Building a plywood box - what edge joints?

**Cloth Ears** · 3rd July 2019, 03:31 PM

Hi!

Longtime member, with very few posts - and I've been helped every time! I'm keeping my fingers crossed...

I want to build a 'box' (case) for a bass cabinet (will contain 2 x 15 inch speakers). The design is an old one and is specified (in inches) as 40 x 24 x 14 inches externally, using 3/4" plywood for all the panels. There's a few internal panels for structural strength and to help the sound go low. Obviously, I could treat the finished box with kid gloves and move it very gently all the time - but I'd like to have it built stronger in case I want to sell it.

What joints would you suggest to put the outside of the box together?

Obviously, the front sections can be dado, as the panels containing the speaker drivers are designed to sit back from the front (by an inch). And the internal panels the same. But I'm not sure of the strength if I do all the rest using structural fillets (glue blocks?) all around the other edges and mitred butt joints. I was planning glue and screw wherever possible.

There's no issue with the look, as all visible panels on the inside will be painted black, and the outside will be covered in tolex (flexible, waterproof vinyl). It's just a matter of making it strong enough to fall over and not break.
Attachment 457348

**woodPixel** · 3rd July 2019, 04:35 PM

100% use 18mm MDF with butt joints.

No screws, no nails. Maybe pins to hold it while its clamped, but that it.

I've made HEAPS of speakers for people/enthusiasts/nutters on commish. MDF is absolutely the way to go.

**LanceC** · 3rd July 2019, 07:20 PM

I think the OP may be referring to a bass guitar amplifier cabinet. If that's the case, and it will be gigged, it will need to be able to withstand a significant amount of abuse.

Would MDF but joints still suffice? I know that despite my best intentions my guitar cab gets knocked about a fair amount as a gigging piece of kit.

Lance

**Cloth Ears** · 8th August 2019, 04:23 PM

Originally Posted by LanceC

I think the OP may be referring to a bass guitar amplifier cabinet. If that's the case, and it will be gigged, it will need to be able to withstand a significant amount of abuse.

Would MDF but joints still suffice? I know that despite my best intentions my guitar cab gets knocked about a fair amount as a gigging piece of kit.

Lance

Hi Lance - you're right. MDF would be OK if it wasn't going to move, but it's heavier and easier to damage than ply. So I thought ply should be OK and there's a good shop just down in Mornington.

Originally Posted by woodPixel

100% use 18mm MDF with butt joints.

No screws, no nails. Maybe pins to hold it while its clamped, but that it.

I've made HEAPS of speakers for people/enthusiasts/nutters on commish. MDF is absolutely the way to go.

Hi woodPixel,
I've made my own speakers out of MDF before (although I've generally used 25 or 32mm and then veneered). But this is another kettle of fish, as it needs to be moved (so I'll be adding casters on one bottom edge and handles on the side and top edge) and might be dropped a bit. So I figured the 18mm ply would be about as heavy as I'd want - it's going to be 100x61x35cm and the two speakers are about 7kg each.

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