Limiter threshold level

frank4d

I used to keep my post-crossover limiter thresholds set at 10db. This worked with the three QSC PLX amps I used since they all had the same input sensitivity (mid's the highest level and set to 0 db in the crossover).

I have recently added a QSC PL6 II to my rack replacing the PLX3402 (more mid power needed to drive my SRX722's). The input sensitivity to this amp is quite a bit higher and requires a good +5db more than the PLX3402 needed to obtain the same volume from the DR. Because of the newly acquired large spread between the mid settings in the DR crossover, I lowered the subs and highs a bit and raised the mids to +4db in gain.

All that said, do I now need to advance all the post-crossover limiter thresholds by +4db as well? (from 10db to 14db?) I am not sure if crossover gain directly relates to the limiter gain.

Thanks in advance...

Gadget

How about setting the amp up with no speakers attached, set the desired limiter factors except threshold, then send signal enough to just get the amp to clip, and then lower the threshold till you have determined the threshold point that stops the clipping.
Or better yet, set up the gain structure properly so that you KNOW that the amps and mixer and DR are all on the same page ...lower the amps gain below clipping and use the mixers meters to KNOW when the system has exhausted it's resources, then use the above method for the limiters to set "OOPS" protection for the speakers...your far less likely to damage the speakers with this method than to drive the system into the limiters and raise the average power of the amps that will cause voice coil heating...
Gadget

frank4d

I'll give it a try, thanks.

As far as my last question, does increased crossover gain effect post-crossover threshold?

Dennis

frank4d wrote:

I'll give it a try, thanks.

As far as my last question, does increased crossover gain effect post-crossover threshold?

I believe it does but Gadget's method still holds because he is using the amp clip lite as a limit indicator. What impedance are you running the amp at?

Dennis

frank4d

HF: Stereo @ 8ohm
Mids: Stereo @ 8ohm
Subs: Bridged Mono @ 4ohm

Dennis

I believe the original discussion was specifically about your mids. The PL6II specs indicate it has a voltage gain of 32dB and puts out 1300W into 8 Ohms measured at 1K. If you put a 1K tone through your mids(speakers not connected) and increase volume until you see clip lites you should be able to meter about 144Volts across the + and - speaker connectors. Try adjusting the limiter to limit at about 142Volts for pretty much full amplifier power. This is the same concept as Gadget posted...but it is measured from a different point. No matter where you set the DR output level of your mids, you have to adjust your limiter to limit at 142Volts. If you don't feel like you need a full 1300W, you can limit sooner.

Dennis