Setting limiters

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PrismAudio
Posts: 28
Joined: Fri Mar 25, 2016 11:12 am

Setting limiters

#1 Post by PrismAudio » Wed Apr 20, 2016 12:57 am

So I've just completed my first dual 12 Tuba 60 and
I need some help properly setting the limiter threshold
On dbx Venue360

My question is what is the procedure.

My logic is this

Play 30hz sine, with gains on the amps at full, and the limiter threshold all they way down I would then proceeded to bring up the limiter threshold while monitoring voltage untill the max voltage for the dual lab 12 is achieved?
My Current Rig

Speakers:
4 - Omni 12
8 - J-Array Omni 12
6 - 2x12 Tuba 60s

Processing & Power
Console - Allen & Heath SQ6
Processing - DBX Venu360
SUBS - 3 x QSC PL236
LF Omnis - 2 x QSC PL325
HF Omnis - 1 x QSC PL325

CoronaOperator
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Location: Medicine Hat, Alberta, Canada

Re: Setting limiters

#2 Post by CoronaOperator » Wed Apr 20, 2016 2:33 am

You have the right idea. A couple pointers: First, make sure you do this without your subs hooked up, just a voltmeter. This will save your ears and if you make a mistake no drivers are lost. Second, 30hz is too close to the recommended highpass filter of the T60's and will already be attenuated a bit by the filter giving you a false reading of max voltage. Remember, the filters are a slope and not a cliff, they start before the value listed on the screen. Bump that up a bit to about 60 hz, that is in the middle of the T60's passband. 3rd, I'm not sure if you are in Australia and up and down is reversed but in my head bringing the limiter down would be lowering the voltage level and up would be giving it more voltage :D .

Once your limiters are set you are protected no matter what. After that you need to set your output gains to match. I usually play the same 60 hz signal on the mixer with the vu meter set to where you want your limiters to kick in. Some people like the system to max out at 0 dB, others the first or second red, you decide. Then set your output gains on the 360 up and down so that the limiter just kicks in where you have your mixer output level set. Then you are protected and your still have the fader travel that you want, you can always turn the amp gains down if the bass is too heavy in the room you are playing in.
Built:
17" width 10" driver Autotuba
2 x 29" width dual Lab12 Tuba60
6 x DR250 2510/asd1001
In progress:
2 x DR250 2510/asd1001
For best results, point the loud end of the array towards the audience

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escapemcp
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Re: Setting limiters

#3 Post by escapemcp » Wed Apr 20, 2016 2:52 am

It would be worth testing the setting before you connect anything up - i.e. feed a really hot signal into the system and make sure that the limiter does indeed clamp the voltage to the recommended maximum.

PrismAudio
Posts: 28
Joined: Fri Mar 25, 2016 11:12 am

Re: Setting limiters

#4 Post by PrismAudio » Wed Apr 20, 2016 9:24 am

Awesome thanks for the help guys, nope not Australia. From Canada.

I gusss what a mean buy down is on the limiter chart on my dbx buy moving the cursor down, you reduce the dB.
My Current Rig

Speakers:
4 - Omni 12
8 - J-Array Omni 12
6 - 2x12 Tuba 60s

Processing & Power
Console - Allen & Heath SQ6
Processing - DBX Venu360
SUBS - 3 x QSC PL236
LF Omnis - 2 x QSC PL325
HF Omnis - 1 x QSC PL325

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Tom Smit
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Location: Sarnia, Ont. Canada

Re: Setting limiters

#5 Post by Tom Smit » Wed Apr 20, 2016 11:14 pm

Are your drivers wired in parallel or in series?
TomS

PrismAudio
Posts: 28
Joined: Fri Mar 25, 2016 11:12 am

Re: Setting limiters

#6 Post by PrismAudio » Wed Apr 20, 2016 11:54 pm

Parallel so 800w RMS into 4ohms, I've read that voltage is equal
to the square root of watts times resistance which gives me 56 volts

I put my multimeter on the posts on the amplifier, but only got
To 30 volts on before it got super loud and was getting back to 0 On the limiter. I'm using a QSC PL236 good for 1100 into 4

