Amp Power Question

Are the drivers 4 ohm or 8ohm? I'd vote for 1 per channel if they are 4ohm.

Hi Sam.
For PA work, you will almost always be wiring bass cones in parallel.
If you have 4 x 8ohm cones, = 2 pairs, then You have 2 x 4ohm loads (cones) to drive, with one standard 2ch amp, not bridged.
4ohms, That's what the load is. No switches or buttons on the amp can change that.
one cone= 8ohm load.
2 cones = 4 ohms
4 cones = 2 ohms, but this is a HEAVY load, and many amps will overheat & crap out with 4 cones per channel, or will not last as long.

As you only need one amp, you can spend double, and get a really good one
If you get one that's capable of driving 2 ohms, then it'll be running at half what it's capable of, so will be really happy, run cooler, and be much more reliable, plus of course, you can always add another cone or two to each channel in the future, or if one amp channel were to fail, you'd be able to wire all 4 cones on to one channel to get you through the gig.


(gonna get shot down here, lol)
Bridging:
Setting the amp for bridge mode links the 2 channels in the amp, so that the 2 channels have one, much higher output, but it can typically only drive 8ohm = one driver.

It's basically a cheap trick to turn a low power 2ch amplifier into one higher output channel, or a way of getting ridiculous wattages into a particularly high power single cone / sub (like in car audio), and I've yet to hear a bridged anp that sounds as good as 'normal' 2ch mode.

I've 'fixed' numerous sound systems, just by un-bridging the amps, and wiring them properly, with a pretty standard 'Wow, what did you do? kind of response.

Don't bother.





Edited by opus jody - 10 June 2022 at 11:25am

Not sure what your paying for the RMX's but could look at an FFA, save a lot of lugging, those RMX's make my back heart just looking at them.

sam012 wrote: fatfreddiescat wrote: Not sure what your paying for the RMX's but could look at an FFA, save a lot of lugging, those RMX's make my back heart just looking at them. Which amp in particular?  The QSC is £1200 inc vat online, but I agree with their weight they'd be a nightmare

opus jody wrote: Bridging: Setting the amp for bridge mode links the 2 channels in the amp, so that the 2 channels have one, much higher output, but it can typically only drive 8ohm = one driver. It's basically a cheap trick to turn a low power 2ch amplifier into one higher output channel, or a way of getting ridiculous wattages into a particularly high power single cone / sub (like in car audio), and I've yet to hear a bridged anp that sounds as good as 'normal' 2ch mode.

wweeeeeeellllll the thing is the Watts aren’t what you’d really want more of. The peak voltage capability is what makes the speaker move and handle the peaks for dynamic, good music. Bridging was / is a way to get an amplifier to be able to handle the exceptional peak voltage demands for unclipped music transients.

The AES75-20222 (M-Noise) peak SPL testing standard has a good example; a loudspeaker with an 8-ohm nominal impedance and AES power rating of 200W covering the midrange (anything above 500Hz) needs 400V of unclipped peak voltage swing to avoid being limited by amplifier capability when playing most music signals.



A Crest Factor of 10 is equivalent to 20dB from RMS to peak.

These numbers aren't just plucked out of thin air either. They're the result of analysing a lot of music files and live concerts.

Edited by toastyghost - 10 June 2022 at 9:19pm

toastyghost wrote: opus jody wrote: Bridging: Setting the amp for bridge mode links the 2 channels in the amp, so that the 2 channels have one, much higher output, but it can typically only drive 8ohm = one driver. It's basically a cheap trick to turn a low power 2ch amplifier into one higher output channel, or a way of getting ridiculous wattages into a particularly high power single cone / sub (like in car audio), and I've yet to hear a bridged anp that sounds as good as 'normal' 2ch mode. wweeeeeeellllll the thing is the Watts aren’t what you’d really want more of. The peak voltage capability is what makes the speaker move and handle the peaks for dynamic, good music. Bridging was / is a way to get an amplifier to be able to handle the exceptional peak voltage demands for unclipped music transients. The AES75-20222 (M-Noise) peak SPL testing standard has a good example; a loudspeaker with an 8-ohm nominal impedance and AES power rating of 200W covering the midrange (anything above 500Hz) needs 400V of unclipped peak voltage swing to avoid being limited by amplifier capability when playing most music signals. A Crest Factor of 10 is equivalent to 20dB from RMS to peak. These numbers aren't just plucked out of thin air either. They're the result of analysing a lot of music files and live concerts.

Edited by Randy Bohannon - 12 June 2022 at 6:30am