardwood cracking, and expanding.

I would just go ahead and make it out of some MDF I have lying around, but if I do that, there is no way that I can have them finished. I cannot veneer for the life of me. Nor do I wish to paint them. I want a real wood look.
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Old 1st August 2007, 09:27 PM   #2
y8s is offline y8s  United States
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how about hardwood-clad MDF? use 1/4" thick hardwood and adhere it to the MDF. That way if there are gaps or whatnot, it will not affect the acoustics. And it's easier to finish for you.
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Old 1st August 2007, 09:48 PM   #3
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Default Re: Wood is becoming comfusing.

Quote:
Originally posted by wafflesomd
I would like to build it out of a hardwood. That way, it would be easy to just sand, stain, laquer, etc...

I have read that there can be issues with hardwood cracking, and expanding.
Go ahead, don't sweat it.
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Old 1st August 2007, 10:47 PM   #4
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Default Re: Wood is becoming comfusing.

Quote:
Originally posted by wafflesomd

I would like to build it out of a hardwood. That way, it would be easy to just sand, stain, laquer, etc...
I would just go ahead and make it out of some MDF I have lying around, but if I do that, there is no way that I can have them finished. I cannot veneer for the life of me. Nor do I wish to paint them. I want a real wood look.
Hi,
With all due respect, if you can't veneer you aren't ready for all of the problems with solid wood.
Read here:
Which wood?

That's a recent thread.
I can veneer and have worked with solid wood for a long time. I wouldn't even consider a box made from solid.
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Old 1st August 2007, 11:24 PM   #5
preiter is offline preiter  United States
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There's always plywood.

You have the exposed ends to deal with, but sometimes that can look nice.
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Old 2nd August 2007, 12:31 AM   #6
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Default Another option - Veneered Plywood with Hardwood Corners

Another option, build your MDF boxes. The clad with 1/4" hardwood plywood (or 3/4" hardwood plywood). I use birch, I like the grain the best and it is the cheapest :-).

The secret is to flush trim each side to the MDF box (leaving the corners exposed). Glue in an oversized piece of hardwood and flush trim that. Then do your typical staining and top coating.

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Old 2nd August 2007, 07:01 AM   #7
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Hardwood will only crack if it has not been seasoned properly, and dried to EMC (equilibrium moisture content) in the environment they are goimg to live, or you do not allow the wood to move as the humidity changes. It is possible to build speaker cabinets from solid wood and have no issues with them, but you must put significant design effort into them so the wood can expand and contract with the weather without becoming stressed. I have built 3 pairs from solid Jarrah and have had no issues, and Jarrah is a Eucalyptus which are well known to be unstable. The panels have of course moved and opened up gaps in the joins, but the joins are sealed with rubber so they remain airtight and are designed to move so there have been no issues - i.e. no splits or leaks or any other problems. It is important to know that wood expands and contracts much more across the grain than along the grain. You can safely ignore movement along the grain, but must design carefully for movement across the grain. Tall and narrow speakers (e.g. TL) are therefore much better suited to solid wood than fat speakers. Wide expanses of wood across the grain are to avoided, as is gluing MDF to wood because MDF moves equally in all directions. The secret is to design the cabinet properly and the end result if finished properly looks far better than any plywood or MDF veneered - a real piece of fine quality furniture.
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Old 2nd August 2007, 09:25 PM   #8
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Quote:
Originally posted by mandoman
Hardwood will only crack if it has not been seasoned properly, and dried to EMC (equilibrium moisture content) in the environment they are goimg to live, or you do not allow the wood to move as the humidity changes. It is possible to build speaker cabinets from solid wood and have no issues with them, but you must put significant design effort into them so the wood can expand and contract with the weather without becoming stressed.... It is important to know that wood expands and contracts much more across the grain than along the grain.

