Type of plywood for THTLP

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dsvensk
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Joined: Thu Apr 19, 2018 2:32 pm

Type of plywood for THTLP

#1 Post by dsvensk »

Hi! I'm about to start building a THTLP as soon as the snow is gone.. And I'm not sure which plywood to get.
It seems baltic Birch is thre prefered choice of material.. I do however live in Sweden and I just can't seem to find anything other than "Birch Plywood", as far as I know it might be from Finish or Swedis birch most likely.
The other I can find is construction strength high qualite Spruce plyood.

Any thoughts on this matter? What should I keep a lookout for?
I did find interior grade birch plywood in 5' by 5' sheets, is that better than the larger exterior plywood?

/ Daniel

EDIT: Also having trouble locating the PL premium glue, are there recommended alternaties?

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Bill Fitzmaurice
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Re: Type of plywood for THTLP

#2 Post by Bill Fitzmaurice »

What do they call English Muffins in England? Muffins.
What do they call French Toast in France? Toast.
I suspect that in the Baltic countries they call Baltic Birch...wait for it...Birch!

I can't help with the PL, but it is used to build houses, and I know they build houses in Sweden, so look for urethane construction adhesive.

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Tom Smit
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Location: Sarnia, Ont. Canada

Re: Type of plywood for THTLP

#3 Post by Tom Smit »

Maybe it's called Russian Birch? The 1/2" (12 or 13mm) is 7 equal plies.There are no voids in the material.
Hopefully, someone on the forum will be able to give you the direction you need to find the materials.
Have you looked through this thread? viewtopic.php?f=14&t=4140
TomS

dsvensk
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Joined: Thu Apr 19, 2018 2:32 pm

Re: Type of plywood for THTLP

#4 Post by dsvensk »

Thanks for replying Bill! I've through my usual suppliers from work, and they don't really differentiate between the plywoods as you guys do. In Sweden there's nothing called Baltic birch plywood, that's why I asked. I used to work as a carpenter and never heard of the stuff! Almost all of birch, plywood or not, sold here is either from Sweden itself or the Balfic countries by default. But we're not a Baltic country... They just sort it into quality grades of surfaces and interior / exterior type. But from your answer and instructions I guess any good quality non veneered plywood is fine...

We do build houses here, but the brands and types of adhesives are a bit different, just wanted to make sure I got the right stuff for the build. Trying to follow the instructions to the letter since they're so specific. If I find a good replacement PU construction adhesive that foams up nicely and bonds well I'll add it to the Europe thread.


Tom, thank you... But I beginning to suspect that it's our interior higher grade birch plywood for furniture that might be closest. Adhesives are a royal pain to find here.. I'm going to give it a try to source it from Germany or my old boss.

Edit. I've decided to give Sikabond T2 I-Cure I try since it's the only PU based construction adhesive that my supplier is carrying. And I'm trying to source 12mm of quality plywood.

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Rune Bivrin
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Location: Stockholm, Sweden

Re: Type of plywood for THTLP

#5 Post by Rune Bivrin »

My preferred source for anything plywood related in Sweden is Calexico Wood (http://www.calexicowood.se/). Great prices, and execllent service. They carry both 2440x1220 mm (8' x 4') and 1525x1525 mm (5' x 5'). They can deliver to your house, or you can pick it up. I happen to have an outlet nearby (Kungens Kurva), so I get it there.
In build order:
O12 with no tweeter.
3 x WedgeHorns.
2 x Jack 10 without tweeters.
2 x DR250.
2 x 16" T39
1 x Tuba 24
2 x SLA Pro (sort of...)

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Rune Bivrin
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Location: Stockholm, Sweden

Re: Type of plywood for THTLP

#6 Post by Rune Bivrin »

I looked at Sikabond-T2 iCure, but I doubt that it's the same stuff as PL Premium. There's no mention of expansion, which is a major benefit of PL Premium when building loudspeakers.

I have ordered PL Premium from Speaker Hardware, and that worked well. I have also used Sikabond-545, which I suspect is similar to Gorilla Glue. It expands and holds up well. The big drawback vs. PL Premium is that it is quite runny, so it's much less forgiving when gluing vertical surfaces.
In build order:
O12 with no tweeter.
3 x WedgeHorns.
2 x Jack 10 without tweeters.
2 x DR250.
2 x 16" T39
1 x Tuba 24
2 x SLA Pro (sort of...)

dsvensk
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Joined: Thu Apr 19, 2018 2:32 pm

Re: Type of plywood for THTLP

#7 Post by dsvensk »

Thank you Rune!
Yes I'm aware of Calexico wood, but their shipping rates are ridiculous. For 3 pieces of plywood I got quoted the equalent of 250 USD.

Regarding the ska 535 I have it at home already but I find it lacking because it's too runny and foam is not strong enough to fill gaps like construction adhesives do. I used it in my last project for gapfilling but found it lacking.

I'll look at speaker hardware, that's a good suggestion! Thank you.
I'll have a talk with my local supplier about high grade plywood...

Bruce Weldy
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Re: Type of plywood for THTLP

#8 Post by Bruce Weldy »

dsvensk wrote: Fri Apr 20, 2018 7:17 am
I'll have a talk with my local supplier about high grade plywood...
The important thing is that it has equal plies. You don't want thicker interior plies with a thin veneer on the outside.

It should look like this...I know it looks weird, but that's several pieces next to each other....you can see the equal plies.
Attachments
OT12 Build 012 small.JPG

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Bill Fitzmaurice
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Re: Type of plywood for THTLP

#9 Post by Bill Fitzmaurice »

Don't be concerned about 'high grade', as that's a cosmetic issue, not structural. For our purposes BB/BB is fine:
http://forestplywood.com/infographics/g ... h-plywood/

dsvensk
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Joined: Thu Apr 19, 2018 2:32 pm

Re: Type of plywood for THTLP

#10 Post by dsvensk »

Bruce Weldy wrote: Fri Apr 20, 2018 8:21 am The important thing is that it has equal plies. You don't want thicker interior plies with a thin veneer on the outside.

It should look like this...I know it looks weird, but that's several pieces next to each other....you can see the equal plies.
Yeah, I read about delamination issues with the veneered plywoods!
I think my supplier found something useful, just the glue left!
Bill Fitzmaurice wrote: Fri Apr 20, 2018 9:43 am Don't be concerned about 'high grade', as that's a cosmetic issue, not structural. For our purposes BB/BB is fine:
http://forestplywood.com/infographics/g ... h-plywood/
Thank you!
Actually BB/BB or BB/B -grade was my aim in visual grade, there's not price difference almost.. This one will not be duratexed however, so the higher B-grade will be welcome for me.
I usually don't use plywood at all so this is a first for me... But I think I finally have found the appropiate grade of plywood from a local supplier now, it's nice even plys, good quality wood and almost void free. They'll get back to me during monday for delivery and pricing.

Don't want to make any rookie mistakes making this thing... Build thread coming as soon as the snow goes away.


EDIT: I've settled on trying the 3M 5005 PU glue, and keep the regular PU-glue for backup.

ketoet
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Location: kortrijk , Belgium

Re: Type of plywood for THTLP

#11 Post by ketoet »

I use structan from the brand rectavit. Very good stuff.
Don't know if that's available in sweden
building BFM speakers isn't a hobby , it's an addiction

1 x THT
1 x autotuba
2 x dr250 melded

2 x wedgehorn 10
2 x tlah

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