Danley Sound Labs Limiter Guide + ??

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5meohd
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Danley Sound Labs Limiter Guide + ??

#1 Post by 5meohd »

I'm working on setting limiters. I don't know why I struggle with this, but I do.

This was given to me by Danley:

Danley Sound Labs
How to set limiters
The best way to set accurate limiters is to measure the actual output voltage of the amplifier. Some of the limiters in the “built in DSP” amplifiers are not very accurate-so the numbers in the program can be a bit misleading.
Below are the steps.
1: DISCONNECT THE SPEAKERS!!!!!!!!!!!!!!! Or at least one terminal. You can easily damage loudspeakers if they are not disconnected during this procedure.
2: Hook the voltmeter to the output terminals of the amplifier.
3: Use a Sine wave generator to produce the measurement signal. This can be from any source-physical generator-digital console-smart phone etc. The freq needs to be somewhere in the passband of the speaker that is hooked up. The exact freq is not important. For subs 60Hz works well-for full range cabinets 1KHz works well and for HF devices 5K works well.
HOWEVER you have to be sure to know what your meter is capable of. If it is a better quality wide bandwidth meter-then you are good. If it is a less expensive meter-then it is best to use 60Hz, since that is where the meter is most accurate. If the DSP amp is providing high pass functions-then it is best to turn these off. This will not affect the limiting-since the limiting “should” be the last thing in the signal chain.
4: There are 3 different basic limiter settings/types. Depending on the particular limiter used-there may be 1, 2 or all three available to you. The 3 types are Peak-RMS/ continuous and Thermal/long term/heating.
5: The Peak limiter should be set to attack as fast as possible. With a release about 15 times the attack time.
6: The RMS or Continuous attack should be set to around thehighpass freq that the passband will pass. So for 100Hz, which is 11.3ms (1130/freq), the attack time would be around 11ms. Release times should be around 15 times the attack time. For 1000Hz it would be 1.1ms.

An easy way to remember it is 1000Hz is approx. 1ms (1.13 at sea level). Half of that (500Hz would be twice as long =2ms) Twice the freq 2000Hz is half as long (0.5ms).

The difference between 1.13 and 1ms is not enough to worry about.
7: The Thermal or long term limiter or heating limiter needs a much longer attack time. 100 times the time constant of the lowest freq in the passband is a good starting number. It could always be shorter if desired. The release time should be at least twice the attack time and up to 10 times the attack time-this is user “defined” as to the musicality of the limiter and how hard the system is pushed. If the user is likely to push the system into thermal limiting a good bit-a longer release time is suggested.
8: You need to set the PEAK voltage first-since it is the highest value. Turn the limiter OFF and inject the signal into the amplifier WITH THE SPEAKERS DISCONNECTED!!!!! Turn the level up until you exceed the needed voltage. We are talking VOLTAGE here-NOT power-so it does not matter what the impedance of either the loudspeaker or how many are hooked to the amplifier.
Let’s say the PEAK voltage that is needed is 100 volts. Turn the level up to around 110-120V-the actual voltage is not important-just a bit higher than the value needed. Now turn the limiter ON and start decreasing the threshold until the meter comes down to 100V. You are done.
NOTE” Pay attention to the peak or limit light on the amplifier in question. If this lights up before you reach the desired peak voltage, then set the limiter to just below (maybe 0.5dB) this light turning on. You will not get any more “headroom” out of the amplifier by setting the voltage higher-and the meter will no longer be reading a sine wave-so the value it shows will be incorrect.
It is always a good idea to have any internal limiting/clip eliminator etc turned on.
9: Next set the RMS or CONTINUOUS voltage. You can leave the gain of the signal where it is and start decreasing the threshold until you get to the value needed. This is usually ½ of the PEAK voltage (6dB)-or in this case 50V.
10: Now to set the THERMAL or HEATING or LONGTERM limiter. This one needs to be set a bit slower-since the attack time can be much longer than the others-so after making adjustments-give it time to “settle in”. Adjust the attack time to the desired level. This varies from between ½ of the RMS (6dB) to around 70% (3dB). So in this case somewhere in the range of 25-35 volts. The exact value highly depends on the typical content of the source. For highly compressed or long duration sources (dance club music) then it is a good idea to go towards the lower side. For more “normal” music-go towards the higher side.
11: Turn the signal source off and disconnect it.
12; Hook up the speakers as normal.
13: Play music and have fun!


