BillFitzmaurice.info

Hi all, I'm new to the forum and attempting to get involved in the DIY madness.

I'm having trouble locating wood for my first project building 2 THT LPs. I've searched my area and called a few woodworking shops with no luck finding Baltic Birch in 4x8 sheets. The closest I've come is some Columbia Forest Products 1/2 in. x 4 ft. x 8 ft. PureBond Birch Plywood at a big box store. My worry with this is the glue is touted as being Soy-based PureBond adhesive which sounds amazing but I'm sure never been tested with a 15" driver hammering away in its core.

Link to the plywood I found: https://www.homedepot.com/p/Columbia-Fo ... /100020218

Any suggestions on other types of hardwood I can look for? Anyone know if the PureBond adhesive would be ok?

nightfx wrote: ↑Mon Jan 25, 2021 7:43 pm Hi all, I'm new to the forum and attempting to get involved in the DIY madness.

I'm having trouble locating wood for my first project building 2 THT LPs. I've searched my area and called a few woodworking shops with no luck finding Baltic Birch in 4x8 sheets. The closest I've come is some Columbia Forest Products 1/2 in. x 4 ft. x 8 ft. PureBond Birch Plywood at a big box store. My worry with this is the glue is touted as being Soy-based PureBond adhesive which sounds amazing but I'm sure never been tested with a 15" driver hammering away in its core.

Link to the plywood I found: https://www.homedepot.com/p/Columbia-Fo ... /100020218

Any suggestions on other types of hardwood I can look for? Anyone know if the PureBond adhesive would be ok?

Welcome to the party. I'm Seth.

Baltic birch usually comes in 5'x5' sheets. My local specialty lumber yard has both, 4x8 and 5x5, but the 4x8's are like $90 a sheet, where the 5x5's are about $35 a sheet... about half the cost per square foot.

Where are you located?

nightfx wrote: ↑Mon Jan 25, 2021 7:43 pm Link to the plywood I found: https://www.homedepot.com/p/Columbia-Fo ... /100020218

This makes it unsuited to speaker cabinets: Decorative top and bottom veneers, measuring approximately 1/42 in. thick.
You want equal thickness plies, with no veneer. Nine ply 1/2" birch has 1/20 inch thick plies. You don't have to use birch, but you do need to have at least 5 equal thickness plies.

Hi Bill and Seth, thank you so much for your replies!

I'll email a few more lumber yards today to see if they have some equivalent with 5 equal thickness plies. I'm in Richmond VA, there are a few lumber stores around so I'll keep trying!! Thanks.

I also assume MDF for this application is out of the question...

I was considering Sonotubes with 18" drivers but from what I've read about the THT with a 15" driver and less power I can get even more output. The footprint will be larger but this is a dedicated room so it's fine.

nightfx wrote: ↑Tue Jan 26, 2021 9:02 amI also assume MDF for this application is out of the question...

Correct. While MDF can be used (and has been used indeed) it does have quite some downsides. Dust from cutting is a lot more harmful than dust from birch ply. Corners are not easy to finish nicely and remain fragile. Screws pull out with relative ease and the resulting damage is ugly. MDF loves to soak up moisture and then basically just falls apart. It is heavy. The last point is more important for pro sound as cabs get hauled around a lot.

As an alternative you can see if you can find decent poplar ply. While not as nice to work with and dents a bit easier compared to birch, it is better than MDF. Same constraints as birch: at least five plies of equal thickness, no thin veneer outer layer.

Poplar is rare in the US. Besides, it's not the species that matters, it's the plies. I've used five ply fir and it works fine, but it has a rough texture.

I'll just add that if you have never worked with baltic birch, you will be surprised at how nice it is. Smooth finish, cuts clean, doesn't warp as much as some other options.
Once you try it, it is hard to work with inferior materials and you realize the value of a little more effort to obtain it. Once you put the work into building something, you will be glad you used quality wood.

nightfx wrote: ↑Tue Jan 26, 2021 9:02 am Hi Bill and Seth, thank you so much for your replies!

I'll email a few more lumber yards today to see if they have some equivalent with 5 equal thickness plies. I'm in Richmond VA, there are a few lumber stores around so I'll keep trying!! Thanks.

I also assume MDF for this application is out of the question...

I was considering Sonotubes with 18" drivers but from what I've read about the THT with a 15" driver and less power I can get even more output. The footprint will be larger but this is a dedicated room so it's fine.

It doesn't have to be a premium ply. Premium ply is nice to work with and there's usually much fewer voids throughout, especially evident on the edges where a cut has been made.
Depending on how much finishing work you're willing to do, filling and sanding knots and voids, you can use standard siding ply. Again, just make sure it's 5 ply. I've used Douglas Fir CDX siding ply for 2 cabs (Tall Auto Tuba and T39), and will use it again for the next 4 T39's. If you can find ACX, it has a better finish. The store I got the CDX from, had ACX, but it was only 4 ply. So, I went with the 5 ply CDX. The Douglas Fir is lighter than Birch, but if you're not moving it around like a mobile system the slight weight difference won't really be of any real benefit. Might only be about 10-ish pounds difference for a complete cab.

