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Amp for running 6x Oberton XB1500
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Jo bg View Drop Down
Young Croc
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That's for long term heating control and will Kick in after seconds i think.
Your "1500 watt" speaker is rated to survive 2 HOURS, in OPEN  AIR and with a 6 db crest factor signal (somebody correct this if wrong!).
Now with some modern music is not uncommon to see 3db or even less crest factor in bass, so this brings your speaker to 750 watt before meltdown, but still for two hours and in cool open air. Enclose it in a box that keeps the heat inside and run it for 12 hours straight and 750 watt will still cook it. So 1/4 for horns and 1/3 for reflex boxes, that are obviously vented seems safe (and pros like Toasty or Danley engineers say this, not me).
Ideally your limiting should allow levels to rise with higher crest factor material, so better dsp allow you to have 
- a quick peak kimiter , could be around program or even more, depends on the enclosure, the goal is to keep excursion in check and protect speakers from very fast transients that could cause mechanical damage
-an rms limiter that lets fast transients (like a kick drum) tru to preserve dynamics, timing (as always) is frequency dependent. This keeps the average level in a safe thermal zone but allows more through than the last
-thermal limiter , very attack long times, maybe 5 6 seconds under 100Hz, kicks in only when the threshold is reached for a long time, so only with high duty cycle/low crest factor  program.
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Actual power is a tricky one,  but as Kyle said about 1/4 if the rating is around about where most drivers are close to the edge.

Drivers are rated in voltage,  as per AES test these days,  those obertons are tested at 89V RMS long term, so setting a limiter a little below that should keep them safe, bear in mind they are tested in free air so in a small closed chamber they will build up heat more easily.

What amp you use is up to you, the higher the voltage the louder they will get but a carefully set RMS limiter should keep them safe thermally.

Unfortunately most budget processors do not have an RMS limiter, just a peak limiter,  i am working on a solution for that ;)
James Secker          facebook.com/soundgearuk
James@soundgear.co.uk               www.soundgear.co.uk
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Originally posted by Jo bg Jo bg wrote:

That's for long term heating control and will Kick in after seconds i think.
Your "1500 watt" speaker is rated to survive 2 HOURS, in OPEN  AIR and with a 6 db crest factor signal (somebody correct this if wrong!).
Now with some modern music is not uncommon to see 3db or even less crest factor in bass, so this brings your speaker to 750 watt before meltdown, but still for two hours and in cool open air. Enclose it in a box that keeps the heat inside and run it for 12 hours straight and 750 watt will still cook it. So 1/4 for horns and 1/3 for reflex boxes, that are obviously vented seems safe (and pros like Toasty or Danley engineers say this, not me).
Ideally your limiting should allow levels to rise with higher crest factor material, so better dsp allow you to have 
- a quick peak kimiter , could be around program or even more, depends on the enclosure, the goal is to keep excursion in check and protect speakers from very fast transients that could cause mechanical damage
-an rms limiter that lets fast transients (like a kick drum) tru to preserve dynamics, timing (as always) is frequency dependent. This keeps the average level in a safe thermal zone but allows more through than the last
-thermal limiter , very attack long times, maybe 5 6 seconds under 100Hz, kicks in only when the threshold is reached for a long time, so only with high duty cycle/low crest factor  program.

Yes 6dB crest factor pink noise is used but you will not find much music program with long term crest factors much lower than that, 3dB is a continual sine wave mastered at 0dB and despite what people say im yet to find a tune with that in, there is always some dynamic.  

The 1500W rating is v^2/re ,   on the old AES test it was V^2/ nominal impedance but they changed to so they could give bigger numbers, and now more high power bass drivers are designed with a lower RE to exploit this and yeild a bigger power number...  but 89Vrms ^2 / RE is "1500w" program is defined as 2x that and peak is 4x, as the 6dB crest factor signal will have peaks at 178V / "6000W"
James Secker          facebook.com/soundgearuk
James@soundgear.co.uk               www.soundgear.co.uk
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It depends a lot on what amp / dsp you have, not many have the luxury of three way limiting like described, so often you have to compromise.
But you should look for at least a peak and an rms limiter to still protect the system without loosing too much performance.

