Super baltic birch

[Illusus]

I just aquired a truck-load of some very neat, unused baltic birch ply. It is made for Mercedes transport truck flooring. I plan on doing a little research on this stuff and post the results here.

I played around with it a bit yesterday and this eveing this is what I know so far:

The quality of this material is higher than I've ever seen in any plywood(more on this when I post some pictures tomorrow)

The sheets have about 3'x5'' of useable area per panel ( these are pre-fab with holes drlled here and there, the 3'x5' section is with out holes). I ripped some of these to make the 3'x5' 'clean' panels and I also ended up with a lot of useable 12"x 24" sections.

The plys are much thinner than in standard Baltic Birch.

It is extremely strong and stiff for it's thickness of 7mm. strength test in a different thread.

Due to the mere 7mm thickness, the panels are quite flexy over a large area, therefore not so good for speakers with large panels, very well suited for bookshelf or small monitor type cabinets.

The face is covered with a very hard, smooth resin, the back with the same resin but it is textured and has some type of fine abrasive mixed in with it. This was made to be reversable depending on the type of duty the truck was to serve. The colour is an almost black cherry that is actually quite appealing, a few people have seen it in my shop and asked if I could make cabinetry out of it for them - based on the finish alone.

You can hit it with a hammer and not damage the finish. There are limits, of course.

Wood glue, contact cement and weldbond would not adhere well to the finish. I tried laminating two of these yesterday, I tried sanding, face to face, back to back...not so good ...but I did make a small (5"x5") cube with bevel(mitre) joints all around, so the contact areas were edge to edge, I assembled it with wood glue and a couple hours later I was throwing it at the floor trying to break it apart, it withstood the rough treatment admirably.

Although the standard type glues did not work well on the resined sides, plain clear silicone worked with acceptable results, and I had great results with some industrial adhesives like Sika-Flex.

Since I have the capability for making repeatable, accurate cuts quickly, I'm thinking of putting together some flat packs for a DiyAudio Reference monitor kit... if we can come up with a design we can agree on. These would be cheap because the wood cost me a symbolic amount, I have enough for at least fifty pairs of cabinets if kept small by design. The total cost would be composed of a symbolic something for my time and effort, a donation to the forum, and shipping...I could probably keep it at around $20 a pair plus ship, give or take.

Also, if anyone interested in helping with this project wants to check the material, I'll send out samples if you cover shipping.

[planet10]

looks like your experiments preclude any kind of lamination other than contrained layer...

put a label on an oversize letter scrap and mail it... we'll see how it survives a Canada Post torture test.

How small a cab do you think? WR125 size (7 litres) or 3" TB size <1litre?

dave

[Illusus]

I'll send one out to you tonight,Dave, you tell me how it looks when it gets there.

7L ...of the top of my head...8 x 12.5 x 5, that's about the max I'd go strictly because beyond 8x12 the panel may get too flexy without bracing. I have a 7x11 panel in my hands now, I can very slightly bend it using my knee as the fulcrum... about 1mm deflection , end to end. When I knock on it the resonace f is very high for a piece of material this size, sounds like a block of hardwood. There is also the option of using a dowel to brace the large panels, not the most effective, but works.

I think if we keep a speaker kit really cheap there should be no excuse for many forum members to own a reference set up, we already have the cheap, repeatable gainclone, maybe we can settle on a cheap, readily available source too.
This way at least a number of us can have the same, good, resolute system that can be used to compare anything from recordings to cables to whatever tweaks we want to try...the only difference will be our ears. That's the dream, anyway. This has been mentioned on this and other forums many times, but I haven't seen it ever go through. Maybe DiyAudio can be the first.

[Illusus]

Oh, If we kept the size at ~1L (3"tb or Hi-Vi) it would be pretty cool IMO. This way I could keep very close tolerances and use a drill press for the driver hole (I have some big forstner bits), overall cost would be less, ie. the shipping would be cheap, I could satisfy a lot more demand (multichannel anyone?), the drivers are cheaper.

Keep in mind, we're not out to build the best loudspeaker in the world, but a good sounding one that we can all use to test ideas...surely, they'll have to sound good and look proffesional but tha main goal is to have a reference, of course, purchases for non-reference use will be accepted.

I have some generic 3"ers kicking around, I'll build a pair of little boxes tonight and take some pictures, just so everybody can have an idea of what the finished design may look like.

[Mr Teal]

Out of curiousity, where are you located in the Prairies, Illusus?

[Illusus]

Saskatoon.

[Mr Teal]

Hey, that's cool. I'm from Saskatoon, though I just moved to Red Deer in February. I was just back last week trying to knock one of my tires off in the Spadina potholes. :P

[Illusus]

Hehe, yeah, the roads are awful this year...Main St. is 4x4 access only

I shipped a sample panel to David just now. They accepted it without packaging, $2.45 lettermail.

I'm off to the shop to knock-up( ) a couple little enclosures, I'll post results in a couple hours. The cool thing about mitre joints is that no clamping will be necessary for assembly, just tape and glue for perfect joinery.

[planet10]

Originally posted by Illusus
7L ...of the top of my head...8 x 12.5 x 5,

A golden ratio box would be ~ 19x12x31 cm inside -- sounds a bit big for me....

dave

[planet10]

Originally posted by Illusus
Oh, If we kept the size at ~1L (3"tb or Hi-Vi) it would be pretty cool IMO. This way I could keep very close tolerances and use a drill press for the driver hole (I have some big forstner bits), overall cost would be less, ie. the shipping would be cheap, I could satisfy a lot more demand (multichannel anyone?), the drivers are cheaper.

I think that is more reasonable... ~6x10x16 cm inside (ignoring the space the driver takes up).

The Auratone Tim was playing with is another candidate. The FE8xs might also be a consideration... also the Adire AV3. We should copile a list. A simple sealed cabinet wouldn't give the lowest bass, but the most consistent given driver-to-driver variation.

i think good but affordable is a laudable goal.

These would also make good 'puter speakers.

If we can choose one driver and an ameniable driver vendor a volume discount can probably be negotiated.

dave