So, this is pretty out there, and there's probably very few people out there that would know but...well, basically, the speaker cab I use at the minute is one that I've built myself, but I've decided I want to rebuild it as it's in a bit of a shit state. And so my mate goes "Why not build it out of aluminium?" and initially I was like "Naw", but then I started thinking about stuff like Travis Bean guitars, which a made out of aluminium and I started thinking...maybe it's not such a bad idea? Would anyone have any idea about whether or not this would be good?
Its an interesting idea for sure. And i like it. But i think you'd probably have to have a wooden frame with an aluminium shell. Fully aluminium construction might not be as good at dispersing unwanted rattles from speaker as wood, so it might sound a little different. But really, i have no idea. Im sure you'd have to be careful with your wiring though...
I think the basic requirement for speaker cabinet shell material is that it has to be stiff, so if you used, say, 20mm thick aluminium sheet, it just might work.
Aye, I was considering around 20mm. Mounting the speakers on MDF (there's no way I'm attempting to put circular holes in some 20mm aluminium ). I imagine I wouldn't need to worry too much about internal bracing, the aluminium should be much stronger than the wood. The main thing that worries me (really, really, really worries me) is making an enclosure out of conductive material. Some kind of short could be real bad I imagine, anyone have any ideas on how you would make it safe?
...and yeah...done a bit of searching, aluminium plate of that thickness is really, really expensive. Back to wood I guess...
Make the strength in the wood, have it on the outside and have the inside all aluminium. You can use thinner material that way.
As for shorts, good question, although very highly unlikely.
Speaker outputs are almost always ALWAYS wired like this: a basic output transformer has two wires on the 'out'. One side is the 'speaker hot', the other side is connected to the chassis (ie earthed)
Even on 'multi-out' amps with 4, 8, 16 ohm, the rule still applies - one wire of the output transformer (secondary) is earthed.
So naturally, one side of every speaker coil will be earthed. Just get it right and you'll be fine.
The whole reason plywood is used for speaker cabs is because the layers prevent resonance in the structure. Proper wood is used when making instruments because the regular structure allows for resonance, giving the instrument a 'tone'. Speaker designers design cabinets in specific shapes so the frequency response matches the application by varying internal volume, porting, shape etc.
With aluminium, it will resonate at a specific frequency (and it's harmonics) as it has a regular pattern. It may sound nice, it my not, I've never used an aluminium cab.
My advice would be the same as Leifs, to make a wooden frame and screw the aluminium panels to it, this way you can use thinner sheets of aluminium. Attach your speakers to 18mm ply unless you fancy cutting 12" holes in the aluminium which would have to be thicker than the other panels to support the drivers.
Dickinson Amps as used by Matt Bellamy
They use 5mm Au sheet