Project Tang Band W8-1772 / Brines Accoustics TT-2000

[Ludomaniac]

Hi!

So I've just started on my new project - building a pair of full range speakers. Since I'm quite new to DIY, at least when it comes to speakerbuilding I would appreciate some input and help from you guys with a lot more experience than myself.

I got the drivers yesterday, and now I'm currently studying the plans that Mr Bob Brines sent me a couple of days ago. First thing that comes to my mind is that he suggests using 3/4 inch (19mm) MDF. Is there anything that would improve the construction like if I use birch plywood instead? My local dealer can get me that, but only in 18mm and 22mm thickness...

I'm looking forward to hear your oppinion about this, thanks

[planet10]

18 or 22 would do. 18mm ply is equivalent to something like 30mm MDF in terms of stiffness. 22 would decidely be a yeoman build.

dave

[David Whistance]

If your plans are anything like the LT-2000 ones, Bob specifies MDF lined with a plaster/cement board. He also specifies a ply alternative, I think of 18mm lined with 6mm. It is best to email him or read through the posts on the Brines Acousitcs forum where this has been discussed several times for various enclosures.

David Whistance

[Bob Brines]

Here's the deal:

All of my plans were drawn on the assumption of 3/4" material with a 1/4" liner. If you omit the liner, the cabinet volume changes. So.... You need to line the cabinet with something 1/4" thick (6mm) is close enough.

I tired of fighting the MDF/BB battle. I am using 3/4" quality plywood for my commercial products. I line them with 1/4" plywood attached with an elastic adhesive -- "Liquid Nails" in my case. This provides some constrained layer damping and takes up the required volume. I remain convinced tha 3/4" MDF/cement board is a good combination.

Cabinet grade plywood can be had in 3/4" thickness. BB, most MDF and any Chinese plywood will be 18mm. Using 18mm material instead of 3/4" will mean that the overlapping panels will stand proud by ~1mm. That's fine. you can then run a router trim bit or a plane over the edges and be assured that the resulting surface will be flat.

Bob

[mor2bz]

I wish Liquid nails was not so bloody toxic; it makes me positively sick.
a good adhesive, I'm sure.

[chrisb]

Bob would be the one to verify this, but IIRC from some old fabrication photos, the internal liner panels (whether cement board or plywood) are not "structural" - so perhaps a latex (not silicone) based caulking would work just as well as solvent based construction adhesive? For that matter there are low VOC "green" construction / sub-floor adhesives available.

[chrisb]

Originally Posted by chrisb

Bob would be the one to verify this, but IIRC from some old fabrication photos, the internal liner panels (whether cement board or plywood) are not "structural" - so perhaps a latex (not silicone) based caulking would work just as well as solvent based construction adhesive? For that matter there are low VOC "green" construction / sub-floor adhesives available.

:

www.Titebond.com

[Bob Brines]

Originally Posted by chrisb

Bob would be the one to verify this, but IIRC from some old fabrication photos, the internal liner panels (whether cement board or plywood) are not "structural" - so perhaps a latex (not silicone) based caulking would work just as well as solvent based construction adhesive? For that matter there are low VOC "green" construction / sub-floor adhesives available.

Right, and the technique is HERE. The idea is that the two layers, the MDF and the cement board, resonate at different frequencies. Since the layers are joined by an elastic bond, at least in theory, the energy is dissipated as heat in the elastic layer. I'm not going to guarantee that it woks 100% in practice, but that's the theory. I beleive that the MDF/cement board cabinets I built are as about as dead (i.e. pass not sound though the cabinet walls) and is reasonable without exotic techniques.

As to whether there is an alternate to Liquid Nails: Probably. I use this product because it is cheap, works well and as I work in a well ventilated area, fumes are not an issue. I typically use silicon adhesive to glue on supra-baffles. I have not tried latex caulk, but it might work. I might just try that with my next demo box. If anyone else tries that, let me know.

Bob