trying to build an unusual PA

[maestrodave]

Hello!

I'm new to this forum and I joined because I'm in over my head with building a PA system. I am working on a "street opera" to be performed outdoors in the streets of Chicago. All of the PA equipment needs to be battery powered. The musicians are all on mobile platforms built out of deconstructed shopping carts. The chorus of Bearded Ladies are driven around by a forklift.

I have bought a bunch of vintage speaker cabinets, horns, etc from ebay and now I need to refurbish them with new drivers, speakers, etc. They will be mounted on the 15 foot mechanical horse we are building.

I can and will go into more detail but I'm wondering if there is anyone out there that might have a particular interest in this kind of spectacle production and knows more about cobbling together this PA system than I do. I have pictures of everything.

We have experience with using power invertors to run amps from 12v batteries but I'm curious if there is a way to use car stereo amps to drive everything. Thinking that the batteries will last longer! But most car stereo amps I've found are 4 ohms...

Hope to hear from someone soon.

Thanks
Dave

[troystg]

Use efficient horn loaded speakers and class-D amps.

I know the 41hz.com amps can run directly from a 12 volt battery.

http://www.41hz.com/

More specifically the AMP32 has a direct 12VDC input.

[aubergine]

david trotter (aka davey t) over at speakerplans.com has made a serious 12V PA system (nearly fully hornloaded) and is doing a lot of work in that sector. I suggest you talk to him. The 41hz kits apparently draw too much power while 'idle', he says, and uses a different module.

His website is:

speakerporn.com

If that is censored, it is s.p.e.a.k.e.r.p.o.r.n.c.o.m

[john blackburn]

maestrodave

I can't help on the technical side but felt the need to salute you.

Bearded Ladies on a forktruck and a 15 foot mechanical horse?

I just wish I was somewhere near Chicago to see this unfold. Stick at it and PLEASE can we have some photos when it happens?

John

[maestrodave]

Thanks for your responses. I'm exploring speakerplans.com and 41hz.com trying to find someone who can consult me on this setup. Thanks John for the salute! I think (hope) it's going to be quite a spectacle.

Maybe I should take it a piece at a time. I've got 2 Altec 511B multi section horns that I want to mount above the horse. (pictures attached) Is it possible to use 4 ohm drivers on these? Which ones?

[maestrodave]

here's a sketch of the horse and forklift contraption

[troystg]

That would be a fun project to work on... I would love to see pictures or video when it's completed.

Those horns with a decent driver will be >100db / watt.

Forklift? Possible power source for your 12vdc amps?

Put a couple of PA drivers under the horse cart and the horns on top...

The Disney animal kingdom parade had massive 18's under there floats facing down and they sounded pretty good.

[dangus]

A lot of car amps can be bridged, and will then usually deliver double the normal 4 ohm power into an 8 ohm load. Or you can wire two 8 ohm speakers in parallel and get 4 ohms. Or 4 in parallel and get 2 ohms... decent quality car amps will handle 2 ohm loads.

If you need a separate amp for each musician, car amps could be too expensive. There's the SureElectronics digital amps, around $25 from eBay. They'll do about 10 to 15 watts per channel. That's not a lot, but into an efficient "pro" speaker it may be enough. Maybe order one, and see if it does the job.

The Altec 511B have 1.4" throats, right? I think someone makes adapters to use 1" compression drivers. Eminence 1" compression drivers seem like good value.

[john blackburn]

maestrodave

I hope your bearded ladies will be well secured, it gets very wobbly on the forks of a moving truck. It would make an entertaining insurace claim form though, and you could sell videos.

There was an incident a few years ago in England involving a karaoke sing along screening of The Sound of Music.

It is developing a Rocky Horror type following, with the crowd coming in themed dress and joining in with the dances etc. The audience were all giving it total commitment in the final number when a temporary stage collapsed resulting in a good few of the injured being taken to hospital.

I would imagine the sight of loads of blokes dressed as Nuns and Milkmaids being wheeled into the accident department would have raised an eyebrow or two.

John

[maestrodave]

Thanks for the input everyone! I'm still over my head with some of this but I think I've found a local guy at a car stereo installation shop who might take this on. I'll print these out and give them to him. He said he would do some research on this so I hope he can come up with the right parts.

We are doing tests with the forklift to make sure it doesn't topple!

We're also thinking about "pimping out" the forklift with huge subwoofers surrounded by neon lights. Fits the "urban" theme and could be hilarious.