All is well. Except that the spec given to me by the same guy for the SH69 model we own doesn't mention a "Peak" limiter value at all. Instead it says:

Limiters:
RMS Limiter: 62 Volts
Thermal Limiter: 31 Volts, 2.0 Seconds Attack, 1.5X Release (multiplier of Attack)
XMax Limiter: 62 Volts at 40 Hz


It seemed like a nice enough guide to then try and apply some of their logic to our T60. Bill's guide just says:

The Lab 15 power and displacement ratings are both 600 watts, so 60 volts is the maximum allowable.

I think Ivan's guide just put too much info in front of us, yet didn't do a full job of totally explaining the entire fundamentals including interchangeable terminology, so now we are a little stuck in confusion limbo.

Having some production chops under my belt making a lot of techno, I understand how the various limiter settings will have a different effect, so can someone explain to us which one would match Bill's 60 volt recommendation?

We have the potential for 3 "limiters" in our signal chain since we use a Behringer X Air, Ashly Protea and QSC PLX2 amps.

In order: We can set a compressor with max ratio on the input channels in the Behringer, then set a limiter in the Ashly which is the final DSP block in it's chain, then turn the limiters on in the QSC amps.

In last nights testing we found that the QSC clip lights don't engage until well above 120V. So it's clearly fine to just leave those limiters engaged, but they aren't exactly protecting our speakers. (2502 bridge mono for Sh69 and 3602 parallel mono for T60).

What we've done so far is set the Ashly Limiters to the voltage of 62v for Danleys and 60v for T60 with the attack/release settings closest resembling Ivan's "RMS Limiter".

And prior to that in the signal chain, we set the compressor on the Behringer to act closest to his "Peak Limiter" setting, except we aren't sure we have the correct voltage. We set it to about 124v based on the description he used saying that "rms" is typically about half of the "peak".

I greatly appreciate your time and consideration reading this post. THANKS!

- Ben
4 T60's
2 Danley Sound Labs SH69

Ashley Protea
QSC PLX2
Crown CDi

Bruce Weldy
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Re: Danley Sound Labs Limiter Guide + ??

#2 Post by Bruce Weldy »

You should be able to hear any distortion and turn it down. If you really want a limiter in the chain on the Danleys, I'd consider something between the thermal and xmax limit that they suggest. I'd guess 40-45 volts would be safe and keep things under control. Don't get lost in the weeds with the different type of limiters. Use the Ashley-it's the only device with a brick wall limiter. The QSC doesn't have a limiter and using any kind of limiting in the mixer is not a good idea....all you'd have to do it change the scene, then all of the limiting just went out the window.

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

5meohd
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Re: Danley Sound Labs Limiter Guide + ??

#3 Post by 5meohd »

Bruce Weldy wrote: Mon May 08, 2023 11:23 am You should be able to hear any distortion and turn it down. If you really want a limiter in the chain on the Danleys, I'd consider something between the thermal and xmax limit that they suggest. I'd guess 40-45 volts would be safe and keep things under control. Don't get lost in the weeds with the different type of limiters. Use the Ashley-it's the only device with a brick wall limiter. The QSC doesn't have a limiter and using any kind of limiting in the mixer is not a good idea....all you'd have to do it change the scene, then all of the limiting just went out the window.
QSC doesn't have limiters? Why does it's manual state that it does? What does the switch called "Clip Limiters" do?
4 T60's
2 Danley Sound Labs SH69

Ashley Protea
QSC PLX2
Crown CDi

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Bill Fitzmaurice
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Re: Danley Sound Labs Limiter Guide + ??

#4 Post by Bill Fitzmaurice »

As the name says they prevent the amp from clipping. They don't limit the output voltage.

5meohd
Posts: 126
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Re: Danley Sound Labs Limiter Guide + ??

