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sam012 View Drop Down
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    Posted: 10 June 2022 at 1:06am
I'm debating buying 2 x QSC RMX 4050a but a bit confused on the specs

Running 4 x Void V12 1000

1) Do I run the amps in bridged @ 2600W 8ohm
2) Do I run 1 cab per channel @ 1400W 4ohm

Or is it the same thing?

I know I'm missing fundamental knowledge here, just trying to piece it all together

The reason i'm debating buying the amps above is because they can be bought online without the agro of finding used e.g. a used k10

The reason i'm buying those drivers is for the same reason, they seem to be reasonably available to buy new
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 4:08am
Are the drivers 4 ohm or 8ohm? I'd vote for 1 per channel if they are 4ohm.
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sam012 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sam012 Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 10:43am
8ohm drivers
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Post Options Post Options   Thanks (1) Thanks(1)   Quote opus jody Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 11:22am
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.

So you just need a single 2 channel 4 ohm capable amp (which is pretty much any of them), and with 2 cones on each channel, in parallel (whether its 2 single cabs linked, or a double cab)


As you only need one amp, you can spend double, and get a really good one Big smile
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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 4:29pm
Originally posted by sam012 sam012 wrote:

8ohm drivers
Buy a 4ohm version and wire one driver per channel. Looks like Blue Aran has the B&C 18tbx100 4 ohm on sale.

 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fatfreddiescat Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 6:45pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sam012 Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 7:48pm
Originally posted by fatfreddiescat 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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Father-Francis Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 8:04pm
Originally posted by sam012 sam012 wrote:

Originally posted by fatfreddiescat 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
Look  around you’l Find good amps for good prices, with FFA if I were you , I’d buy used and send it to Dave for a full physical before taking it out . 
Music is the strongest form of magic.(+45 31879997)blakmanpro@gmail.com, foa@sweetboxaudio.dk
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sam012 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sam012 Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 8:15pm
Originally posted by Father-Francis Father-Francis wrote:

Originally posted by sam012 sam012 wrote:

Originally posted by fatfreddiescat 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
Look  around you’l Find good amps for good prices, with FFA if I were you , I’d buy used and send it to Dave for a full physical before taking it out . 

1/3rd of the weight and x2 the power for £600 more*

4050a is 2 x 1400 4r

FFA-6004 is 4 x 1500w 4r


Edited by sam012 - 10 June 2022 at 8:17pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 9:15pm
Originally posted by opus jody 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
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Post Options Post Options   Thanks (0) Thanks(0)   Quote opus jody Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2022 at 11:16pm
Originally posted by sam012 sam012 wrote:


I know I'm missing fundamental knowledge here, just trying to piece it all together



Just keeping it simple.
;)
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Randy Bohannon View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Randy Bohannon Quote  Post ReplyReply Direct Link To This Post Posted: 12 June 2022 at 6:22am
Originally posted by toastyghost toastyghost wrote:

Originally posted by opus jody 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.

I’m trying to work this all out so please bear with me if my questions are silly.

Isn’t it same thing to talk about power and voltage in this context? Given that speaker impedance is a constant, x volts equals y watts doesn’t it or have I missed something?

A crest factor of 20dB on 200w average… that’s 20k isn’t it?!




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