Some amplifiers have good voltage or clip limiters, that if correctly sized can substitute peak limiters. 

You can check excursion in hornresp for your horn driver combination to find the power level where it's excursion limited and use it to find your peak limiter settings . Considering power conpression and the fact that xmax is not yet the point of mechanical failure you could squeeze something more than calculated here, but remember that between 1000 and 1500 watts there is less that 2 dB of difference, so decide if it's worth.

For rms limiting ... Go with the pros, if you want it safe 1/4 of power as it's f or a horn with closed chamber, and rise it up to 1/2 power if you are feeling brave , keeping things in control and have a high crest factor signal, but at 1/2 power you can allready cook  drivers with the right track, or a long session. If the amp lights stay on all the time and don't flicker up and down is a good signal of low crest factor (or slow leds), and a warning to lower the limiter back to 1/4. 

Don t get too worried about leaving 3 theoretical dB on the table, there is not so much difference , it will probably sound better and last till the end of the night making you and the crowd happier than a short party and smoked drivers. 
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Worth noting that there is a big difference between and RMS power limiter like you get on the powersofts, and and RMS voltage limiter, for RMS power around 1/4 power is about the limit for most drivers, for an RMS voltage limiter the drivers are rated at 89Vrms in free air so in a reflex / vented cabinet 70Vrms should be fairly safe.
James Secker          facebook.com/soundgearuk
James@soundgear.co.uk               www.soundgear.co.uk
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Originally posted by Timebomb Timebomb wrote:

A lot of the time when people say "i feed x drivers with 1000W" thats not really whats happening,  it might be an amp capable of giveing 90V rms at 8 ohms / "1000W"  at clip but with signal crest factor and resistance rise they might only be getting 100W of actual power.  


Hallelujah Clap

And that's why some great systems still run off 900w PPX's etc...Just well looked after systems kept out of danger zone. A few DB down at peaks that's all
It's everything, not everythink!
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Originally posted by Timebomb Timebomb wrote:

Worth noting that there is a big difference between and RMS power limiter like you get on the powersofts, and and RMS voltage limiter, for RMS power around 1/4 power is about the limit for most drivers, for an RMS voltage limiter the drivers are rated at 89Vrms in free air so in a reflex / vented cabinet 70Vrms should be fairly safe.


 Maybe i got you wrong, but doesn't this relate more to the time constants involved than in power limiter vs voltage limiter?
I can call it 1100 watts power or 89 volts into 7.2 ohm , am I missing something? (I think you know more than me, not being a prick)
the power limiters are set lower because supposed to kick in later and protect from heat buildup, while the rms limiter, set higher, will keep the driver close to where it's happy but still not protecting fully from intense and continuous abuse.

If you don't have powersoft or linea you have to choose between extreme safety , so setting your rms limiter to 1/4 to act as a power limiter, or give it a higher limit to do rms limiting , but you are now allowing some risk.


Edited by Jo bg - 11 October 2018 at 5:49pm
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Originally posted by Jo bg Jo bg wrote:

That's for long term heating control and will Kick in after seconds i think.
Your "1500 watt" speaker is rated to survive 2 HOURS, in OPEN  AIR and with a 6 db crest factor signal (somebody correct this if wrong!).
Now with some modern music is not uncommon to see 3db or even less crest factor in bass, so this brings your speaker to 750 watt before meltdown, but still for two hours and in cool open air. Enclose it in a box that keeps the heat inside and run it for 12 hours straight and 750 watt will still cook it. So 1/4 for horns and 1/3 for reflex boxes, that are obviously vented seems safe (and pros like Toasty or Danley engineers say this, not me).
Ideally your limiting should allow levels to rise with higher crest factor material, so better dsp allow you to have 
- a quick peak kimiter , could be around program or even more, depends on the enclosure, the goal is to keep excursion in check and protect speakers from very fast transients that could cause mechanical damage
-an rms limiter that lets fast transients (like a kick drum) tru to preserve dynamics, timing (as always) is frequency dependent. This keeps the average level in a safe thermal zone but allows more through than the last
-thermal limiter , very attack long times, maybe 5 6 seconds under 100Hz, kicks in only when the threshold is reached for a long time, so only with high duty cycle/low crest factor  program.

