What is the best adhesive / Glue for speaker boxes?

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oatmeal769

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Joined 2009
#1
As happens with giant forums like this, a search for a common word or string will bury you in responses. I'm sorry if this has been asked a million times.

I've heard that PVA like Titebond is more than you'll ever need, Gorilla Glue because it expands, Marine Epoxy because it's the strongest, etc...

Well, which is best for a subwoofer which will be made from Baltic birch plywood, coated with a polyurea shell and live its life on the road?
 
#3
Make sure you have good joint fitment and standard PVA will be way more than good enough. Urethane glues like Gorilla aren't actually that strong, and are probably more popular for hiding fabrication sins than anything else.
 
#5
Titebond vs Gorilla glue

How good is your woodworking? When you have poor tooling or infrequently assemble projects, the Gorilla glue can ensure that your sub is airtight. If you are a fine woodworker and your joints are tight, then the titebond is easier and probably better all around. Your tools and plywood warpage will dictate the glue needed in your situation. In other words, Got Voids? if yes. the ape is your friend.
Richard
 
#7
If you can clamp the joints tight while it dries, ordinary white glue is more than strong enough for speaker boxes. I don't see any advantage to using yellow glues like Titebond on anything that will not be exposed to weather. Be careful with polyurethane glues like gorilla glue, they expand as they cure and can push joints apart if they aren't clamped or secured with fastenings. For my last set of boxes, I experimented with a quick setting 2 part epoxy using a caulking gun and mixing nozzles. Very messy if you are not careful, but it worked great. I was able to glue up the boxes and start finishing the same day. More expensive than ordinary wood glue.
 
#8
I fall into the lousy-carpenter category. That's why I like space filling glues. Epoxy has some work time, doesn't need clamping, has little smell, fills space nicely, takes paint, sands, not too expensive for speaker boxes, and does more. For cross-bracing (essential for nearly all boxes) I simply used light-weight steel electric conduit tubes, anchored with a lump of epoxy all around the two ends. What could be easier?

B.
 
#11
box size, weight?

joint design?

just about any would benefit from internal corner brace/'glue blocks'

for lots of moving/travel I'd add external metal corner protectors

acoustically a sub box could be light, thinner ply than you might expect as long as you raise the panel resonance above the pass band with internal center-to-center cross bracing - 'damping bracing' would be the best

last few pages of Sealed enclosure -- golden ratio? looks ast some references, I'd search for more 'damping bracing' comments in the forums, gedlee in particular
 
#12
jcx said:
… acoustically a sub box could be light, thinner ply than you might expect as long as you raise the panel resonance above the pass band with internal center-to-center cross bracing…
Click to expand...

Indeed, we built my subbs with well braced 15mm plywood (and mounted push-push woofers for active vibration cancelation). You could pick the box up with one hand, after adding the woofers it was really a 2 man lift.

dave
 
#14
bentoronto said:
I fall into the lousy-carpenter category. That's why I like space filling glues. Epoxy has some work time, doesn't need clamping, has little smell, fills space nicely, takes paint, sands, not too expensive for speaker boxes, and does more. For cross-bracing (essential for nearly all boxes) I simply used light-weight steel electric conduit tubes, anchored with a lump of epoxy all around the two ends. What could be easier?

B.
Click to expand...
Liquid nails, fills voids, super strong AND can be cleaned up with paint thinner when dry. (unlike gorilla) I've ripped up plywood glued to floor joists, practically impossible. Use the oil base, standard or heavy duty, not the type made for foam.
 
#15
I just use a good brand PVA glue.

I found I had to be very accurate with saw cuts so I didn't get voids where the glue wouldn't bridge.

I get the basic sheet cut up by the wood supplier leaving me with just minor cuts to do myself. Even then I am extremely careful to draw a straight line , be at the right angle and be very careful with the circular saw along the line. Even if it means taking a little extra time over the cut.

As always measure 3 times and cut once.
 
#16
I am a pretty good (being modest) wooddorker and have a good shop (Powermatic TS with jigs and all setup well etc) and but large designs like subs are HARD to get square/tight joints. Tight joints being defined IMO as not being able to pass a piece of paper through. Now, if you're better than me by all means use wood glue. I prefer PL adhesive since it expands. All this being said, IMO adequate bracing is far more important than choice of glue.
 
#19
nigelwright7557 said:
The glue should be stronger than the wood.

With new glue I always do a test sticking two pieces together. I let it dry then try to pull it apart. If the wood gives first then the glue is good.
Click to expand...

Oh, Elmer's Wood Glue is definitely stronger than the wood I use it to stick together.

A re-run of all the crap that happened to me with my last build:

1. Designed the box around the use of 18mm MDF, only to discover what I had on hand was 21mm MDF. Luckily I found this out before cutting wood! Easily fixed via the optimizing featured that I built into the Excel workbook describing the design.

​2. Used a 30cm ruler for measurements. Some of the panels had to be 45cm wide. no problem - 30cm + 15cm = 45cm, right? So, I made the marks, went inside for a drink, came back outside, drew the cut lines where I'd marked the wood, cut the wood, then discovered that I'd made the cutline on the 30cm mark, not the 45cm mark. And of course there was no more wood left that was at least 45 cm wide!
​
3. I decided to just cut some 15cm wide lengths, and join them onto the panels that were cut 15cm short. Than I stuck them together with wood glue, and clamped them, making sure that the panels were lined up as closely as possible, and left it overnight to dry.
​
4. I went to continue work the next day on the build, only to discover that I'd somehow managed to stick the wrong panels together.
​
5. I decided to break the panels apart and confirmed in the process that yes, it's actually true that wood glue is stronger than the wood. I ended up fracturing both panels.
​
6. I fixed the broken panels (wood-glue, filler, clamps and sanding) and turned my attention to the doing the rest of the box, gluing the back panel and the internal separator panel into place, and left overnight to dry.
​
7. I wake up next morning, check to see what the work I did looks like, and find out that I glued the separator panel in the wrong location (glued it below the guide line, not above). Sigh. BTW, remember what I said about the wood glue being stronger than the wood? More damaged panels and more repair work required. Well, at least this happened on the inside of the enclosure, so less visible...

8. I finally finish the damned box, and it looks somewhat passable. I sanded it down smooth, gave it a few coats of DIY sealant, then placed it outside to let the sunlight properly dry it out before I commenced painting, and went inside to get a drink. Of course rain immediately started falling. Remember when I said I was using MDF? I managed to grab the box before it got too wet, but still the MDF sucked up some of that water like a sponge, even with several layers of sealant applied to it. Still, it didn't look like any damage was done, so I left it overnight to dry.

​9. The next morning, I examined the box and found that there was minor swelling along one edge of the box. I'm not sure if was there before the rainstorm or arrived afterwards, but it needed to be fixed. Another day lost spent sanding, clamping and sealing.

​10. One week after doing a build that should have taken one day, the box is finally finished. I screw the driver into it and perform the linearity tests, only to have the subwoofer give a loud pop and suddenly go silent during the -3dB test. Goddam it, did I blow the driver? I took it out and tested it, and it tested fine, phew! I screwed it back into the box, ran the test, and still no sound from the subwoofer. Strange. I took the driver out, tested it again and it tested fine. So this time I screwed it back into the box while it was playing a signal. The signal cut off as I started screwing the screw directly opposite where the terminals for the driver are located. Turns out that when the driver cutout is 21mm deep, that's just enough to squeeze the driver's push terminals in, and the blinking connection cables were falling out. Chamfering the driver cutout where its terminals would be located solved the problem.

Other than the above, this build was a pretty easy one .
 
#20
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