I'm also not using the greatest of multimeters either, just a cheapo mastercraft.
My Current Rig

Speakers:
4 - Omni 12
8 - J-Array Omni 12
6 - 2x12 Tuba 60s

Processing & Power
Console - Allen & Heath SQ6
Processing - DBX Venu360
SUBS - 3 x QSC PL236
LF Omnis - 2 x QSC PL325
HF Omnis - 1 x QSC PL325

CoronaOperator
Posts: 1648
Joined: Wed Mar 25, 2009 7:07 pm
Location: Medicine Hat, Alberta, Canada

Re: Setting limiters

#7 Post by CoronaOperator » Thu Apr 21, 2016 12:21 am

PrismAudio wrote:Parallel so 800w RMS into 4ohms, I've read that voltage is equal
to the square root of watts times resistance which gives me 56 volts
The plans state that 50 V is the maximum voltage allowed. 4 ohms is nominal, not actual. Nominal means "for all intents and purposes but not really". There is more to it than that equation of yours. First of all, impedance varies with frequency, take a look at a dual T60 impedance graph here. Select the "+" button to expand the image. The impedance varies from ~2.8 ohms to ~14 ohms depending on frequency. Second, x-max is usually the limiting factor of subwoofer drivers, not power handling. Bill has done the math for us, follow it to the letter. I would limit it just under that 50v, 49v is where I have my settings. As a test I once ran one of my dual T60s very briefly at 52V (the next click up from 49V on the limiter) and it sounded stressed so don't exceed the 50V limit.
PrismAudio wrote:I put my multimeter on the posts on the amplifier, but only got
To 30 volts on before it got super loud and was getting back to 0 On the limiter. I'm using a QSC PL236 good for 1100 into 4
That's the whole point of these things :D . I have 2 of these guys, wait until you get an EDM song that has a 28 Hz drop, no matter where you are in the room or what you are doing, you WILL stop and go H*ly F**k!
Built:
17" width 10" driver Autotuba
2 x 29" width dual Lab12 Tuba60
6 x DR250 2510/asd1001
In progress:
2 x DR250 2510/asd1001
For best results, point the loud end of the array towards the audience

PrismAudio
Posts: 28
Joined: Fri Mar 25, 2016 11:12 am

Re: Setting limiters

#8 Post by PrismAudio » Fri May 13, 2016 12:57 pm

Yeah i figured out what i was doing wrong. My DJM was getting fixed due to an unfortunate accident where a DJ spilled a whole bottle of beer in it. I try to enforce a no drink rule on stage but sometime you cant catch them all. anyway i was pretty much using an XLR to 3.5mm AUX cord and running that from a computer to generate Tones. I just got the DJM back, i just ran tones through the CDJ and DJM. Much much much much better

Yeah, i had the first one going at full, just playing some rowdy progressive psy-trance. I had my neighbors at the end of the street come and ask if i could turn it down because "Its Loud as fuck inside my house"

GREAT SUCCESS!!!
My Current Rig

Speakers:
4 - Omni 12
8 - J-Array Omni 12
6 - 2x12 Tuba 60s

Processing & Power
Console - Allen & Heath SQ6
Processing - DBX Venu360
SUBS - 3 x QSC PL236
LF Omnis - 2 x QSC PL325
HF Omnis - 1 x QSC PL325

ACUA
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Joined: Sun Sep 25, 2016 6:21 pm

Re: Setting limiters

#9 Post by ACUA » Wed Oct 12, 2016 12:12 am

:noob: can i bump this thread and rephrase the question so that I might understand the principle better? I own crown xls series amplifiers. i understand that with these amps and potentially others, the gain structure is fixed and the gain ratio is different depending upon the size. I read that with these crowns in order to reach peak output i need an input of 1.4v to the amplifier. i hope to obtain some blanket knowledge to help me fully understand setting limiters

here is where i need clarificaiton:
I am under the understanding that the "sensitivity" dial on the amps is to modulate or limit the input to the amp, and with my crowns that needs to be 1.4v or less depending on needs. so any input signal over 1.4v will clip my amplifier because we have exceeded the fixed gain structure the amp is capable of?

