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I found the right plywood but its too thin can i glue them together to make them more tihick. Iam thinking that i will glue 4 pieces together. So 4 layers of plywood.

Obviously, that's not the right plywood if you need to glue it together.

So, start at the beginning. What are you building? What plywood do you have? How thick is it? How many plies? Does it have a thin veneer?

Take a picture of it.

You can, but that doesn’t mean you should. I have a lot of 3/8” bb that I will laminate together when I need something thicker. But not big sheets. I’d agree with Bruce that you probably don’t have the right ply for what you’re doing. Especially if what you have has a thin veneer face.

thank you
i coudnt find baltic birch in the right thickness in Slovakia.
So i will probably go with birch plywood i found the right thickness with 5 layers.
I want to ask if more layers equals better sound or 5 layers is just ok?

holzboss wrote: ↑Mon Apr 27, 2020 8:42 am thank you
i coudnt find baltic birch in the right thickness in Slovakia.
So i will probably go with birch plywood i found the right thickness with 5 layers.
I want to ask if more layers equals better sound or 5 layers is just ok?

you want equal thickness in each layer regardless of the number of plies. What you don't want is cabinet grade plywood as it has very thin veneer on each side and will separate under high pressures - especially in subs. What cabs are you building?

Tuba 60

Bruce Weldy wrote: ↑Mon Apr 27, 2020 9:08 am

you want equal thickness in each layer regardless of the number of plies. What you don't want is cabinet grade plywood as it has very thin veneer on each side and will separate under high pressures - especially in subs. What cabs are you building?

Here they have 18mm Radiata labeled as cabinet grade, it's a beautiful product that's nearly void free and visually looks much like Baltic Birch. All equal thickness ply's and no thin vernier. It's really too bad it's too thick and they wont/can't order 12mm for me. Point is, plywood that's labeled "cabinet grade" isn't always universally inappropriate. Maybe it's a regional difference in terminology or something.

holzboss wrote: ↑Mon Apr 27, 2020 8:42 am
I want to ask if more layers equals better sound or 5 layers is just ok?

As the plans state, at least 5 Equal thickness ply's without any thin vernier.

In many cases, thin vernier will delaminate, pull off, and separate... so anything that's glued to the vernier will fall off too, causing buzzes and rattles in a cab... and a cab that slowly falls apart.

Cabinet grade usually refers to having a thin outer veneer that takes a finish. It means kitchen cabinet, not speaker cabinet.

I think this gave me the answer to the question I was about to ask.Before this pandemic hit I bought some 1/8” and 1/4” plywood for DR250’s.By the time I needed the 1/4” for the throat horn(?) it would not bend at all.I measured and they had given me 3/8” instead of 1/4” and they were closed because of Covid.When they reopened I returned the wood and got the right size,now I’m not comfortable using that wood,wetting it and using clamps,I know it will pull away,not doing that again.I even cut a piece in the opposite direction to make sure I had the right bending axis.I guess they sold me cabinet grade because it seems to have the thin veneer outer layers,unlike my 1/2” BB I bought from Ohio with all even layers

The DR250 hasn't used 1/4" plywood for bent pieces since before the last revision in 2012. Back when it did use 1/4" the plans specifically stated that it must be 3 plies. More than 3 plies will not bend to a small enough radius.

Thats what the problem is then,im using the plans from 2009 (i wanna keep all my DR's uniform) which states 1/4" for the mouth horn sheaths and the update states to use 1/8".I take it that i can use 1/8" ? I have a whole sheet of that curled up.I still have a problem with the wood i was sold,if 1/4" should only be 3 plies and they sold me a 5 ply then they didnt give me what i paid for.Thanks Bill.

1/4" BB and some other species can be more than 3 ply. That's why the plans were specific that it had to be 3 ply.

Can I use 1/8” for the horn sheaths with the pre 2012 plans or do I have to have 1/4” ? It seems that 1/4” 3 ply is not at any of the places I buy from.

You may, if it's for PA used with subs. I wouldn't otherwise. It's hard to believe that no one has 3 ply 1/4", as that's the least expensive grade. Finding 1/4" with more than three plies should you need it is the usual problem.

I just called Toledo plywood and the lady said she had 5 ply but wasn’t sure about 3 ply,she’s gonna check with their buyer and call me back.I will be using these with subs,three DR’s per side.