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RMS limiting with a crossover

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danparrott View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote danparrott Quote  Post ReplyReply Direct Link To This Post Topic: RMS limiting with a crossover
    Posted: 29 April 2020 at 11:56pm
Hi guys,

Recently learned the difference between RMS and peak limiting and how one protects against thermal damage whilst the other against over excursion. I have a full rack of MC2 E Series (non dsp) and was wondering what my options are for RMS limiting. I’m currently using a db mark DP28 crossover which I believe only allows peak limiting. Basically I think I have 3 options, not sure if the first is even available so please let me know.

1 - buy a stand-alone 8 in 8 out RMS limiter to put between crossover and amps.
2 - replace the db mark to something that has both rms and peak limiting.
3 - replace amps and crossover with powersoft k series with dsp and use their truepower and peak limiters.

I’m not made of money so would rather not shell out on a whole new rack but want to be able to have my speakers running close to full potential without having to babysit the rig looking out for redlining DJs. What is out there that can help me with this?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timebomb Quote  Post ReplyReply Direct Link To This Post Posted: 30 April 2020 at 8:58am
New LMS is the solution if you dont want to shell out for new amps with DSP.  The truepower limiters are not RMS voltage limiters, they are different as they actually measure current on the output.  The powersofts have separate RMS voltage limiters.
James Secker          facebook.com/soundgearuk
James@soundgear.co.uk               www.soundgear.co.uk
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danparrott View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote danparrott Quote  Post ReplyReply Direct Link To This Post Posted: 30 April 2020 at 9:29am
Okay thanks, can you recommend any good LMS capable of this? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jo bg Quote  Post ReplyReply Direct Link To This Post Posted: 30 April 2020 at 10:22am
Linea Research Asc48 has very interesting limiting options in my view.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote danparrott Quote  Post ReplyReply Direct Link To This Post Posted: 30 April 2020 at 10:50am
I looked into this, anyone have any idea about how the crossover is simulating the driver temp? Seeing as it has no idea how many drivers are connected, what kind of cab they’re in etc? I’d be using it for flh so would get hotter quicker than reflex 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote re-production Quote  Post ReplyReply Direct Link To This Post Posted: 30 April 2020 at 11:01am
it doesn't detect the temperature of the driver but you tell it the longer term power handling of the driver (RMS) which should protect the driver from overheating if set correctly. The peak limiter protects agains short bursts of too much power which would result in too much excursion rather than burn out the voice coil.
The value for the long term power handling varies from driver to driver and for the same drivers varies from box to box depending on how well it dissipates the heat from the driver. 
Drop here!
From my knowledge the RMS limiter should be set to kick in before there is too much thermal compression but this is a hard thing to measure so isn't exact.
Here's a paper explaining the different types of damage to a driver and which limiter helps stop it.

It's specific to linea research (which have great limiters on them if set correctly) but the concepts apply to other Xovers.

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danparrott View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote danparrott Quote  Post ReplyReply Direct Link To This Post Posted: 30 April 2020 at 12:17pm
Okay thanks I’ll have a read
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Post Options Post Options   Thanks (0) Thanks(0)   Quote callumtruds Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2020 at 12:38pm
It's not quite what your looking for but another option could be to use an automatic volume control unit instead of getting a rms limiter/new crossover.
They can be picked up 2nd hand at decent prices 
(about 150 pounds for a avc2) 
The formula sound avc2 or drawmer sp2120 are great units. I use the avc2 in conjunction with peak limiters on my crossover and never had any blown drivers.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote danparrott Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2020 at 12:19am
Callum I might be wrong but doesn't an AVC work off peaks? therefore allowing RMS to essentially reach your peak value (square wave) and fry the drivers? I have been recommended a drawmer so I will have another read about how it works
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Post Options Post Options   Thanks (0) Thanks(0)   Quote re-production Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2020 at 10:25am
An AVC is for managing a system that won't have an engineer controlling the volume of the overall system, the vast majority of these do not sound musical and if it is something you need to rely on will destroy the dynamic range of the system. Although the RC1 leveliza is meant to do control the volume without destroying the dynamic range.
Drop here!
You need individual limiters on each component of the system to protect the drivers, like the peak and RMS limiters on crossovers.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote danparrott Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2020 at 10:26am
Yep thats what I thought cheers
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Post Options Post Options   Thanks (0) Thanks(0)   Quote callumtruds Quote  Post ReplyReply Direct Link To This Post Posted: 04 May 2020 at 1:02am
Paragraph from the formula sound user manual 
"If the average operating level is kept below the internally set threshold the AVC2 has no effect, if the average programme level exceeds the threshold the AVC2 will hold the output level at the threshold setting."  

My reading of the manual makes me believe it works off the RMS level (manual is worth a read)

From real world use it lets peaks through exactly the same as if i take it out of my signal chain. 
You can hear each protective increment drop the level slightly, but even when output level has been reduced it still lets the peaks through the same (as far as i can tell)

i have heard the drawmer sounds better when transitioning between protection levels but otherwise a very similar unit. 

Hope that clears it up abit Smile
Callum 
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