It seems like all of those limiters are vitally important, yet, to my knowledge, only very high end DSPs have them. Is there any way i can set such limiting with a dbmark DP24?
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Reading through this just reminds me how complicated and confusing this buisness is lol. Just as I thought I had a really solid grasp on how much power to feed drivers and limiting etc you guys come up with all that hahaha. May take me a couple reads through but all the input is appreciated.
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Originally posted by Jo bg Jo bg wrote:

Originally posted by Timebomb Timebomb wrote:

Worth noting that there is a big difference between and RMS power limiter like you get on the powersofts, and and RMS voltage limiter, for RMS power around 1/4 power is about the limit for most drivers, for an RMS voltage limiter the drivers are rated at 89Vrms in free air so in a reflex / vented cabinet 70Vrms should be fairly safe.


 Maybe i got you wrong, but doesn't this relate more to the time constants involved than in power limiter vs voltage limiter?
I can call it 1100 watts power or 89 volts into 7.2 ohm , am I missing something? (I think you know more than me, not being a prick)
the power limiters are set lower because supposed to kick in later and protect from heat buildup, while the rms limiter, set higher, will keep the driver close to where it's happy but still not protecting fully from intense and continuous abuse.

If you don't have powersoft or linea you have to choose between extreme safety , so setting your rms limiter to 1/4 to act as a power limiter, or give it a higher limit to do rms limiting , but you are now allowing some risk.

Kind of, an RMS voltage limiter will protect from long term abuse, that is what they are for, and set right they are in effect are a power limiter.

The difference with those "true power" limiters is they are actually measuring current delivered, so can calculate the actual power delivered to the speakers and be set as a power rating rather than a voltage rating.  imo they are not really required as it can be very hard to say how much "true power" a speaker can take, and drivers are rated in RMS voltage anyway. 

An RMS voltage limiter set at 70V will act similarly to the true power limiter set at 1/4 power as those points are both around about the same, when the coil warms up 70V long term RMS limit into say 12 ohms is only about 400W of real power, and resistance will get higher than that as the coil gets hotter, when the coil is cooler then it will let more power / current flow, as resistance is lower, drivers in effect compress the actual power level drawn but if you get them to hot they will blow, there is a point of diminishing returns though. 
James Secker          facebook.com/soundgearuk
James@soundgear.co.uk               www.soundgear.co.uk
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Originally posted by junoprobelaunch junoprobelaunch wrote:

Reading through this just reminds me how complicated and confusing this buisness is lol. Just as I thought I had a really solid grasp on how much power to feed drivers and limiting etc you guys come up with all that hahaha. May take me a couple reads through but all the input is appreciated.

There is a lot of things people say and ways manufacturers specify things that can make it confusing,  if you try to forget power and think of it in volts it gets simpler,  unfortunately with a DP24 the best you can do is set the peak limiter and estimate a minimum signal crest factor and hope the signal does not get to dense for to long to heat up the drivers too much.
James Secker          facebook.com/soundgearuk
James@soundgear.co.uk               www.soundgear.co.uk
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Originally posted by Timebomb Timebomb wrote:

Originally posted by junoprobelaunch junoprobelaunch wrote:

Reading through this just reminds me how complicated and confusing this buisness is lol. Just as I thought I had a really solid grasp on how much power to feed drivers and limiting etc you guys come up with all that hahaha. May take me a couple reads through but all the input is appreciated.

There is a lot of things people say and ways manufacturers specify things that can make it confusing,  if you try to forget power and think of it in volts it gets simpler,  unfortunately with a DP24 the best you can do is set the peak limiter and estimate a minimum signal crest factor and hope the signal does not get to dense for to long to heat up the drivers too much.

How do you convert a power rating in watts into volts?
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