#5 Post by 5meohd »

Interesting.


Is 60v the maximum voltage the T60 should see regardless of the limiter type?

Do you have recommendations on timing components of the limiter settings for the T60?

Do you believe in this theory of using several limiters in series? I found a Powersoft PDF speaking to this effect as well.

thanks
4 T60's
2 Danley Sound Labs SH69

Ashley Protea
QSC PLX2
Crown CDi

Bruce Weldy
Posts: 8288
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Danley Sound Labs Limiter Guide + ??

#6 Post by Bruce Weldy »

5meohd wrote: Mon May 08, 2023 12:49 pm Interesting.


Is 60v the maximum voltage the T60 should see regardless of the limiter type?

Do you have recommendations on timing components of the limiter settings for the T60?

Do you believe in this theory of using several limiters in series? I found a Powersoft PDF speaking to this effect as well.

thanks
On the subs, you need only one limiter type - brick wall. Period. Timing components are for allowing the signal be gently limited after a certain point. But, that would let the limiter exceed the limit....that's something for mixdown in the studio where blowing speakers isn't an issue. You aren't looking for a musically pleasing limiter - you want to clamp down the signal at all costs when it hits the wall - this is about saving speakers, not quality of audio.

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

5meohd
Posts: 126
Joined: Thu Nov 18, 2010 4:47 pm

Re: Danley Sound Labs Limiter Guide + ??

#7 Post by 5meohd »

This sure is a welcoming environment to learn, engage, and grow...
4 T60's
2 Danley Sound Labs SH69

Ashley Protea
QSC PLX2
Crown CDi

5meohd
Posts: 126
Joined: Thu Nov 18, 2010 4:47 pm

Re: Danley Sound Labs Limiter Guide + ??

#8 Post by 5meohd »

https://www.powersoft.com/wp-content/up ... n_v1.0.pdf

"As you can see the peak limiter is working correctly, as it
maintains the level below the 70 V, but the RMS power increase
up above the maximum allowed level, this because is dependent
by the crest factor of the musical program. For this reason is very
important use two limiters, one for over-excursion protection
and one for thermal protection (RMS power)."
4 T60's
2 Danley Sound Labs SH69

Ashley Protea
QSC PLX2
Crown CDi

Bruce Weldy
Posts: 8288
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Danley Sound Labs Limiter Guide + ??

#9 Post by Bruce Weldy »

5meohd wrote: Mon May 08, 2023 3:48 pm https://www.powersoft.com/wp-content/up ... n_v1.0.pdf

"As you can see the peak limiter is working correctly, as it
maintains the level below the 70 V, but the RMS power increase
up above the maximum allowed level, this because is dependent
by the crest factor of the musical program. For this reason is very
important use two limiters, one for over-excursion protection
and one for thermal protection (RMS power)."
Excursion limits are typically lower than thermal (at least in every speaker I've ever seen). Since the excursion is lower, it's the one you have to use with folded horns as you can't hear the driver farting out like you would in a front-loaded speaker.....that would be the signal to turn it down before you blow it. With horns, you won't hear the distortion - thus you won't turn it down.....until it just quits.

That's why limiting is absolutely necessary in horns - the determining factor is always excursion. Could you get a driver to fail thermally? Sure. But, it would take continuous high levels in hot weather to get you there. In the decade plus that I've been on this forum, I can't remember a single time someone had a thermal failure. It's always too much juice that blows 'em up, not heat.

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Bill Fitzmaurice
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Re: Danley Sound Labs Limiter Guide + ??

#10 Post by Bill Fitzmaurice »

The Power Soft document is a major simplification. The voltage limits in the plans prevent mechanical damage, which is by far the #1 concern with horn loaded subs, as you can't hear them distorting. We don't mention limiting tops because you can hear them distort long before they will be damaged. Long term thermal damage is caused by excessive compression, which can result when you limit to a given voltage and then constantly drive at that voltage, with no dynamic range. Not only does it cook voice coils, it also sounds like crap. So you don't need another piece of kit to prevent it. You just have to be sensible.

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