Cabinet Plywood

[GregS]

I built a 2 x 12 sealed back non-resonant cabinet from 3/4" Douglas Fir plywood from Lowes. I think the cabinet sounds pretty good. However, I keep seeing everywhere that birch (particularly baltic birch) is the building material of choice and many seem to think it has the best sound. Many manufactures advertise using Birch in their cabinets and it seems to be almost a standard.

So what is the deal with it? Is it simply that the wood is easier to work with if you're making finger joints or dovetail joints? What leads me to think this is that it also appears to be the choice wood for head cabinets where it will obviously have no affect on the sound.

The only way I can see it affecting tone in a solid non-resonant speaker cabinet is if the reflective or absorptive properties of the wood are favourable some how and in turn affect how the speaker resonates itself. I would think that the physical construction of the plywood and whether it has voids or not would be more significant in this regard than the wood type though.

The problem I have with just simply using birch if in doubt is finding a source for it. The home improvement stores don't have birch plywood that is birch all the way through. The core is something else. Also I expect that it would be significantly more expensive if I was able to find it.

I have read all the threads in here concerning cabinet woods but have not found conclusive answers to my particular question (i.e. will birch plywood sound significantly different in a non-resonant sealed cabinet or is it mostly hype?)

Thanks,

Greg

[Kazooman]

Birch plywood (often called Baltic Birch) is used for applications where very high quality and stability is desired. The big difference between birch plywood and regular construction grades of plywood is in the quality of the wood used and (most importantly) the number of laminations. It's the combination of many laminations and quality wood without any defects or voids that gives birch ply its superior quality. One place where this comes into play is in the dovetail or finger joints. The outer laminations of regular plywood may flake or break off, but the birch plywood gives perfect results. For a given size piece I think the birch ply would be denser, stronger, and more resistant to twisting or distorting, but I do not have any references to quote on this. It is just my experience of many years of woodworking.

I rooted around in the shop and found some 1/2" birch plywood. Here's a photo of it with a piece of regular 3/4" plywood on top. The difference is readily apparent.



Of course, both types of plywood will be found in various grades of quality. In my experience, even the cheapest birch plywood is better than any regular construction grade material. I am not certain just how these properties would affect the sound of a cabinet, but when I built a 2 X 12 cabinet with Celestion Vintage 30's in it I chose to use good Baltic birch I purchased at a lumber yard about 45 miles from home.

[GregS]

Thanks a lot Kazooman for that information. That clears that up for me.

BTW your cabinet looks great!

Greg

[guitarmike2107]

other than easy to work with and much better quality, it must also be "void free" Birch ply wood or any type void free high grade plywood. if its not void free you could end up with buzzes.

if you can't find good birch ply you would probably be better building the cab with MDF type wood than using construction grade plywood.

[GregS]

I found a source of Birch plywood close by. Much better quality wood than what I had been using.

Greg

[Bill Moore]

I envy you guys who are able to buy decent wood for your projects! There is nothing local to me, and to ship anything in costs a fortune. I too have used a lot of the MDF because it is here. Just really heavy to move!

[Diablo]

For folks in the Chicago area, look up Owl Hardwood. Great selection of wood for building cabinets, including baltic birch plywood. I was very frustrated looking at wood at the big box stores like Lowes.

[redelephant]

Be ware there are several grades of birch plywood as well. What we want more than furniture grade outsides is that each ply layer is the same quality and the glue used is good to go. So called 'marine grade' and even better 'aircraft grade' is guarantied to have high quality wood in all layers. Check out Bruynzeel's mahogany plywood if ya really want something special to work with, but it is REALLY expencive, I think the 1/2" is about 135bucks a sheet! I have used it once, and each layer is guarantied to be equal quality, and it really is nice, reall light weight too.
If you dont have a local store and must order anyways, I'd check out Pilot Supplies, Avionics, and Homebuilt Aircraft Parts from Aircraft Spruce and Specialty Co..

[roughcut studios]

plywood source

Boulter Plywood in Somerville, Mass. has an extensive inventory of all types of plywood, including the fancy hardwood veneer faced, and fancy marine grades of mahogany from a couple of different makers. Expect to pay dearly for the good stuff, and shipping?...forget it!