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iTech limiter settings help

iTech limiter

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#1 Mark Paschal

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Posted 22 October 2012 - 04:55 PM

Hello everyone!  This forum is extremely helpful but I'm having trouble finding some specifics for my set up.  

I have an 2x iTech 6000 and an XTi 1000 driving 2x Peavey QW218 and 2x QW4F with the tops being in biamp mode.  I have the iTechs in stereo on subs and mids and the XTi in stereo on the tops.  I'm happy with the settings with respect to crossover points and delays, etc., but have I don;t know how to set the limiters.  I blew both subs and a horn, so I want to set the limiters to help keep that from happening again.  I understand that this isn't a catch-all for clipped signals but I'd like to get as much protection as possible.  

The Peavey subs are rated at 1600/3200/6400 watts and the tops are 1200/2400/4800.  

Can anyone help me with the best settings for the peak voltage and RMS limiter settings?

Thanks!  

-Mark

#2 313DJ

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Posted 22 October 2012 - 09:15 PM

my jbl srx728s subs are rated at 1600/3200/6400 same as yours,the rms setting for your subs will be 1600 and the peak setting will be 160,also your tops wattage  are the same as my ev qrx 218s subs and the settings for those is 1200 for the rms and 138 for the peak hope this helps the numbers came from crown tech support

#3 dakos

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Posted 23 October 2012 - 03:19 AM

Dear Mark,
Sorry to hear you fryed so many drivers... I think you should read this document:
http://www.bennettpr...undamentals.pdf
It will give you a better understanding of the insides of speaker damage.

Getting back to your question, every type of music requires a specified amount of headroom, from the most compressed and relaxed cafe music that requires 6dB of headroom all the way to a live rock/metal show that needs 20-24dB of headroom, every 3dB increment equals twice the wattage, every 10dB increase of the volume equals 10 times the power, so as you can see the minimal amount of headroom needed is about 4 times the power, and the maximal amount of headroom needs 20 times the power. So to answer your question properly I would need to know what type of music you play through your rig.

Also you need to take into consideration speaker power compression, that will happen if you continuously feed your speakers power in the ball park of their rated continuous power. Yes, I know, you buy speakers with a certain power rating and now I'm sayin you can't use it... Power compression is usually the reason we set our RMS limiter to about 1/2 - 1/4 of the continuous power rating of the speaker.

Note that even when setting the limiters correctly, you only protect the speakers against thermal overload. To also try and protect it against mechanical overload you need to also set the High Pass Filter in the amp to filter out those unreproducible frequencies, to the correct setting in accordance with your specific speakers frequency response (-3dB point of the speaker). This little thing might be the reason why you fried those LF drivers drivers.

The formula to calculate the limiter settings is:
RMS Limiting wattage= 1/4-1/2 of the Continuous speaker rating
Peak Limiting voltage = SQ Root (Peak speaker rating * speaker impedance)

For the QW218 a good staring point would be:
Also for the RMS limiter set the attack to 4sec and the release to 6 sec.
Also for the peak limiter set the attack to 0.010sec and the release to 1 sec.

Not sure what the attack and release figures for the QW4F at the moment so I started a thread for you on the Peavey forum:
http://forums.peavey.com/viewtopic.php

Unlike current generation of XTIs, the limiter on the older XTIs is pretty limited in its usage and settings, all it has is three settings, -3dB. -6dB and -12dB, the only setting I see usable for you is the -3dB but its action is not that pleasing sonically (google: shattered glass) so we're kind of limited in our limiting options here :(

I can't emphasise it enough, NEVER CLIP the amps!!!

By now you're begining to understand the theory behind limiting and speaker damage, there are many more uses for limiters and compressors but we'll not get into those here.

Avi

#4 Mark Paschal

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Posted 23 October 2012 - 02:42 PM

Wow, than you so much for your replies and help at the Peavey forum!  I feel like I'm a lot closer to understanding how to set the DSP.  

I play rock and country through the rig, loud club and outdoor situations.

#5 dakos

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Posted 25 October 2012 - 08:31 AM

I have translated the values Marty posted on our thread to the values
you need to input the i-Tech limiters:

The specs for the QW218 can be downloaded from the Peavey website.
For the Subs on the QW218,
RMS limiter should be:
Attack of 100 mS, Release of 1000 mS,
RMS Threshold should be 1225W and the Peak Limiter threshold at 157V

The specs for the QW4F can be downloaded from:
http://assets.peavey...ls/qw4specs.pdf

For the Mids on the QW4F:
RMS limiter should be:
Attack of 40-50 mS, Release of 400-500 mS
RMS Threshold should be 870W and the Peak Limiter threshold at 117V

For the compression driver on the QW4F:
RMS limiter should be:
Attack of 10-20 mS, Release of 100-200 mS
RMS threshold should be 60W and the Peak threshold at 44V

You should recalculate the data yourself to varify my calculations corectness.





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