BillFitzmaurice.info

In all my years of DJ and PA I've never run any of my amps in Mono. I've run the signal in mono, but never the actual amplifier. I've also split the amps with tops on one half and subs on the other, but never straight mono. For me I guess my reasoning has been that I didn't want to run two 8 ohm subs parallel (4 ohms) on a mono channel and lose the headroom. I've always been happy just running 8 ohm per side (or 4Ohm when I ran 4 subs) and never saw the need.

I was just curious who does what and maybe reasons why/why not. (aside from the obvious "I only have one sub"...)

Headroom and plenty of power with older amps. With the newer amps not as much. Most of my older amps are 200/400 w per channel versions so running a 600 watt RMS JBL took all she had in MONO. With the MAs no. They are brutally powerful but also very heavy. The newer XTI are nice as they can be run in a variety of configs and really sound nice.Not great on subs but still decent and plenty of balls!

Ron K wrote:Headroom and plenty of power with older amps. With the newer amps not as much. Most of my older amps are 200/400 w per channel versions so running a 600 watt RMS JBL took all she had in MONO.

+1 With the exception of my 1100A, all of my older AB amps are in your ballpark (270 at 8 ohm and 425 at 4ohm) My QSC CX404 is roughly the same power as two of my 600A's but the 600's still seem have more behind them, even with 10+ years on them...but two of them weigh in at 60 pounds + and the QSC is only 21 lbs.

So far I see lots of guys running Mono...Maybe I'll switch it around on the next few events.

If the signal is mono then it really doesn't matter how the amp is configured, you get the same output from all speakers anyway. If the signal is stereo then there may be some benefit from running the subs in mono, but then again you could loose some stereo effects on select tracks doing this. I'm assuming here you are not talking about switching an amp to bridged mono, that will provide 4x the power but will also make the amp run hotter and draw more current, and of course you only have 1 channel instead of 2 to work with.

Yeah.. I'm a bit confused by the question. The sub signal is mono from my crossover, yet the tops are split for right/left. I use 3 channels from 2 PLX2402 amps for driving the 6 subs for 500W peak each, but soft limit to around 300W. The amps aren't run bridge-mono as the 1.9ohm Zmin load would be out-of-spec.

davygrvy wrote:Yeah.. I'm a bit confused by the question.

Me too. I run parallel input, which is a mono signal, but the amp isn't bridged.

So, are we talking about a mono signal

or....

Bridged mono?

conanski wrote:If the signal is mono then it really doesn't matter how the amp is configured, you get the same output from all speakers anyway. If the signal is stereo then there may be some benefit from running the subs in mono, but then again you could loose some stereo effects on select tracks doing this. I'm assuming here you are not talking about switching an amp to bridged mono, that will provide 4x the power but will also make the amp run hotter and draw more current, and of course you only have 1 channel instead of 2 to work with.

I believe he is talking about running an amp in bridge mono and driving a single load.It's commonly done with older amps as they typically only came with 275 or so a side into 8 ohms.If you bridge it you got 400+ sometimes 600 into an 8 ohm load. Running the high powered JBL or EV drivers (600 w RMS) with this kind of power was and still is quite popular with the older amps. There wasn't amps with that kind of power available that were not very expensive and very heavy.FWIW the amp did not run any hotter. Current across the load is current across the load. Running bridge @8 ohms is nearly the same as running stereo at 4 ohm.In fact when you did that you had more amp headroom and often the signal stayed cleaner as you didn't need to run full bore to get the required levels.

In that configuration I always ran bridged for the added power and system headroom for driving single 8 ohm loads (ie"W" bins or cone loaded mid horns).

I've never even bothered with stereo live. Dual mono was the furthest I was ever willing to go. I simply saw no benefit whatsoever live with stereo.I could use dual mono to pan for effects if needed like on some Floyd or especially the stuff done in quad.I would generally not pan anything in the sub region at all. Today it's all single channel mono. I couldn't be bothered with special effects anything beyond some delay on Zeps Whole Lotta Love.

I run parallel input, two channel. Never bridged.

I'm talking purely about running the sub amplifier bridged mono as it relates to the speaker load...not the input signal. I've always run with a mono sub signal.

I've run the signal in mono, but never the actual amplifier.

I'm with Bruce, I've never run my amps Mono bridged, always stereo, parallel, whatever you want to call it...

I can run all 4 of my tubas off of the amp in stereo (two per channel, 5 ohm load) whereas If I run mono I have to run a series/parallel wiring setup to make the amp happy with the impedance.

Tim A wrote:Me too. I run parallel input, which is a mono signal, but the amp isn't bridged.

Me three.

I have three PLX in service. Two 3002, one 1202. A single 3002 handles four T48 at 450w each. Load is only 4 ohms, and the amp is rated for 900w per channel. No sweat. No overheating.

Frankly, I'm not interested in doing FOH work that requires more than four subs and four tops. That is a bigger production than I can trailer.

RubiconProSound wrote: my reasoning has been that I didn't want to run two 8 ohm subs parallel (4 ohms) on a mono channel and lose the headroom.

I wonder if you still are not quite understanding what 'bridged mono" means in terms of a power amplifier. When you switch a 2ch amp to bridged mono it becomes a 1ch amp with 4x the power of a single channel at 8ohms, so you don't loose headroom you gain. As an example an amp that is rated 250w/ch @8 ohms probably does 400w/ch@ 4ohms and 800w bridged mono into 8ohms. You'll notice there is no 4ohm bridged rating, and the reason is the same as why there is no 2ohm stereo rating... the amplifier is not designed for it. The downside with this is you now need 4 amplifiers to power 4 subs and a whole lot more electrical outlets.The upside is you have 6db more output so you could reduce to 2 subs and 2 amps and still have 3db more output than you did with 4 subs on a single amp.(this assumes your subs will produce more output if given more power)