some amplifiers dont stick to the input needing to be at 1.4v for max output, like peavey, i believe they have a fixed gain ratio and need different input levels to achieve a maximum out put for each different size amplifier. example is peavey cs-4000 which is rated at 800w into 8ohms with a fixed gain ratio of 40 meaning that to achieve the 800w or 80v the input must be at 2v??? if i had this amp and needed to limit to 50v i would need to limit the input to the amp to 1.25v. with PA amplifiers being so diverse unity gain cant be a fixed voltage and maybe that is why the need for the sensitivity dial on the amplifiers you have to dial them in depending on what input they are getting, being that it could be widely varied? since the amp has a fixed gain structure a limiter is valuable and this noob sees exactly why.

help me apply...
the amp i plan to run once i build a second cab is a crown xls2500 rated at 440w at 8ohms, so
sqr(440x8)=59.3v for an amp gain ratio of 42.378 meaning that i would need to limit the amp to 50v for a tuba45 with lab12, so
at 1.179v input to the amp i would limit the amp output to 50v at a nominal 8ohm load. would this work for crown xls1500 bridged? so sqr(1050x8)=95.65v gain ratio 65.465 and would need to set the input to 0.763v input to amp.

I guess my question is: Will the limiter on a dbx driverack limit whatever comes in to it regardless what voltage it is? if it was 1.5v or 5v i can limit whatever it is to a specific level, say 1.179v or 0.763v depending on what amp i am running? to me i could dmm the output cable of my driverack to the sub amplifier and be able to verify correct limiting ya!!!!

does any of this make sense enough to anyone that you can give me your feedback about any of it? you guys are great i appreciate it.
Last edited by ACUA on Wed Oct 12, 2016 9:42 am, edited 1 time in total.
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Grant Bunter
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Re: Setting limiters

#10 Post by Grant Bunter » Wed Oct 12, 2016 4:28 am

^ While amp input sensitivity can be adjusted on some amps, I'm wondering if you're over thinking it all.

One shouldn't bridge amps where possible, because it dramatically increases the value of transient output as well.

Perhaps it would be better if you described your entire signal chain as a starting point.
eg Mixer to Driverack to amp.


Also, and this will be hard for you, stop thinking in watts.
You can't measure watts, watts are a calculation derived by multiplying current and voltage, so near impossible to measure on the fly.
Just work with voltage, it can be measured instantly.

Also, don't think of input voltages/multipliers/amp gain, work with relative constants, like unity on your mixer.
Why? Because resistance is frequency dependant...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
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ACUA
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Re: Setting limiters

#11 Post by ACUA » Wed Oct 12, 2016 9:35 am

i dont think i am over thinking it, i need to pull out my DDM and test inputs and outputs and that will help me truly understand what is happening. i am simply running a mixer to a driverack to amplifiers.

dont tell me to stop thinking in watts, amps are rated in watts or at least my crown amps are. watts is power where voltage is only potential, and if you did read my above post the only place i talk about watts is when i listed the specs provided by the manufacture such as 440watts at 8ohms. i had no other spec to go off of and had to use the wattage spec to convert to voltage in order to ask my questions or to state what i think i know and see if im getting close or am way off!!!

i may error by talking nominal resistance as i understand the impedance varies with frequency but i cant comprehend the principles any other way than nominal.

you say you cant measure watts on the fly, but if you put an amp clamp on your cable and a volt meter and do the math you can measure it on the fly. do a little math and you can calculate the equivalent horse power of your system! i am talking about playing a 60hz sine wave while measuring as that will give most consistent measure through DMM. I understand the dynamics of music enough to know that a sine wave is in no way close to the way music graphs and so a sine wave rms power will effect equipment very differently than rms music power will. i dont fully understand why driver manufactures and amp manufactures don't post voltage specs, i guess 440watts sounds better than 59v and its a sales ploy. to me amplifiers should post voltage output ratings as that is what they do, amplifiers are generally quite simple they ramp the voltage of the input signal a certain amount right. the actual wattage is varied by load impedance which varies with frequency as you stated, to me amps with a wattage rating is not quite accurate in principle, even car amplifiers put out voltage not wattage, nothing puts out wattage, wattage is the result of the voltage of the amp and the load!!! but you all know that
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CoronaOperator
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Re: Setting limiters

