Who's an expert on glue here?

Application - I want to bond layers of Contiboard (white laminated 15mm sheets of chipboard) together for the walls of loudspeakers I'm making. I have 3 layers of contiboard to bond, and my goal is dead, strong and sonically inert panels. This is particularly important for the side panels which are the largest. I will be pulling the layers together with 8mm bolts, exerting some force. One requirement is a flexible lossy bond, and I've used EvoStik for this before - I just hate using the stuff so prefer something less toxic. Don't want anything that dries rigid or goes hard and fractures. I've tried putting self-adhesive roofing strip (black tarry stuff) between the Contiboard, and while this is great for sound deadening, it seeps out particulalry when warm, so the bond isn't really inert once it's been put together. So - what kind of glue can be put on fairly thickly to make a lossy layer, glues Contiboard, and dries solid but rubbery and doesn't seep out of the cracks? Over to you! I have some solvent free Gripfill - is this any good, or does it go brittle when it dries? .

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Reply to
Andy Evans
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I think you would be better off not using contiboard and tracking down some 50mm thick MDF instead.

then you wouldn't need to bond the panels together. problem solved.

RT

Reply to
[news]

Isn't it more normal to use sheets of ply separated by plastic bubble wrap with bolts through the lot at random intervals to hold it all together without standing resonances.

Don't know what your output power is but Contiboard will reflect the sound too much and possibly degrade with the vibration.

Reply to
Mike

Thanks guys so far - the Contiboard decision has been made - it's all cut out and drilled. I found in the past that layers of material with some lossy compound in between sounded good, so I won't be too far out. We have 45mm thickness also with 3 layers. So - what about the adhesive/filler to go between the panels? Silicone sounds like a very good idea - do you mean the stuff that is used for sealing around bathtubs, or any other particular type? Also, what about polyurethene glue?

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Reply to
Andy Evans

No it doesn't !

Reply to
:::Jerry::::

PU glue *could* work, but it would be advisable to roughen the surfaces first, then spread a thin layer on one piece, spreading it all over. Moisten the other piece since this glue requires moisture to cure and it won't get any through contiboard.

You will need clamps to hold the pieces together while it cures and make certain of supporting it over something where the drips won't matter.

Also, do use gloves - e.g. latex ones. If you get it on your hands it will be with you for at least a week.

Frankly, I'd use contact adhesive in a well ventilated space and with a mask fitted with solvent filter.

Reply to
Andy Hall

Silicone would be much too soft to deaden it, bitumen would be nearer the mark. Put it on the inside.

To bond melamine, have had good results with contact adhesive.

You could make it all more rigid with tie bars from one side to the other. Chip is weak stuff, and even 3 layers wont be above bending.

NT

Reply to
bigcat

Why ? It has to be one of the most rubbish speaker enclosure materials ever. Lightweight, minimal damping and minimal stiffness to small deflections. You'd be _much_ better off with MDF, or best of all a cement fibre board like Viroc, Versapanel or Aquapanel (awkward to saw though - the dust destroys machinery).

As an adhesive, then you need to put it on in a thick bead if you want compliance. Even blu-tack will be stiff in shear if you use it in a very thin layer. Probably the best option is a newish(?) flavour of Sikkaflex polyurethane. They've been in the high-end boat and vehicle panel trade for years, but now they're doing an extra-flexible version and selling it into the construction trade. It's called something like "EBT" and Kellaway in Bristol have it. Like all the polyurethanes it's extremely sticky, has a poor shelf life (check tube dates when you buy them) and goes off rapidly once opened.

Reply to
Andy Dingley

Some background information from the BBC R&D labs:

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you want something rubbery between the layers of chipboard, how about using rubber? Aren't rubber sheets available from medical suppliers? Then you could use something like a Hylomar head-gasket aerosol for a thin layer that will stay sticky and not ooze.

What internal volume have you chosen for those poor B110s?

Reply to
Eiron

try using silicone, sticks like sh*t to a blanket!!

Reply to
mark bay

You'd be _much_ better off with MDF, or best of all a cement fibre board like Viroc, Versapanel or Aquapanel (awkward to saw though - the dust destroys machinery).>

there's a guy that recommends Tufnol - do you know about that?

