Speakers in Parallel

[Morpheus]

ok, so when I was setting up some extra speakers for a movie that's going to be shown tomorrow, my brain crapped out on me...
I was wondering, if I have two Renkus-Heinz TRX 121 speakers, 500w@8ohm each being fed by a QSC 404, could I parallel them at the speaker, or would it be best to leave them on seperate channels.




oh, duh.... looking at the QSC page, it says 400w into 4ohms... that would work fine then, yes?

 

[epimetheus]

You should be fine either way; your speakers can handle more power than your amp can put out, at 8 ohms or 4 ohms.

 

[Morpheus]

You should be fine either way; your speakers can handle more power than your amp can put out, at 8 ohms or 4 ohms.

i's not the speakers I'm worried about, it's whether or not the amp will.

And I ran them on two separate channels anyway.

 

[epimetheus]

The amp channels are rated for a 4 ohm load, so you could have done it that way. If you've got a stereo system, I would have ran them on separate channels to maintain the stereo image.

 

[SHARYNF]

In general on a standard amp channel running 4 8 or 16 ohms is fine, with 2 ohms typically not recommended
IF you are running on a bridged channel then you need to be careful since this tends to put the underlying amp channels down to 2 ohms which a lot of amps don't "like"

Sharyn

 

[Morpheus]

Ok, thanks.
Sharyn answered my main question, but you're right epimetheus, the amp is rated for 4 ohms.

Well, i ran them on two channels, but they're only outputting mono source anyway

 

[museav]

If it was a mono source I would have run one speaker per channel and run the source to Channel 1 with the amp set for Parallel mode, which distributes the input to both channels.

I would not run both speakers on one channel, the amp can drive a 4 Ohm load, however most amps will be much happier driving an 8 Ohm load on each channel than driving a 4 Ohm load on one channel and nothing on the other channel.

The other potential advantage to one speaker per channel is that you can adjust each speaker level independently if necessary even with the amp in parallel mode.

 

[j_blinker]

For max power within current and power limits running the speakers in parallel with the amp in bridges mode will deliver approx 400W to each box @ 4ohm as opposed to the max 250W a box running them in any other configuration. If 250W is sufficient then using separate amp channels per box will keep heat at minimum and give best dampning

 

[museav]

For max power within current and power limits running the speakers in parallel with the amp in bridges mode will deliver approx 400W to each box @ 4ohm as opposed to the max 250W a box running them in any other configuration. If 250W is sufficient then using separate amp channels per box will keep heat at minimum and give best dampning

I think you may have misinterpreted the amp specs. The 800W bridge mono mode rating for the QSC CX404 is into an 8 Ohm load (and also at 1Khz rather than broadband) while a 4 Ohm load, which is what the two 8 Ohm speakers in parallel would be, is shown as "not recommended" with bridge mono operation. The two speakers in series would be a 16 Ohm load which would be 500W into two speakers in bride mono mode or the same 250W per speaker as the stereo mode with one speaker per channel. So in this case, bridge mono operation seems to offer no advantages.