#12 Post by CoronaOperator » Wed Oct 12, 2016 10:00 am

ACUA wrote: amplifiers are generally quite simple they ramp the voltage of the input signal a certain amount right. the actual wattage is varied by load impedance which varies with frequency as you stated,
That is exactly what they do, they do that until they hit their voltage limit (rail voltage) or run out of current capacity (power supply, output IC's, etc). They should really be called voltage amplifiers, not power amplifiers.
ACUA wrote: nothing puts out wattage, wattage is the result of the voltage of the amp and the load!!
Exactly, now you got it.
Built:
17" width 10" driver Autotuba
2 x 29" width dual Lab12 Tuba60
6 x DR250 2510/asd1001
In progress:
2 x DR250 2510/asd1001
For best results, point the loud end of the array towards the audience

Bruce Weldy
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Location: New Braunfels, TX

Re: Setting limiters

#13 Post by Bruce Weldy » Wed Oct 12, 2016 10:47 am

Please keep in mind that my (and others) comments are based on the context of the subject of this thread - Setting Limiters
ACUA wrote:i dont think i am over thinking it, i need to pull out my DDM and test inputs and outputs and that will help me truly understand what is happening. i am simply running a mixer to a driverack to amplifiers.
Actually, you are over-thinking it in today's world. If you are running a mixer set at +4 for a balanced output and you run the driverack at +4 balanced output - that's all you need to do. The XLS series does not have the ability to select your input sensitivity like the old Crowns did years ago. It's pretty much plug and play nowadays.

dont tell me to stop thinking in watts, amps are rated in watts or at least my crown amps are. watts is power where voltage is only potential, and if you did read my above post the only place i talk about watts is when i listed the specs provided by the manufacture such as 440watts at 8ohms. i had no other spec to go off of and had to use the wattage spec to convert to voltage in order to ask my questions or to state what i think i know and see if im getting close or am way off!!!
In order to set limiters correctly, you must stop thinking in watts. You are right that you have to deal with watts in order to pick an amp of the correct output - but that's only because they quit putting the voltage output on the specs like they used to. Wattage numbers are bigger and sexier (marketing hype) - but since this thread is about setting limiters - wattage has no bearing on the process.
i dont fully understand why driver manufactures and amp manufactures don't post voltage specs, i guess 440watts sounds better than 59v and its a sales ploy. to me amplifiers should post voltage output ratings as that is what they do, amplifiers are generally quite simple they ramp the voltage of the input signal a certain amount right.
Amen....



Because we see this issue over and over on the forum, we tend to jump right to the how-to because most folks coming here have been indoctrinated that watts are the most important thing in the world and also try to come up with a way to set the limiters on their driverack using math - and that's just not the correct way to do it.

Sure, you can probably get your system dead perfect on sensitivity settings by manipulating the input controls on the amp, but the trade-off is having some yahoo crank up your knobs, thus totally negating your limiters and blow up your drivers.

That's where the over-thinking it comes in - if you get tied up on the input side of the equation, you can leave the output side open to disaster. That's why anyone who is going to use their system in public should always turn the amps all the way up to ensure that the limiter will do it's job. Might you trade off a little perfection in input sensitivity? Yeah, but at the cost of drivers - it's a small price to pay. And you really won't notice the difference in the sound anyway.

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4 - OT12 2512 Melded/NSD2005
1 - T24
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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whines
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Re: Setting limiters

#14 Post by whines » Wed Oct 12, 2016 2:03 pm

If I recall correctly, Crown does list voltages for the Xti in its manual. Not for the XLS though.
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ACUA
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Re: Setting limiters

#15 Post by ACUA » Wed Oct 12, 2016 2:16 pm

you said turn the amps all the way up and leave them that way!!! "That's why anyone who is going to use their system in public should always turn the amps all the way up to ensure that the limiter will do it's job" I take that for good information mister. and i agree with you. is there any situation or manufacture of amplifier that you should not run wide open on the amp?
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