Building Your Own PA System

[Standard8]

I'm not sure where to post this, seems like here is a decent enough place, yall seem to know what you are doing.

 

I'm building a PA system for a friend's welding shop, it's a warehouse-type building. He wants music to play on speakers and the ability to page employees "Sanchez, in my office now!" setup.

 

I'm doing this for free, in exchange for some of his services free.

 

I've got 2 watt speakers I demoed from a jobsite a while back. I've got wiring experience, it's what I do for a living (low voltage). I've wired up many office PA's but I've never designed one from scratch, I've just installed what was provided and that's it, the physical labor part of it.

 

 

Basically, I need some guidance.

 

First off: My understanding is that if I've got six (6) 2-watt speakers wired in series or parallel (depending on Ohmage of amp, yet to be determined), then I'll need 12 watts of power, and shouldn't exceed 20 watts. But that's if the volume is turned up all the way. If I get a 50 watt amp, and only need 12 watts, then just don't turn it up past 3 or 4 on the master volume dial... right? Is that a pretty safe-yet-half-assed assumption?

 

Here's the idea in my head now:

 

Uber-cheapo pawn shop stereo receiver with AB switch, or however they want to label it, like "CD-Auxillary 1, Auxillary 2" or whatever.

 

My friend goes from his computer to the Receiver in "input 1" so he can stream NPR, Led Zeppelin, CD's in his computer, whatever, and that plays over the speakers in the shop. Get an el-cheapo microphone from Radio Shack and put that in "input 2".

 

The receiver and microphone will sit at his desk, so he can press/turn from input 1 to input 2, pick up the mic, and say "Sanchez, get your sorry ass into my office" and then switch back to input 1 where the music is playing.

 

I'm pretty sure all of this will work flawlessly.

 

Is there anything about this "design" that I need to take a second look at, or consider in more detail?

 

 

Thanks!!!

[Standard8]

Update: Found a 2 channel receiver with AM/FM, for 10 bucks on CL, a Marantz. RMS power per channel is 35 @ 8 ohms. Not sure what that means, is that 35 watts at 8 ohms?

[agedhorse]

I think you may underestimate the project and how this is generally accomplished. I suggest you read up a little but about industrial/commercial sound applications before promising something you are on your way to not delivering.

[Standard8]

Typically I install a system where there's a phone switch, and it's wired to an amp, and out to speakers, where you pick up the phone and dial a code *367 or something like that, and the switch takes you to the amp, you have the fade-in and fade-out, from music to pa, and back to music.

 

The problem here is this shop doesn't have a phone switch. They are straight out to the pole. So I can't install something with phone codes because there is no switch to differentiate. Sure, I can install a switch, but then we are talking about lots of money. Then I could install some fancy horns w/talkback mics, and a nice big perfect $10,000 system.

 

That's not what this situation is. It's me putting in a simply pa system for a welding shop in exchange for a custom trailer. He's using leftover parts /materials and spare time to make me something, I'm trying to do the same thing.