B&W 800 Series Cabinet Construction ???

[mmoeller]

I have grown to like the looks of the lower section of the B&W 800 series loudspeakers. It made me consider the cabinet construction techniques that they use. After poking around on their website I found some interesting disclosures about the internal bracing.

http://www.bwspeakers.com/index.cfm/fuseaction/products.techfeatures/ObjectID/3A7556CF%2D4779%2D11D4%2DA67F00D0B7473B37

I'm just wondering if anyone here has a guess about the curved sides or baffles. The sides look exceedingly thick. I have seen some of the builds here with curved sides using bendable plywood and the like. Could this be a similar construction with more layers.

I'm not too concerned with the "eyeball" portion. Just really like the look of the thick well finished side panels.

Thanks,
M

[Kal Rubinson]

Yes. They use multiple, damp plies as shown in the 800 series book/catalog.

Kal

[TacoD]

The free B&W 800 introduction dvd has a movie on it where you can see how a big press forms the thick sides.

[JonMarsh]

The free B&W 800 introduction dvd has a movie on it where you can see how a big press forms the thick sides.

Sounds readily adaptable to DIY techniques.... NOT! :W

[mmoeller]

Sounds readily adaptable to DIY techniques.... NOT! :W

What would be a DIY technique to do a multiple curved plywood laminations. B&W mention 38mm or about <1.5" thickness?

I've see guys here do bendable plywood, 2 sheets, on the sides of the curved RS 3-way. Would a similar process be acceptable? Mabey a bending jig of somekind, ribs and straps?? Would it require too much humidity and heat control to be feasible?

[JonMarsh]

Bendable plywood is almost an Oxymoron.

What I have seen done and have done myself is kerf cutting the plywood, clamping around the spars, then filling in the kef cuts, in my case with epoxy. The techniques using thinner cuts must relay on building up a layer with multiple thin sheets.

For now, I'll probably just stick with the easy stuff, like Avalon Klones.

Or no box at all- even easier!

[mmoeller]

Bendable plywood is almost an Oxymoron.

What I have seen done and have done myself is kerf cutting the plywood, clamping around the spars, then filling in the kef cuts, in my case with epoxy. The techniques using thinner cuts must relay on building up a layer with multiple thin sheets.

For now, I'll probably just stick with the easy stuff, like Avalon Klones.

Or no box at all- even easier!

Your probably right. Keep It Simple Stupid rule really should apply here

Interesting topic though. I thought about the thin layers of "Bendable Plywood", and what could be used on a DIY level to laminate them on a form. Mabey a vacumm clamping system. Could almost treat it like veneer, just a bunch of layers. Eh... what do I know.

[ThomasW]

This is why bender-board or wiggle-wood was invented. We have several examples of projects being built with it. 2 layers of ply with the grain running in the same direction. The laminations are put together with a flexible glue.

Prototrax's RS TMWW

https://www.htguide.com/forum/showthread.php?t=15323&page=48

Images not available

Outfitter's Modula MTs

https://www.htguide.com/forum/showthread.php?t=23911

Images not available

[mmoeller]

Would it best to bend the sheets as they are attached to the sides of the bracing, as the pics above? or mabey pre-bend? These sides look like less than 1", would there be a limiting factor for thickness of the laminate?

I know that wood and metal have "memory" or "bend back". Does the flexy stuff exhibit this as much, once laminated? If it was pre-bent would it have to be very accurate to the final dimensions, because it would not bend once laminated? Would it be wise to "over bend" slightly? Would laminate thinckness effect these as well?

[ThomasW]

You can't prebend wiggle-wood, it has no 'memory', so it just flops around.

Yes they laminate up several layers, one at a time. Each layer is 3/8" thick. First layer is usually held on with glue and mechanical fasteners, subsequent layers are just glued on.

Wetting it helps with tight corners. It's pretty easy to work with, a bit on the $pendy side though....

[TacoD]

Or no box at all- even easier!

Except when you want a curved baffle like the Jamo dipoles.

[mmoeller]

You can't prebend wiggle-wood, it has no 'memory', so it just flops around.

I guess I meant "pre-form" or "pre-laminate". Where in you would create the bent lamination prior to afixing to the structure. I would assume that once the "wiggle-wood" was laminated that the wiggle would not wiggle so much any more. Just a question of, would it be easier to create a bent 1.5" lamination as above, or ahead of time on a jig??

[ThomasW]

A zillion years ago when I made something similar, I put the layers on one at a time.

[speedle]

It's nice to know there are other people my age here.

Seriously though, my next set of MT's have GOTTA curve somewhere! 8O