I,ve preached about EMC, but that's still not enough. A cross grain glued joint will fail eventually; if not completely, then enough for the box surface to go out of alignment and cracks at the glue line to appear. No matter how dry the wood is, it will still move.
Besides, you need knowledge of wood species and a moisture meter to determine moisture content. That's two things not usually found in the average hobby speaker builders toolbox.
If the box is small enough (tiny) and the wood is dry enough, you can make a speaker that might hold it's shape.
Once again, not worth it.

Research: cross-grain joints.
Research: solid wood properties.
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Old 2nd August 2007, 11:53 PM   #9
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You are of course absolutely right about cross grain gluing, that is something I forgot to mention. Don't do it, or if you must do it keep the length of the join short and use a glue that allows some movement.

I agree that in many cases because of the amount of cross grain involved it is impractical to use solid wood (too much movement), but I strongly disagreee with MJL21193 that it is always not worth the effort, particularly with small TL designs which is what I make.

What is quality furniture made of? Solid wood. Do the joins fail and the wood split. Not if it is designed properly and well maintained. Quality furniture is designed to allow for wood movement because no matter what you do the wood is going to move as the humidity changes. You can't stop it moving, and if you do try to stop movement, the wood becomes stressed and something is bound to fail. Either the wood will split or the glue lines will fail. The only difference with speaker boxes is that they need to be airtight, whereas furniture does not. This does make the design a lot more difficult, you can't just glue up a box to the required dimensions and expect it to last like you can with MDF. You also can't use floating panels as in furniture because they are not airtight and will also resonate horribly. However, if you spend the time thinking about how the speaker cabinet is to be put together, paying careful attention to the grain direction, and thinking about how the wood is going to move, and by how much, then the end result is definately worth the effort and extra expense. Not only worth it, but if you choose the right species of timber they will sound better as well. Some woods have much better acoustic qualities than MDF - i,e, stiffer, heavier and better damped. I know because I make musical instruments, and have also made idential speaker cabinets from MDF and solid hardwood. The hardwood boxes have always sounded better and I have have had zero failures so far despite considerable movement of the wood.
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Old 3rd August 2007, 01:07 AM   #10
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Quote:
Originally posted by mandoman

You are of course absolutely right about cross grain gluing, that is something I forgot to mention. Don't do it, or if you must do it keep the length of the join short and use a glue that allows some movement.
You must not do it. Period.


Quote:

I agree that in many cases because of the amount of cross grain involved it is impractical to use solid wood (too much movement), but I strongly disagreee with MJL21193 that it is always not worth the effort,
Either you agree or you disagree. There isn't any middle ground. It is impossible to construct a 6 sided box without cross-grain joints.
As far as me saying it's not worth the effort, that's true. Wafflesomd, the thread starter, is looking or the easy way.
Solid wood isn't it, unless you don't mind temporary speakers

Quote:

What is quality furniture made of? Solid wood. Do the joins fail and the wood split. Not if it is designed properly and well maintained. Quality furniture is designed to allow for wood movement because no matter what you do the wood is going to move as the humidity changes. You can't stop it moving, and if you do try to stop movement, the wood becomes stressed and something is bound to fail. Either the wood will split or the glue lines will fail. The only difference with speaker boxes is that they need to be airtight, whereas furniture does not. This does make the design a lot more difficult, you can't just glue up a box to the required dimensions and expect it to last like you can with MDF. You also can't use floating panels as in furniture because they are not airtight and will also resonate horribly.
I could have wrote this (except for the part about the best furniture being made from solid). Once again, pick a side.

Quote:

Not only worth it, but if you choose the right species of timber they will sound better as well. Some woods have much better acoustic qualities than MDF - i,e, stiffer, heavier and better damped. I know because I make musical instruments, and have also made idential speaker cabinets from MDF and solid hardwood. The hardwood boxes have always sounded better and I have have had zero failures so far despite considerable movement of the wood.

Ah, tune the box like a musical instrument, to resonate at a fixed frequency to reinforce the music in that region. Nice.
Some believe that a vibrating enclosure is a good way to go. I do not.

BTW, very nice mandolins.
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