PA advice needed

[NHM]

Hi there

As well as playing the low notes I also set up the PA for our band (well, I own it and I'm not sure I trust the others to do it).

I run a pair of 200W 8 ohm speakers for FoH and a pair of 80W 8 ohm Monitors, using two stereo power amps. We use the rig in mono.

I'm trying to reduce the amount of gear I take out to gigs, so have come up with this idea:  just using one power amp, and running the FoH speakers in series from the left channel and the monitor speakers in series from the right. This would have the advantage of increasing the umph of each set of speakers as the load would now be 4 Ohm. The power amp can drive 200W @ 4 ohm so the FoH would be very efficient; I would back off the other channel's output to about 40% so as not to overload the monitors. 

Is this a crazy idea?

 

[Steve Browning]

If that level of power works for you then it works fine.

[jrixn1]

Two 8 ohm speakers in series is 16 ohm - so I think you mean parallel.

Your power amp is 200W at 4ohm per channel - so let's say 120W at 8 ohm.

Previously, each FOH speaker was getting their own channel, so 120W each.

After your change, the two speakers will be sharing a single 200W channel, which is 100W each, which is less than before.

 

[NHM]

I knew there'd be a catch! Thanks for your advice.

[Adethefade]

As mentioned above, daisy-chaining passive speaker cabs is actually connecting them in parallel, which is important to know. I'd say the quickest way to achieve way better performance for the same, or smaller, footprint would be to get a good set of active cabs for FOH use and run your monitors from the existing power amp.

[Woodinblack]

Agreeing with above. If you want to reduce the amount of stuff you are carrying, get a set of active cabs and active monitors. And because you seem to be getting away with very low  power at the moment, they wouldn't have to cost very much either.

[Bassalarky]

A band I play in does exactly what you describe; FOH through channel A and monitors through Channel B of a single power amp.  It has worked fine for several years.  Maybe try it out and see if it is loud enough for you?

One thing to consider with active speakers is the extra mains cables and extensions you might need.

[PaulWarning]

we use a Yamaha EMX 512C mixer amp for FOH and 2 monitors, daisy chain them both from the two channels, not sure what the Wattage is, it says 500 watts a channel but that is 'power' whatever that is, at 4 ohms, 125 watts 'nominal', anyway it's worked ok for about 12 years now, we just use it for vocals and bass drum

[NHM]

Thanks for all the advice.

I like the idea of running FOH from one channel of the power amp and monitors from the other. If the FOH speakers had a different impedance from the monitors, would it harm the amp? Is a stereo amp basically two separate mono amps in the same box?

 

[PaulWarning]

11 minutes ago, NHM said:

Thanks for all the advice.

I like the idea of running FOH from one channel of the power amp and monitors from the other. If the FOH speakers had a different impedance from the monitors, would it harm the amp? Is a stereo amp basically two separate mono amps in the same box?

 

as long as the impedance doesn't drop below what the amp will drive, usually 4 ohms you'll be ok, so if you're daisy chaining the speakers need to be at least 8 ohms, yes, basically, a stereo amp is two mono amps