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How many limiters?


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#1 ericels

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Posted 04 July 2005 - 09:37 PM

I just did an outside show with my full system and I thought I would get more SPL than I did.  I was at about 98 db at 20 meters.  Here is a description of what I am doing:  

When I hit 0 to + 6 db on the console, the amps are at 0.  I haved not changed any of the sensetivity settings or cut db in other places, except eqs of course.  

I am currently using 3 I-Techs: a 4K for highs, a 6K for Mids and an 8K for subs.  I set up my system using anywhere from 1 main box and one sub per side to three main boxes and three subs per side (the full system).  The main boxes each have a 200 watt horn and a 800 watt driver, program watts at 8 ohms.  The subs each are rated at 1200 watts at 4 ohms, program.  I've set up three different presets using the IQ software so the amp's limiters would match the 1, 2, or 3 box per side configuration.  I figured the nominal impedance and the peak voltage using the appropriate formulas so to properly (I believe) set the average power limiter and peak voltage limiter.  Here is an example:

3 main boxes and subs per side:  4k- average power limiter 300 watts @ 3 ohms, 79.89 peak voltage, 6K- average power limiter 1200 watts @ 3 ohms,  159.78, peak voltage, 8K- average power limiter 1800 watts @ 2 ohms, 154.49 peak voltage.

So does this all sound like I am on the right track?  Matching the amps with the boxes, setting the limiters?

Second:

Does setting the average power limiter to the average power of my speakers, adjusting the watts and the load for the number of boxes for each preset, overly limit the SPL the system is capable of producing?  Do you feel I had my system safely producing its max SPL?  Can I just use the peak voltage limiter to guard against damage and turn off the average power limiter to increase the SPL?

Sorry for the long post, but your insight in all of these areas would be greatly appreciated.  I put together a worksheet with each of my system configurations that I could email if you wanted to see how I have set up my other presets.

Thanks so much,

Eric

#2 ericels

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Posted 12 July 2005 - 10:21 PM

Can anyone respond to this post?

#3 DGlass

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Posted 14 July 2005 - 01:19 PM

Your best bet for verification of any of this is the speaker manufacture themself.

The Average Power example you gave for using 3 mains and subs per side I believe is more correct for 1 main and sub per side but not three. So you would be limiting the power going to all three speakers to what one speaker should be limited to. Your settings should be closer to 600w/3ohms for the highs, 2400 watts/3ohms for the mids and 3600watts/1ohm for the subs. For what you have set up the system is throttled back in the Average Power Limiter for what the system can do. sad.gif

Impedance of a speaker is not a fixed number but varies with frequency so the sub amp is probably loaded two low, when all three subs are connected per side of the amplifier. Using the 4 ohm nominal impedance for each speakers you would get a 1.3 ohm load with all three speakers. 1.3 ohms is closer to 1 ohm than 2 ohms. Yes the I-Techs will drive a 1 ohm load better than any other amplifier but you are leaving yourself no headroom for peaks in the program material.

The IT-6000 for the Mids probably doesn’t need Average Power limiting as the IT6000 does 2500 watts into a 2 ohm load.

Now for the Peak Voltage Limiter….. The Peak Voltage number should come from the speaker manufacture as this is something they test for and is not easily calculated.

Answer to question:
Does it sound like I am on the right track? Matching the amps with the boxes, setting the limiters?
*No, see above.

Does setting the average power limiter to the average power of my speakers, adjusting the watts and the load for the number of boxes for each preset, overly limit the SPL the system is capable of producing?
*With your original calculations…. yes you are throttling back the system. You will need different presets for each configuration of boxes.

Do you feel I had my system safely producing its max SPL?
*No. With your original calculations you are throttling back the system.

Can I just use the peak voltage limiter to guard against damage and turn off the average power limiter to increase the SPL?
*You can use either or both if they are setup correctly.

#4 ericels

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Posted 14 July 2005 - 10:32 PM

O.K.  Thanks for the information.  I will make the proper adjustments and go from there.