#Tufnol There are two issues of damping and stiffness here. If you make the enclosure stiff enough to resist the drivers newtonian reaction and internal air pressure fluctuations, you shouldn't need excessive damping. The application of enclosure wall damping just adds another resonant mass which while lossy, I suspect works at some frequencies with attendant hysteresis and not at others at all. IMHO damping it won't cure enclosure resonance problems it will just make 'em different! I prefer going for ultra stiff constuction which doesn't obscure microdynamics and bloat bass. Tufnol is great for this, it's a resin/paper composite, it's about as stiff and dense as corian but much easier to use. You can machine it with an ordinary router really well if you're careful. If you dado the joints and bond them with epoxy/ microsphere mix you'll wind up with something far superior to anything you can do with wood. Wilson use this stuff extensively, it seems to have worked quite well for them!

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Reply to
Andy Evans

Epoxy or thick PVA should do the trick. We used to bond sheets of chip with PVA in teh loudspeaker factory.

Clamp up and leave for a few days. I wouldn't use screws and bolts really - tooloaclised - may get voids. Just pile on tos of weight all over. Maybe lay on a flat surface, glue, laminate, and SANDBAG.

IUf you want something gap filing and rubbery, get loads of acrylic decorators caulk. That dries to a sort of yough rubbery consistency. Its not spposed to be an adgesive, but given teh area you have it shold work.

Another possibilitry is expanding foam glue.

Reply to
The Natural Philosopher

The obvious answer is not to use Contiboard which is totally the wrong material. Ordinary chipboard can be bonded as strong as the material itself with PVA wood glue. Or better still, use MDF which is easier to machine - and get a decent finish on for veneering etc afterwards.

However, for simply glueing Contiboard together if you must, use a thixotropic contact adhesive - Evostick make one or Thixofix by Dunlop. This allows easy positioning of the panels before clamping them to set.

Reply to
Dave Plowman (News)

Hmmm..... Interesting idea.

Tufnol (a brand name) is going to be _very_ expensive, and I don't recall ever seeing it in suitable sizes. A similar material called Trespa might be better. It's a phenolic and fabric laminate like Tufnol, but it has a higher content of mineral filler. Chemistry labs use it for bench tops, which is where I get my offcuts.

I'd guess Tufnol is less well-damped than MDF, so you might see some more resonance from it - although this can be avoided by not making the enclosure panels rectangular, so that the panel resonance isn't so strong and well defined.

On the whole though, I think I'd stick with MDF unless I was designing uber-speakers and had an anechoic chamber to test their responses in. It's certainly not worth it for a rectangular box enclosure.

Reply to
Andy Dingley

nail/head.

I think these speakers he's building are for talking about not listening to ;-)

each to their own, I suppose.

RT

Reply to
[news]

It's a hobby, but if you're going to get _that_ serious about materials choice, you should be looking at non-rectangular enclosures.

Reply to
Andy Dingley

I think these speakers he's building are for talking about not listening to ;-)

Not at all! I need some reference speakers because I make valve amps as a hobby. Serious stuff! In fact, the backs of the speakers are sloping so they're not rectangular.

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Reply to
Andy Evans

I've had another suggestion of DAP Alex Plus between layers from a fellow speaker maker. Andy

=== Andy Evans === Visit our Website:-

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Reply to
Andy Evans

And you seriously think you can make 'reference' speakers at your first attempt? ;-) And that it's only down to making a solid cabinet of a suitable shape?

I'd like to say good luck since it's nice to see someone so confident in their own abilities.

And look forward to hearing about how magical they sound on revealing all sorts of things previously unheard. ;-)

You might give some thought as to why few of the recognised best cabinet speakers manage quite well with a 'simple' box?

Reply to
Dave Plowman (News)

and almost every time I've been listening to music through a decent system I've been in the company of others, with a few beers accross me, etc, etc, etc and not once have I been fussed about hearing that elusive harmonic that I couldn't hear before .... too busy enjoying the music and the company.

as I said, the speakers he's building, as serious as he is, are for talking about.

RT

Reply to
[news]

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