Building Speakers Using Regular Plywood

kvk

Member
2008-01-25 4:37 pm
I have some large partial sheets of regular old A/C plywood. I think it's either 3/4 or 5/8". I know it's > 1/2".

Just about all the plans I've browsed say birch ply or MDF.

Would it be that bad to use regular plywood?

I'm not to worried about finish. I just want to get some experience without laying out a ton of $ to get started.

I could build a 4.5" design about $100 if I use this old wood. That's not bad for a first time project to see if I have the aptitude for speaker building.
 
Most people avoid builder's grade plywood for speakers because of the inconsistencies in the material. Even AC plywood has voids which makes it an irregular substrate for large scale productions. You may discover one of these voids as you route a driver hole and try to attach the driver to wood that is just not there. For prototyping speakers or learning about the speaker building process, AC plywood is ok, but it you are striving to build a statement speaker, don't waste your time with this lesser material. Baltic Birch plywood is a far more pleasing product to use. Good luck.
 
No, it wouldn't be bad to user regular plywood, ...as long as it is minimum 3/4" thick finish cabinet grade plywood.

The best plywood is Baltic Birch which has 12 layers (roughly) in it.

Second best is standard cabinet grade Birch, mahogany, or oak plywood which has about 8 layers in it.

Worst is common interior or exterior construction grade plywood.

Of course, you can do anything you want. The real question is, are you going to be satisfied with it when you are done?

Steve/bluewizard
 

MJL21193

Disabled Account
2007-03-10 1:20 am
Hi,
Starting here I ran some tests on three different materials, including cheap spruce sheathing.

Not much of a measurable difference.
Obviously, the way the speaker looks in the end will have a lot to do with the material it's made from. Another problem with voids in plywood is that there might be some loose material in it, which will buzz with the box vibrations.
 
kvk said:
I have some large partial sheets of regular old A/C plywood. I think it's either 3/4 or 5/8". I know it's > 1/2".

Just about all the plans I've browsed say birch ply or MDF.

Would it be that bad to use regular plywood?

I'm not to worried about finish. I just want to get some experience without laying out a ton of $ to get started.

I could build a 4.5" design about $100 if I use this old wood. That's not bad for a first time project to see if I have the aptitude for speaker building.

Just use a lot of bracing.
 
I think AC grade will probably work fine. Many wood discussions have come and gone. I've heard plenty of folks mention potential rattles and resonances, but I've yet to hear anyone speak of experiencing them. A couple of guys have even built BIBs (large unsupported panels) with the Home Depot $25 "cabinet grade" ply. In my experience, that stuff has considerably larger and more numerous voids than AC (but that face veneer is nice for the price.) They didn't complain of any troubles. I suppose it's possible that they are making sound at a level too low to isolate as spurious noise but high enough to degrade the sound. I think if you did have an unwanted noise, so long as you could track it down, a dowel or two through the offending region would take care of it.

You've got the wood. Give it a shot and tell us your results. My money says it'll work fine.

pj
 

zacster

Member
2003-12-03 10:49 pm
NYC
I've used cardboard to build test speaker cabinets. You can use anything you want. Since you are really just testing the waters, go ahead with what you have. It'll surprise you how good it will sound, and then you'll want to see how it sounds with better material, then with better drivers, better wire...
 

dfdye

Member
2005-12-04 8:57 pm
USA
If you already have it, there is no harm using it as a starting point! If it ends up having problems, use something different next time (I am partial to MDF myself).

I HAVE experienced rattling/coloration using plywood in sub enclosure, so I stay away now and stick to MDF. Still, if I had a free supply of plywood and wanted to get some experience on the cheap, I wouldn't wait 2 seconds before jumping in with what I had.

David
 
dfdye said:

I HAVE experienced rattling/coloration using plywood in sub enclosure, so I stay away now and stick to MDF. Still, if I had a free supply of plywood and wanted to get some experience on the cheap, I wouldn't wait 2 seconds before jumping in with what I had.

I once used some of the afore mentioned, terrible home depot veneered ply in a little sub. It didn't rattle, but it leaked hugely from the driver hole to the exposed ply edge. That was a funny noise. It's amazing how much air can move through such tiny holes. It's also amazing how long those voids can be. I smeared caulk around the edge of the driver hole and filled the outer edge of the box with wood filler. No problems. It was also very thoroughly braced. Like I said though, that stuff had more/bigger voids than any AC I've seen.

pj
 
I don't make 'statement speakers' by any means and don't even care for finishes much at all.

I've just used some cabvinet grade and can attest to the voides issue. On these panels I've noticed a very this and hardly sandable top layer as well (pretty much paper thin.)

If your remainders are generally straight and you can recut to get really good square then glue ups should be less of a problem (than I had.)

To prevent a lot of glue creep use biscuits or some other spline technique or dado to keep everything lined up. I've had to use butt joints and a hand square and even on a Harvey have had things come out in the 'visually acceptable' range.
 
I like ply.

Stronger than MDF and also lighter. I guess this means it would be more suited to a speaker you are moving around a lot. I built a bass horn recently from 1/2" ply, and I can just lift it... If I used MDF, I imagine it would be a 2 man lift!

MDF would be a better choice if you are going for a permanent install I guess.
 

Bob Brines

Member
2003-01-31 10:11 pm
Just a general comment on plywood:

Plywood always has an odd number of plys. This is because the grain on both faces has to run in the same direction.

!/4" plywood is normally 3-ply, !/2" 5-ply and 3/4" 7 ply. This normally does not include the premium veneer layer on the faces. 3/4" Baltic Birch is normally 13-ply. I use nomally on purpose because variations abound. Normally (again!) the more plys, the less likely there are significant voids.

As for voids, look at the edge of the stack of plywood sheets. What reaches the edge, on average, is an indication of what is going on in the middle of the sheet. BD is going to be like swiss cheese. AC is a lot better, but remember that the grading is on the quality of the face plys. All bets are off on the filler plys.

Bob
 
Bob Brines said:
Just a general comment on plywood:

Plywood always has an odd number of plys. This is because the grain on both faces has to run in the same direction.

Certainly not the case here where 3/4 spruce or fir ply has 6 plies with the 2 in the middle running the same direction. Some say it's no stronger than the 5 ply 5/8 stuff.
 
Bob Brines said:
J
As for voids, look at the edge of the stack of plywood sheets. What reaches the edge, on average, is an indication of what is going on in the middle of the sheet. BD is going to be like swiss cheese. AC is a lot better, but remember that the grading is on the quality of the face plys. All bets are off on the filler plys.

Bob

Look carefully at the edge. At HD, I've seen some sort of filler on the edges of that veneered ply I was mentioning earlier. Honestly. If you glance, it looks nearly void free. If you look close (or cut it open) it is a whole different story.

pj
 
I have built speaker cabinets using BC sanded plywood.

The main drawback that I see is that the plywood is not flat.Makes cutting accurate joints a bit challenging.For a smaller"monkey coffin" it isn't all that bad,but is a pain with a large horn enclosure.

The voids can be filled with bondo and sanded flat.If you want to paint them,you will need to spend a lot of prep time.Cover the whole thing with drywall joint compound and sand smooth.After you do that once,the high priced plywood will seem like a bargain...

Since you already have it,go ahead and use it.