help setting up live sound, someone elses gear, confusion

[bryan_kilco]

Hey all. Here's my deal. My band set up a show at a local bar. There is a PA there. What they have is:

-a tiny mixer, 4 channel, only 2 XLR inputs. (we're going to need more inputs)
-2 power amps. 1 of which feeds 2 bigger 2x12 verticle with horns, and 1 which feeds 2 regular 1x12 speakers.

I'm trying to take our PA head (powered Behringer Europower something-or-other) and run maybe the preamp out into their power amp(s).

Here's my confusion: the power amp that feeds the bigger 2x12 speakers as the connections like on a home stereo (don't know the name of the connectors) where you wrap the wire around the poll and screw the "cap" on.

The other power amp has regular 8 ohm 1/4" outs.

These 2 amps are not daisy chained, they are receiving separate feeds from their mixer. (main outs and ctrl room something out....setup for DJing)

I'm not exactly sure how much power these amps can push, or if we'll even need all they have. We'll only need 2-3 vocal mics and kick mic and/or trigger.

Should I just take our PA head, and run Preamp Out into just one of these power amps? Or can we do something simple such as run RCA cables from our PA to their tiny mixer?

Also - do the same rules apply with a PA about having a load connected at all times?

Just don't want to break anything that isn't ours and I don't normally work with live sound and poweramps, etc.

 

[arv_foh]

It's hard to give help without you even knowing the exact models of gear you are working with (your powered PA head).

You should sub the stereo L/R UNPOWERED output (assuming there is one) into 2 channels on the mixer that is already there. Then you don't have to mess with any of the other house equipment. A power amplifier does not have to have a load attached at all times.

However..

Those amps are 150w a channel and are meant for studio monitors and home theaters. They are probably not gonna get very loud and your gig is gonna sound like shit.

You should find the budget and hire a local production company to bring a decent PA system out to this show. Your fans deserve better!

 

[Sloan]

If the amps can't produce at least twice at what the speakers show for average power then you have a very high chance of ruining the speakers.

It might be best to bring your own gear

 

[if6was9]

Doesn't look like much of a system, but you often see bars that dabble in music with mismatched setups. Chances are if they run metal gigs there already with that system that the speakers are wrecked anyway.

Probably be best to bring in your own system if you've got some half decent tops to go with your powered desk.

 

[bryan_kilco]

We're going to bring everything we have. Our PA setup is just minimal. We're also borrowing another mixer from a friend.

Yeah they dont really do metal gigs at this place often at all, this setup is for DJs.

Thanks for the input guys. I'll let you know how it turns out.

 

[bryan_kilco]

Well fuck me sideways.

Our bassist brought a (more powerful) power amp and bigger mixer. Claims "I got this", sets shit up.

By the end of the first bands set, our speakers were friend. =/ Thankfully there were extras at the venue and we threw our powered PA head in and the rest of the show went fine. Really should have just stuck with our own setup from the get-go, but everyone suddenly has great ideas when its time for shows and I just stay away from shit because when you have 4 motherfuckers trying to tweak a mixing board shit gets frustrating.

Thanks for your input guys. Really sucks we are out probably $600 worth of speakers, but it could be worse. We were told that there are internal fuses for crossover inside the speaker an that it could be as simple as the fuses fried.

 

[if6was9]

Well fuck me sideways.

Our bassist brought a (more powerful) power amp and bigger mixer. Claims "I got this", sets shit up.

By the end of the first bands set, our speakers were friend. =/ Thankfully there were extras at the venue and we threw our powered PA head in and the rest of the show went fine. Really should have just stuck with our own setup from the get-go, but everyone suddenly has great ideas when its time for shows and I just stay away from shit because when you have 4 motherfuckers trying to tweak a mixing board shit gets frustrating.

Thanks for your input guys. Really sucks we are out probably $600 worth of speakers, but it could be worse. We were told that there are internal fuses for crossover inside the speaker an that it could be as simple as the fuses fried.

The bigger amp and desk should have been a good thing. It's very common practise to run speakers with an amp often 2X the power it's rated at. It most likely broke because it was ran into the red, any speaker will die a quick death if you do this to it.

 

[bryan_kilco]

Yeah. Opened one of them up the other day. No fuse. Limiter bulb...?!? Never looked inside one of these before. Our bassist seems to know a bit more about it.

Either way, the horns work but the "subs" don't. We can't see anything fried/broken. Multimeter test still left me scratching my head. I think, once the sound started getting thinner (during first bands set), our vocalist was up there turning knobs and I bet he just sent too much power from the amp to the speakers. Oh well. Live and learn. I just stayed out of the whole situation because I can't stand how everyone wants to be turning knobs and messing with stuff.

Me: slight EQ tweaks to get rid of some mic feedback
Vocalist: steps in and starts changing stuff, meanwhile checking the mic right next to the speaker instead of out on stage

*facepalm*

 

[arv_foh]

That's what you get for not listening, you could have hired a good PA for 300 bucks and now you're out double that

 

[Sloan]

If they use the light bulb limiter, they will blow just like a fuse. It's funny the horns work, that's usually what the fuse/limiter protects first. You can see if the voice coil of the woofer is fucked by pressing the speaker cone in/out just like it would do if it were operating. If it's smooth and no problems and you get a correct ohm reading, then it's probably ok. Check the crossover for any signs of burning etc...


Post specs for the speakers and the amps you run them with. I'm guessing they were underpowered.

 

[bryan_kilco]

That's what you get for not listening, you could have hired a good PA for 300 bucks and now you're out double that

We didn't exactly have time for that and each band only made $88 that night so it really wouldn't have been worth it (except for the fact that we fried our speakers) but, hey, I let someone else in charge and this is what happens. There was no reason to even do it that way in the first place since we were only running (2) 1x12s with horns for vocals and we could have safely used our own setup and been fine the entire night. Someone claimed they knew what they were doing and I just baked off the situation as, I said, there were basically 4 people all trying to fuck with this setup at once and it was silly.

Sloan - checked the bulb with a multimeter and it is fine. The speakers move when pushed and there are no signs of anything burnt on the board. There's a little transformer in there too....maybe that could be the culprit?

Not sure of exact specs right now, but our normal setup is Behringer powered head with "matching" speakers.

The setup we used at the gig was a single poweramp (unsure brand) which I think he said put out 750 watts per channel, but was not cranked at all. Our speakers have a peak of 1,000w or 250 continuous. My guess is overpowered them. Everything seemed fine for the first half hour or so.....then boom, treble-y distorted quiet.

Either way, it sucks we ruined perfectly good speakers, but oh well. It's just cheapie Behringer stuff anyway.

 

[Sloan]

750 watts per channel, but was not cranked at all

That is a problem. Run amps full blast. If everything is matched up correctly, it will generally be too loud or feeding back before you fry anything due to over powering. Under powering will force you to run everything too high, creating clipping, which creates too much work for a speaker and fries it or overheats something else.

750w into a 250w continuous should be generally ok as long as it's 750w at the same resistance (ohm).

http://www.crownaudio.com/how_much_power.htm