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Old 29th July 2007, 05:56 AM   #1
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Default Which wood?

In return for a few speaker drivers (so that he can himself build a pair of speakers), a local woodworking expert will be building me a pair of speaker cabinets.

While MDF is quite popular, some hardwoods are not so expensive as to be out-of-reach. A local lumberyard has bloodwood pretty cheaply, and I must say, it does look very attractive.

Is this a good or bad choice?
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Old 29th July 2007, 06:09 AM   #2
ostie01 is offline ostie01  Canada
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Hi, be cautious using hard wood because it will crack when there is a change in humidity. Some learned it the hard way.
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Old 29th July 2007, 06:49 AM   #3
OzMikeH is offline OzMikeH  Australia
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Apple ply is nice, use the laminations as a feature.
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Old 29th July 2007, 07:32 AM   #4
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The other option is wood on MDF. Say you want a baffle 1 1/2" thick. Use 3/4" solid timber glued, clamped +/- screwed to 3/4" MDF. Then you wait 24-48 hours for maximum bond strength and do you driver hole cutouts.
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Old 29th July 2007, 07:37 AM   #5
sfreak is offline sfreak  Australia
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Yeah, solid timber glued to hardwood is always a good choice. Mind you I tend to the box whole timber and MDF bar leave the front baffle MDF and give it a good paint gloss black. But hey, I just like it that way. 15mm MDF & 12mm+ hardwood on the outside is always a good compromise in price and strength so to speak so I have found.
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Old 30th July 2007, 01:43 AM   #6
cfbuck is offline cfbuck  Canada
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Ostie01 is quite right, no matter what you do, hardwood will always expand when absorbing moisture with humid conditions and conversely, shrink when it is dry. This occurs with greater range in Canada than perhaps in drier Australia however. Another approach involves allowing the wood baffle to move independent of the mdf cabinet.

A batten can be applied around the outer edge of the cabinet front mdf inner baffle in the species of wood from which the outer baffle will be constructed. This batten can be .75 to 1" wide and .375" thick. I roundover mine with a .375" bit. Construct the baffle with your hardwood so that it will be .25" smaller than the outer dimensions of the box. Then rabbet the back of the hardwood baffle a little less than .375" deep and make the rabbet about .125" wider than the batten.

Click the image to open in full size. Click for larger picture

This will allow the hardwood baffle to drop inside the batten but not quite touch the mdf baffle. But there will be a .125" gap around the baffle which will allow the hardwood to expand and contract. When the driver cutouts and rabbets have been completed, in both the inner and outer baffles, the hardwood baffle is glued to the mdf using green NoMoreNails. This has some flexibility and will allow the baffle to move. This works on a baffle up to 12" wide.

Try to use quartersawn hardwood (it expands and contracts the least). Quartersawn lumber has straight grain lines, not the cathedral pattern that is more common with lumber which is called flatsawn.

Here is a picture of the inset baffle on a speaker that I have done.

Click the image to open in full size.Click for larger picture

In this baffle, the cherry is only .375" thick, but it is glued to a baltic birch ply which is also .375" thick. Although it is glued with PVA, the thinner board should be less prone to break the glue bond with the ply. You can see the ply on the scalloped cutout. But I have used this method with a full .75" hardwood baffle and it still is intact after 3 years of dry winter and humid Great Lake summers.

Finished speaker picture:

Click the image to open in full size.Click for larger picture
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Old 30th July 2007, 02:03 AM   #7
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Using any kind of solid wood for speaker boxes is like rolling dice - you can't predict the results.
Read about it here:
Discussion on what materials to build speakers out of

Expansion and contraction with varying humidity will also be a factor for mounting the drivers (especially large woofers). The wood will shrink or warp around the driver and could potentially twist/distort it's frame.
Worth it? I don't think so.
If you like the look of wood, use plywood or veneer.
If you say you lack the skills needed for good results with veneer or plywood, you'll definitely want to stay away from solid wood.
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Old 30th July 2007, 03:19 AM   #8
cfbuck is offline cfbuck  Canada
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MJL21193, I agree that much more care has to be taken when using solid wood. I understood from the OP that the cabinets were being constructed by a cabinetmaker. So he should have some fundamental knowledge of wood movement.

So my post was just information about another method that has been successfully used by several builders. Here are just two of them:

www.ellisaudio.com

www.salksound.com

Competent woodworkers can build long-lasting speakers with solid wood baffles. IMO the cabinet should still be entirely constructed of mdf or BB and veneers used on the other 5 sides. But for those who appreciate or want the look of solid hardwood, it can still be accomplished by adding a front baffle making the front 1.5" thick and less resonant. The method that is oulined above allows the baffle to move independent of the cabinet so that it is not ripped apart.

The type of wood selected is a variable as is the dryness of the wood. Hardwood used in furniture making is usually kilndried to 6-8% moisture content in our area. This is what I would be aiming for. Check out this website for species info:

http://www.tuktupaddles.com/lumber.htm

However, if a crack or split does occur they can be repaired in various ways, most frequently by filing with a dutchman repair and epoxy filled with the species sawdust.
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Old 30th July 2007, 04:33 AM   #9
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Quote:
Originally posted by cfbuck

The method that is oulined above allows the baffle to move independent of the cabinet so that it is not ripped apart.

The "floating" panel construction is just fine for furniture/cabinet doors, not for speakers. The point I was trying to make is that the driver doesn't expand and contract with the wood. If it is solidly attached to the baffle (which it should be), then you can have a problem.
Another point: having the baffle not glued to the cabinet causes noisey air leaks. Not good.
Read through the thread that I posted. Good points made there.
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Old 30th July 2007, 04:48 AM   #10
ostie01 is offline ostie01  Canada
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Here is an example of what happen on speaker made from solid wood. This happen to my friend

The final product:

http://img53.imageshack.us/img53/849...recracklc4.jpg

A couple of months later:

http://img528.imageshack.us/img528/213/crackxl4.jpg

You can be 99% sure this will always happen.

Jeff
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