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Sealing joints on new cabs...

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Old king coles View Drop Down
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    Posted: 09 January 2019 at 9:39am
Morning beautiful people of speakerplans, I'm currently building a complete rig from scratch and just want to get some ideas.
All my joints are butt joints, used wood glue and screws and just wondering if I should run a bead of something around the joints inside the cab? If so what would you recommend? 
Just want to add that I'm chuffed to bits with how they look so far Smile
Will post pics when they're finishedThumbs Up
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MattStolton Quote  Post ReplyReply Direct Link To This Post Posted: 09 January 2019 at 10:47am
Depends on the quality of your joints!

If they are super square, plenty of poly-urethane expanding wood glue, and super good screws, then should be wonderful and air tight. Forever.

Back in reality, any sort of mastic/silicone will do. One that drys and doesn't remain sticky.

Give it plenty of caulk gun action, and then run your (wetted) finger over to really push it into any gap. If you have delicate skin, perhaps use a silicon stick designed for purpose from any DIY/plumbers merchant for pennies!

I cheat. My wood cutting is pretty good and square, and on a good day, I reckon my table saw is good to 1/10mm per m (but I did spend days trueing it up, with run out gauges and cutting 5 strips off a rotated square of wood and Vernier each end to see how true a cut was! I am that sad. The 1/10mm was deliberately added to "help" minimise kickback risk a little). However, I still use the wood glues that work like expanding foams to fill any shonky-ness. Good grip on wood, and fills with quite a hard foam to fix any "issues".

Titebond on anything else less gas tight (say braceing), and use enough glue so it squeezes out of joint. Wet finger, run over PVA oozing out, forms a nice bead line of seal.

If your going OTT, use a batten (glued/screwed) to strengthen the joint, and then mastic its gaps to the sides.

I am (painfully slowly) knocking up some new studio monitor cabs (only MDF, and more for shitz and giggles), and actually just did Tightbond PVA and biscuits. Plenty of glue oozed out of joint, as it was clamped up, and the wet finger made a pleasing bead along all joints. I also cheated, and picked up a set of glue applicators, to decant the big bottles of Tightbond into, so there is a roller applicator, nozzle, biscuit nozzle etc, which really helps get plenty of glue, in an even consistent layer. You don't want voids in the glue? And then clamps. Lots and lots of clamps. Sash clamps. G Cramps. F Clamps. Ratchet clamps. Ratchet straps. More Clamps. Big chocks of wood to spread clamp pressure evenly over joint. More clamps...Few brads just to make sure....Then do not touch anything for 24 hours.

See how Uncle Norm (Abram) does it.
Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
"Sparkius metiretur vestra" - "Meter Your Mains"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bob4 Quote  Post ReplyReply Direct Link To This Post Posted: 09 January 2019 at 10:51am
Unless you have actual, visible gaps, plenty of wood glue should be enough. If you get moderate amounts of glue squeeze out for the length of the whole joint you are good! If you have the skill and tools, rebated joints would give you added strength and tightness. It is possible to do rebates with hand tools, when you get the hang of it it is fun, although takes a bit longer.

Squareness of the edges would be another concern. To get bad edges straight and square, i have found hand planes to be highly useful. It can also be used to true up several panels (sides or back and front of a cabinet for example) to perfectly equal dimensions, so that you get a perfectly square box. Preferably get one number 4 jack plane, and a big jointer plane (the bigher the plane, the more straight it will cut).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote njw Quote  Post ReplyReply Direct Link To This Post Posted: 09 January 2019 at 7:47pm
My cab building skills and tools have become vastly better over the years (still far from an expert!) but I still run a bead of caulking around all internal joints when building a cab, just seems 'right' to me.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote I-shen Soundboy Quote  Post ReplyReply Direct Link To This Post Posted: 09 January 2019 at 11:30pm
I'll just add:  Don't use silicone sealant if at all possible, it gasses off something atrocious as it cures, which won't do your driver chassis any favours.
Acrylic sealant is way good enough, cheaper, safer quicker and washes with water so you can safely run your finger down it for that perfect curve (not that anyone else will see it mind).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote freddymendez Quote  Post ReplyReply Direct Link To This Post Posted: 10 January 2019 at 7:59am
Edit :)

Edited by freddymendez - 10 January 2019 at 11:20am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MattStolton Quote  Post ReplyReply Direct Link To This Post Posted: 10 January 2019 at 11:39am
Originally posted by I-shen Soundboy I-shen Soundboy wrote:

I'll just add:  Don't use silicone sealant if at all possible, it gasses off something atrocious as it cures, which won't do your driver chassis any favours.
Acrylic sealant is way good enough, cheaper, safer quicker and washes with water so you can safely run your finger down it for that perfect curve (not that anyone else will see it mind).


IIRC, as "silicon sealant" cures, it emits ethanoic/acetic acid fumes. A.K.A. Vinegar.

Hardly dangerous, just get a bag of chips, and leave them in the ports.

Alternatively, leave a bowl of water in base of cab during curing, and any fumes (which are hydrophilic - likes water) will tend to dissolve into water, forming a weak acetic acid (vinegar) solution. Remove bowl before loading!

Could, in extreme cases, corrode metal, but it is hardly a strong acid, and with a quick blow out of cab before loading, once sealant has fully cured, will go away.

No harm in going with something else if you prefer less smell, I quite like it!
Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
"Sparkius metiretur vestra" - "Meter Your Mains"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Old king coles Quote  Post ReplyReply Direct Link To This Post Posted: 10 January 2019 at 5:37pm
Thanks for the help chaps, much appreciated 
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