PA cab design

Morning all!

Packing up our gear after a gig last night it became apparent that after several years of abuse our PA cabs really are on their last legs, and that it's not going to be long before they disintegrate completely. As the only woodworker in the band I was volunteered to make some replacements.

Construction wise it's a simple job: make a box of the same dimensions, replicate the internal baffles and route out recesses for the various handles, mounting plates and control panels. The question is what to build them out of.

The current cabs are made of MDF covered with standard black speaker paint. Years of being bashed around, having bear spilled on them and being loaded and unloaded in the rain have taken their toll, and the MDF has blown apart completely in several places. MDF doesn't hold screws very well, so their previous attempts at reinforcing them failed very quickly. Bracing them with metal plates would have helped at one stage, but they're way beyond that now. They also weigh a ton as it is!

My first thought was to use good quality birch ply, which is strong, durable and lighter than MDF. The downside of ply is that the edges don't machine as well as MDF, so a bit of finishing with wood filler and sandpaper would be needed before painting. For this I thought the rubberised truck bed-liner paint like the OEM stuff Demon Tweeks sell would be ideal.

However, a quick scan on a couple of speaker building sites throws up a ton of stuff about cab construction material with convoluted discussions about resonant frequencies, self damping, torsional stiffness and who knows what else. So rather than spend my Sunday trying to make any sense of it all I thought it would just be quicker to see if any of the fine folks on here had any advice they can offer.

So: MDF, plywood, or something else entirely?

I'm in a ply phase - I welded up a desk for my "office" on and put a birch ply top on it. A little bit of oil and the ply looks great.

I found it machines well - you could always put a bevel on the wearing edges if you're concerned about snagging.

The edges would all be rounded over, but you can get a bit of lateral tear-out with ply, leaving voids that I'd have to fill before painting. That's not a problem though.

ours are a bit battered! a few Peavey stickers missing but no cracks,

a bit of ageing is good!

Don't think my old Tandy/radio shack speaker enclosures construction manual still exists but i would in all fairness go with ..

Ebay.co.uk search "brand" empty speaker enclourses/ cabinet before going down the nightmare or construction . Especially for a personal band . It will cost you a lot of time and effort and if any quality issues occur you will not hear the end of it .

It used to be chipboard in the old Ev pa gear i used and replaced a few panels with loft boarding but that was mainly for disco based sounds not for live vocals

I got my 3D printer last week and I'm obsessed with it. You should get a mahoosive one and print them to fit precisely!

How about marine ply?

Thanks for the input guys. I disassembled one of the cabs this evening and it's very basic MDF construction (just butt joints) with the odd bit of plywood reinforcement inside around the handles and the mounting socket. I'll probably make a close-ish copy, but with better joinery!

Well, I built two exact replicas of our PA cabs and have just given them their first few coats of Tuff Cab, which describes itself as a water-based self-crosslinking acrylic paint. However, given the number of drunken whores who invade the stage at our gigs, not to mention our keyboard players habit of spilling beer everywhere (we managed to short out half the Yorkshire Showground a couple of years ago when his pint landed on the mixing desk) I'd like to make my handiwork as band-proof as possible. Any advice on what sort of clear top coat to use? I was thinking of polyurethane, which is hard as nails, but it tends to go yellow after a couple of years. Some sort of lacquer? Or polyacrylic? Any help greatly appreciated, as always...

Chop the keyboard players fingers off so he can't hold a pint!

Problem solved

Chop the keyboard players fingers off so he can't hold a pint!

Problem solved

That would also have the benefit of stopping his cockney-style rendition of 'Country Roads' after he's had a few. I like it!

Great big long spikes should help keep people clear.

Yacht Varnish will do the job.

Just on the off chance that anybody is even remotely interested in my handiwork, here are a few photos from the rebuild of our PA cabs. They've turned out OK!

impressive.

Nice work.

very good!

Thanks guys. Amazing what you can do with a router and a few simple jigs!

Top wood skills!

ooh who doesn't like a bit of routering! top job Mark

ooh who doesn't like a bit of routering! top job Mark

Yup - I'm quite partial to a 3/8" rounding over bit myself. All those years I spent watching Norm Abram's New Yankee Workshop when I should have been studying have finally paid off!

Blast from the past Mark! I used to love that program when I was a kid.

Bet it look crap now though.

Blast from the past Mark! I used to love that program when I was a kid.

Bet it look crap now though.

"Hi, I'm Norm Abram, and today on the New Yankee Workshop we're going to be making our version of some hideous piece of crap that we saw in the Shaker Village Museum that nobody in their right mind would have given house room to in over a hundred years."

All beautifully hand made by machine too.

All beautifully hand made by machine too.

Indeed! Master Carpenter my arse - anyone can use a dovetailing jig! Still it was better than the UK offering: you may be too young to remember Richard Blizzard's Wonderful Wooden Toys...

All beautifully hand made by machine too.

Indeed! Master Carpenter my arse - anyone can use a dovetailing jig! Still it was better than the UK offering: you may be too young to remember Richard Blizzard's Wonderful Wooden Toys...

Oh dear, I remember that.