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[Yosi Melamed]

I've read allot of articles about limiting and still didn't understand how to do this, I want to run a couple of SRX728s of one IT8000 in parallel mono, that would give a peak power of 6000W, which suits the 728s fine, but it would also give 4000W continuous which is too much. How can I configure the system so the speakers will not get more then they can handle continuously without sacrifying the desired peak power?

[Ryan Lantzy]

I've read allot of articles about limiting and still didn't understand how to do this, I want to run a couple of SRX728s of one IT8000 in parallel mono, that would give a peak power of 6000W, which suits the 728s fine, but it would also give 4000W continuous which is too much. How can I configure the system so the speakers will not get more then they can handle continuously without sacrifying the desired peak power?

I'm pretty sure the ITech series from Crown has RMS limiting.  I believe you would just use system architect to configure that and the DSP in the amp takes care of the rest.

[Yosi Melamed]

I'm pretty sure the ITech series from Crown has RMS limiting.  I believe you would just use system architect to configure that and the DSP in the amp takes care of the rest.

RMS limiting would not let the amp make more power then the value you limited it to which means bye bye headroom. My logic points me to set the attack time to be high, so a bit of headroom would remain for the duration of the attack time. I don't know if this is the method to use and that's why I posted.

[Ivan Beaver]

I've read allot of articles about limiting and still didn't understand how to do this, I want to run a couple of SRX728s of one IT8000 in parallel mono, that would give a peak power of 6000W, which suits the 728s fine, but it would also give 4000W continuous which is too much. How can I configure the system so the speakers will not get more then they can handle continuously without sacrifying the desired peak power?

There are a couple of "definitions of "continuous".

There is what is on the spec sheet-which is generally  meant to be continuous music type signals.

But what is YOUR music signal?  If you are talking about long sinewave type tones (typical in dance material), then the normal "continuous" rating may be to high.  For those types of signal-a good rule of thumb is to limit the signal (with a slow attack type limiter-or know as a thermal limiter-say a couple of seconds) to 1/2 to 1/4 the continuous rating.

I know that sounds low-but subject your loudspeakers to that level and see what happens.

With an attack that long-the peaks will come through just fine-and unless you have that sort of material in your music-you will never see the thermal limter kick in.

[Jonathan Betts]

Great post Ivan.

FWIW I set my ITech Peak limiters at 120v(attack .010sec, release 1 sec) and RMS at  800w(attack 4 sec, release 6 sec) for my 728's. I use these default attack and release times as they were recommended by Crown as "proven values". I always have plenty of output, and rarely ever go into limiting.

[Geoff Doane]

FWIW I set my ITech RMS limiters at 800w(attack .010sec, release 1 sec) and Peak at 120v(attack 4 sec, release 6 sec) for my 728's. I use these default attack and release times as they were recommended by Crown as "proven values". I always have plenty of output, and rarely ever go into limiting.

Are you sure you don't have the RMS and peak  backwards?  The values may be correct, but the time constants seem wrong.

GTD

[Tim McCulloch]

Great post Ivan.

FWIW I set my ITech RMS limiters at 800w(attack .010sec, release 1 sec) and Peak at 120v(attack 4 sec, release 6 sec) for my 728's. I use these default attack and release times as they were recommended by Crown as "proven values". I always have plenty of output, and rarely ever go into limiting.

{edit comment}  I see you corrected the original.

I think you have those backwards.

For our VerTec 4880 (basically the same as the 728, settings-wise), we use 120v. peak voltage limiter with whatever attack/release JBL specs.  They let the user select the RMS limiter parameters, I use different numbers than you use.  Since my employer paid me to develop those settings he considers them proprietary... but I'll say the attack/release times are longer.

[Jonathan Betts]

Sorry folks. I originally edited post #4 to include those attack and release times for each limiter. I did indeed have them backwards. I edited post #4 again with the correct information. Thanks for the catch.

[Jonathan Betts]

Tim, would you consider the attack and release times I posted for both the RMS and Peak limiters to be adequate for average rock type shows?

[Tim McCulloch]

Tim, would you consider the attack and release times I posted for both the RMS and Peak limiters to be adequate for average rock type shows?

For subs I think the attack is too fast.  1ms or even 2ms should be fine.  The peak energy in a kick drum hit is in the first 10ms.

With subs and kick drum oriented music, so long as the peaks don't cause over-excursion you will have a relatively low heat build up.  If you do rap/hippy hoppy or metal with extended LF from the distorted bass guitar, the RMS limiters will be much more important.

[Jonathan Betts]

Thanks for the advice Tim. Would you recommend that I adjust my Peak limiter attack on my tops(SRX 715) to this value also.

[Yosi Melamed]

Thanks for the advice Tim. Would you recommend that I adjust my Peak limiter attack on my tops(SRX 715) to this value also.

Thank you all for posting, I think I got the hang of it.

Tim, Jonathan posted attack time of 0.010 sec (=10ms) so did you mean it was too slow or too fast when you suggested the 1-2ms peak limiter attack time?

[Tim McCulloch]

Thanks for the advice Tim. Would you recommend that I adjust my Peak limiter attack on my tops(SRX 715) to this value also.

Are you bi-amping the tops?  If so, you'd want that very fast attack (0.01-ish ms) on the HF driver, but you could probably get by with 2-5ms on the cone driver.  We don't have any 715 so I've not really looked into what would keep them happy in passive mode.  You might contact JBL by phone (not email) for further guidance.

[Tim McCulloch]

Thank you all for posting, I think I got the hang of it.

Tim, Jonathan posted attack time of 0.010 sec (=10ms) so did you mean it was too slow or too fast when you suggested the 1-2ms peak limiter attack time?

Overlooked the decimal place... oops.

The ITechs have a very short attack time available, IIRC it's around 0.01ms.  Sorry for the confusion.

[Jonathan Betts]

I run the 715's passive and they told me to use the default settings I listed in post 4. I figured I would ask around to see if others agree with this information.

The shortest attack time(peak limiter) i'm seeing in SA is 1.0ms. The longest is 0.100s.

[Justin Philip]

Sorry I didn't want to start a new thread on this.

I am going to get an I-Tech HD 5000HD bridged 4ohms (4000w) to use on a srx728s.

I have a Drive Rack 260. Primary use is kick drum and bass guitar.

What would I set my limiter to on the Itech? I am thinking of using the drive rack just for the tops and run the subs as auxfed into the itech.

Thanks!

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