I looked really hard to find Poplar ply out here in CA. All the distributors said that the market dried up when the trade market tariffs were modified. Guess it became more expensive to import than the market would bear. I did find one place that specialized in yacht interiors that had it (they use it to keep weight down), but they wanted something like $135 per 4x8 sheet. I needed 12 sheets, so I went with the CDX, which weighs about the same and was only $20-ish a sheet.

If you want to use birch and can only find it in a 5x5 sheet, there's instructions at the end of the plans (bottom of page 19, top of 20) to join sheets of ply to get you to your 71½" dimension.

CP Johnson Lumber in Elkwood has 5x5 ($40) and 4x8 ($65) Baltic Birch. Looks to be about a little over an hours drive from Richmond area.

Wow, again thanks for the responses; this is extremely helpful and Seth, thank you so much for going out of your way and searching my area!! I was calling places that were around 30m or so away.

If the filling/sanding is only for cosmetics it wouldn't really matter to me; these are going behind the screen and I'm just going to spray them black. If it's something to do with structural or sound integrity I'm just not skilled enough yet.

I did also inquire about the ACX but no one seems to have it at 15/32". Going through all this, if I travel to the Birch destination I'm buying a lot of it - o0o0 - I have TLAHs to build next.

nightfx wrote: ↑Tue Jan 26, 2021 7:43 pm if I travel to the Birch destination I'm buying a lot of it - o0o0 - I have TLAHs to build next.

It can't be said enough.......remember that you want Baltic Birch, not just birch. Birch plywood will be cabinet grade with a thin veneer.

Some places call it Finnish or Russian birch also. Hate for you to drive an hour and ask for the wrong stuff once you get there.

and there's Chinese Baltic Birch too. Like the others said, just make sure it has multiple (7 or 9) equal plies and no pretty veneer layer on the outside. Awesome stuff to work with!

himhimself wrote: ↑Wed Jan 27, 2021 10:38 am and there's Chinese Baltic Birch too. Like the others said, just make sure it has multiple (7 or 9) equal plies and no pretty veneer layer on the outside. Awesome stuff to work with!

Good point.......Stay away from the Chinese stuff....

The link for the place I found says it's Baltic Birch, Made in Russia, and the 4x8 option is noted as being Marine Grade.

Save $4 a sheet when you buy 3 or more sheets.

The place deals in exotic woods for the fine craftsman. I'd be highly surprised if it was the the thin outter veneer stuff.

Speaking of which, when I first suaght out Baltic Birch for one of my builds, several places called it Veneer plywood. If you hear that term, don't be put off... I'm fairly certain it refers to it being comprised of "veneer" plies, thinner than standard ply would have. But, still verify the ply count to be sure.

Also, the plies should be more or less equal thickness, all the stuff I've seen, the outter layers are still a smidge thinner than the inner layers.

nightfx wrote: ↑Tue Jan 26, 2021 7:43 pm ..Seth, thank you so much for going out of your way and searching my area!! I was calling places that were around 30m or so away.

I called a bunch of places in Richmond too, and asked each if they could point me in the direction of someone who might have it... ended up full circle, where they would recommend someone I'd already called. Then I did a Google search for "Richmond, VA Baltic Birch Plywood" and came across a thread in a different forum where someone else was looking for the same thing in Richmond. Someone in that thread mentioned the place I linked to. Seems like a good solid lead.

If the filling/sanding is only for cosmetics it wouldn't really matter to me; these are going behind the screen and I'm just going to spray them black. If it's something to do with structural or sound integrity I'm just not skilled enough yet.

Re: finish work for CDX sheathing ply... For the most part, it's cosmetic. Although, voids within the ply that become apparent after a cut can cause a weak spot on the edge of a cab if not dealt with. Though, it's easy enough to just force some adhesive (PL) in the void with a scraper/putty knife/piece of cardboard and sand it flush once it's cured.

Full disclosure on the CDX option; It's rare (I've never had an issue), but aparantly sometimes the lower grade ply can have a void within the plies, mid sheet, where a loose piece will rattle around and can be heard as a buzzing in the cab. If it's on a panel that's accessable from outside the cab, you can solve an issue like this by using a hose to listen to the cab panels to determined the area the noise is coming from. Drill a few holes in that area and force adhesive into the holes, in an effort to secure whatever is loose. Again, it's rare. But, there have been a few reports of buzzing panels over the last 5-10 years. If it's coming from a panel that's not easily accessed, it gets a little trickier to solve. But, nothing is impossible.

I'd estimate less than 5% chance of having an issue like that though. Again, I've never experienced it firsthand.