BillFitzmaurice.info

Anyone know what the output voltage is on the GX5?

Voltage squared divided by impedance.

Dan30 wrote:Voltage squared divided by impedance.

=watts

Solve for voltage.

63 volts
I first looked up the specs on QSC site, then went and used the calculator to find the answer on this link....
http://www.the12volt.com/ohm/ohmslawcalculators.asp#15

UM.
what about hooking up a multimeter and measuring a sine wave at 50hz or 1khz?
wouldn't that give you something closer to real world measurement?
I think thats what he's asking.

Yes real world thanks

I've never pushed mine more than about 40-50 volts.

Im getting 80v at clip point...

Are you using one black and one red? That voltage is much higher than it should be for that amp.

80 volts would be 1600 watts at 4 ohms.....that's double the stated power. And while I don't doubt that you might get a little more from QSC amps.....it ain't that much.

Yea I have the multimeter hooked up to the output, black to black red to red. Over at the QSC forums they told me 80v is a reasonable clip point for that amp running a sine wave.

He gave me different info about running amps at full attenuation tho.. http://forum.qscservice.com/viewtopic.p ... e30#p21133

ChrisMcCune wrote:He gave me different info about running amps at full attenuation tho.. http://forum.qscservice.com/viewtopic.p ... e30#p21133

Respectfully....he's full of crap. Unless you have a way to keep the volume knobs at EXACTLY the same position ALL the time.....which you don't - then you need to know that they cannot be turned up. By keeping them all the way up - they can never be turned up any louder. By setting your limiter with them in that position, you will never blow your speakers. However, it you set your limiters with the volume knob anywhere but wide open - then your limiter means nothing the moment someone turns the knob up.

You aren't living in the consumer world with these subs. You can't hear when a folded horn is getting too much, because the horn filters out the distortion that would normally tell you to turn 'em down. So, without a hard limiter - you'll have no indication that you are about to blow 'em until they are gone.

Tops are a different story, because you can hear when they are getting too much. However, if you are going to the trouble to limit them, then why sabotage yourself by allowing the limit to be bypassed by turning up the amp?

ChrisMcCune wrote:He gave me different info about running amps at full attenuation tho.. http://forum.qscservice.com/viewtopic.p ... e30#p21133

He is absolutely right about the signal to noise ratio. In car audio/home audio or in a studio where the knobs are set once then forgotten, run your signal as hot as you can and your amps as low as possible to get the lowest noise floor. No question there about his method.

However:

This is pro-audio, where we set up/tear down, transport, let other users play with the dials (either intentionally or inadvertently when a drunk turns into secret invisible sound guy), and having a sound system failure in a middle of a gig ruins everything. Once you lose your subs in the middle of an event that you were paid to provide for, all this will make sense. Even more so if the attendees paid to attend said event. This is your reputation on the line. Accidents happen, knobs get turned, faders slip. By having your amp gains maxed out when the limiter is set, then you (mostly) fool proof your system. The price you pay for an increase of system noise is negligible. Most amplifier system noise isn't in the subwoofer pass band anyways, you won't hear a difference. Tweeters yes, subwoofers never.

Ps: I read something about you worried about always being hard into the limiters at unity on the mixer because your amplifier puts out more than 50 volts and the gains are wide open. That's not true. You take down the subwoofer output gains in your driverack or DSP of choice to prevent that. You can set it so that at unity on your mixer you are just below the limiters kicking in for the subs. The limiters are your last line of defense in case of a mishap, you never want to run into them on purpose.

Bruce Weldy wrote:

ChrisMcCune wrote:He gave me different info about running amps at full attenuation tho.. http://forum.qscservice.com/viewtopic.p ... e30#p21133

Respectfully....he's full of crap. Unless you have a way to keep the volume knobs at EXACTLY the same position ALL the time.....which you don't ....

He's really not wrong Bruce... this is the right way to do it (technically) but you're right that you have to be able to control it. However... these are cheap and do the trick...

http://www.sweetwater.com/store/detail/SEC2

Unless they have a screwdriver and are just super determined to get in there, they're not getting in there. If you're worried about the guy that has a multitool on his belt, buy these:

http://www.sweetwater.com/store/detail/HTX

And get yourself a security screwdriver for your toolbox.

There is ALWAYS a way to get around things without sacrificing performance.

Of course... the best thing to do is simply use amps that are roughly the right size for each speaker. That way you can limit and adjust gain structure in the DSP. If, though, you have to put a way-too-large amp on subs (or bridge a small one so it becomes a way-too-large one) whether permanently or in a pinch... you can do it without worrying.