RMS limiting/Peak limiting/ long term

[Pro Sound Guy]

I wanted to start a little conversation about loudspeaker protection and the "safe runnning all week long" settings.

Is it correct in RMS limiting/limiter to limit the signal 1/4 to 1/2 of rated RMS for a loudspeaker for long term use?

Example my subs are rated at 1000W rms per loudspeaker in a dual loudspeaker box (4ohm). I calculated 89.9 or 90volts rounded off.

So I should run them at 45volts Rms limited? I read this on a Crown site and I want to get some input.

I also saw they recommend two limiters. One for RMS limiting and one for peak limiting.

I do not see an RMS limiter in my digital mix or in the digital xover. I see dynamic limiting which is peak I believe.

Sooo....for loudspeaker protection an RMS limiter is the way to go eh?

 

 

 

[dboomer]

First I should say that there is not one and only one way to do this. Do you mix wearing a helmet? You would be safer wearing a helmet. How much risk is reasonable vs cost?

 

Ok, jokes aside. Where you set things depends on how much risk you can tolerate, how much control you have over the system (to prevent others from screwing it up) and how much skill you have running the system.

 

Lets take your example ... a speaker rated for 90 volts. If it is rated using EIA or AES methods then it is rated to hold that power continuously for 2 to 8 hours. You will never get that to happen using music as a source. Even highly compressed music with only 3 dB of dynamic range is going to bounce back and forth between full and half power and that does't count all the little stops between notes. With that small of a dynamic range that music would sound like crap. Now if you limit to 1/2 or 1/4 power you will have more protection but you will have thrown away 3/4's of the system you paid for.

 

So to my way of thinking what you want to do is to limit the system to a volt or two less than 90v but have a system that is way bigger than what you need and simply not run it at capacity.

 

On the subject of RMS limiting and peak limiting ... having both is better. But the likelihood of damage would be overwhelmingly from long term and not peak power in a normally running system. Usually you should be able to hear potential problems before you actually damage drivers. If your system starts sounding like crap it probably doesn't matter what the numbers say. You are in the danger zone and you need to make changes. Peak power can be a factor in setting up new systems or is egregious mistakes.

 

So my basic suggestion would be to use an amp that can cleanly deliver the full peak power rating of the driver and then limit the RMS voltage to just slightly below the published rating (assuming you understand and believe those specs). Then run the system reasonably, at well below it's capabilities and if you hear it start to bark then pull in the reigns.

 

If you've installed a full roll cage in your auto then you might wanna run at 1/4 power on the limiter

[Pro Sound Guy]

I have a capable system. It is all EAW and plenty of power. I have never really had an issue running it without a safety net but I am educating myself on this by reading on the net and now reading great posts like yours.

I have gone to digital in a loudspeaker processor and now a digital mix. I see the dynamic limiting in the settings on both.

I wanted to learn about peak limiting verse RMS limiting and what people are doing. Thanks Don.

[agedhorse]

I have a similar yet different approach to protection, but I am also more conservative so my approach may not be ideal for you.

 

 

 

if possible, in an ideal world would Like to use 3 different limiting algorithms long term RMS, short term RMS and peak. Long term rms is used to detect not enough rig for the gig over a period of maybe a few minutes, threshold about .75xRMS rating of speaker, short term (about 3-5 sec) RMS set to about the RMS rating of the speaker and a peak limiter set to the peak rating of the speaker (but it is critical to know how the amp defines peak power and what units are used in the limiter threshold (peak or RMS). Mixing up units can be a big issue when you need it most and you may need to convert units so all are consistent.

[Pro Sound Guy]

Conservative is a good thing when it comes to possible reconing. Heating of the voice coil. Power compression.

Over excursion. Inside show not to much of a worry. Outside shows long term is where things can

get pushed pretty hard.

[agedhorse]

Power compression is not just a thermal effect, there is also a major electro-magnetic and electro-mechanical component to this.

 

 

 

The harder you beat a speaker, the shorter it's lifespan, especially once you exceed it's linear limits.

[Unalaska]

I'm reading this after pulling a 15" EWI out because it seized up. 10yr driver, lots and lots of use with various amps and rooms. Some VC discoloration, there's a definite break in the winding at the bottom of the driver. Usually powered at 700w high passed at 100hz.

 

 

 

Head up: this thread may open a can of worms, but it'll be a good read.

[agedhorse]

I'm reading this after pulling a 15" EWI out because it seized up. 10yr driver, lots and lots of use with various amps and rooms. Some VC discoloration, there's a definite break in the winding at the bottom of the driver. Usually powered at 700w high passed at 100hz.

 

 

 

Head up: this thread may open a can of worms, but it'll be a good read.

 

I wonder how far out of spec it was the last 5 years and how much the performance suffered (even if you didn't realize it)?