Modular 1x12 cabinet

[R.G.]

I'm turning over in my head the possibility of designing a power amp module designed to:
- bolt into a 1x12 cabinet
- get its AC power from its own power cord
- receive preamp-size signal on an input jack
- drive the speaker
- re-drive the signal out to another such unit (or two)
- accept a pull-to-ground signal telling it to turn on
- redrive/send the "on" signal to another unit (or two)
That is, let you use a preamp and one to N power units, so you can take as many as you need to the gig. The current state of the design is that it is a 30W power amp with heat sink on a 12" x 4" plate of aluminum that could bolt onto the back of a cabinet, sealed or not. All the connectors and such are on the mounting plate.

The electronics is easy. The cabinet design is hard - for me at least. I have speculated about making it just 1/4 of a 4x12, or using one of the many 1x12 designs on the web.

Any advice?

[martin manning]

There are powered monitors and PA speakers available already, so what would be different here?

- higher than line level input? (maybe switchable?)
- daisy-chain capability?
- foot switch-able mute?

I assume this would be a clean amp/speaker which would not add color to the sound by itself? This might not do it for everybody, or maybe some EQ or speaker choice could be included.
Maybe a Thiele bass reflex cabinet would be a good idea?

[HeeBGB]

Sounds like fun project. In order to get the powering up (or down for that matter) of the slave units I would say your going to need a multi-conductor cable or separate cables to carry all the signals you need for this. The power command will only need a two conductor but you will also need audio. So that's a minimum of 4 conductor. You might be able to go with a 3 conductor but with audio I am not sure you want common ground with signal wiring and audio.


The easiest way would be to use a PIC with a momentary signal for on/off in each slave unit. So every time the momentary signal hits the input the programming will cycle power. The programming is simple and I can help you with that if you don't already know how to do it.

[R.G.]

There are powered monitors and PA speakers available already, so what would be different here?

Among other things, DIY-ability
Also, designed for guitarists, not monitor/PA, which is somewhat different.
Then there is, as you note:

- higher than line level input? (maybe switchable?)

Yes, that's already part of it

- daisy-chain capability?

More like daisy-tree. One in, more than one out so you could do a cluster simply, and so that failures might not kill all of the sound unless it was in an unfortnate position in the tree.

- foot switch-able mute?

I hadn't thought about that, but it's easy enough to do.

I assume this would be a clean amp/speaker which would not add color to the sound by itself?

That's one option. I'll probably do the first one that way. But it's not necessarily that way. There's more tinkering to do.

This might not do it for everybody, or maybe some EQ or speaker choice could be included.

Electronics... easy.

Maybe a Thiele bass reflex cabinet would be a good idea?

Probably. In fact, an open back, a closed back and a reflex would probably be good things to put in the "design book".

[HeeBGB]

Why marry it to a speaker cab? Why not just a module that has a speaker out and can be used with any speaker available?

[martin manning]

I think it's about minimizing the number of boxes and cables. One could use a small rack-mount preamp and FX, configuration as desired, and one or more of these powered speakers.

[R.G.]

Why marry it to a speaker cab? Why not just a module that has a speaker out and can be used with any speaker available?

Good question.

My reasoning is that a module that's attached to the speaker cab makes setup/tear-down and moving easier, with less thought needed.

The physical design of the amp module is such that it's marry-able to any speaker cab easily enough. That may need more work.

And there is some of this:

I think it's about minimizing the number of boxes and cables. One could use a small rack-mount preamp and FX, configuration as desired, and one or more of these powered speakers.

in the mix, too.

And this is just the kind of thinking I was looking for.

[HeeBGB]

Well thinking in terms of a lot of pro guitarists. They very often have a backline provided to them where they do not bring a speaker cab. Just an amp and whatever guitars they use. Very often they don't even bring an amp. All that is provided by the venue or the promoter. I used to be friendly with a guy who played in several tribute bands and he sometimes would fly to a gig bringing with him only one or two guitars and a little compact 18watt amp head he had built into an army surplus ammo box. The box was virtually indestructible and VERY compact. Anyway he had speaker cab written into his ryder so they would be provided and he didn't have to worry about it.