Max Voltage during Live Sound???

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T_Gowan
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Max Voltage during Live Sound???

#1 Post by T_Gowan »

Hi every one

I was checking my sub voltage limit, Mixer-DCX-Amp into my meter. I have presets for different amp combination so I was setting up for my Amp to T39 voltage. Got it set OK just under the 50V mark.
I was borrowing a meter with max voltage hold function so I thought I would see what the meter said with pre recorded music going through. I was surprised . The max voltage reading when the limiter started to kick in was only 24. ?? volts. I could get it to go up to over 30 with the limiter hitting constantly . Are the peaks that fast that the meter , a Circuit Test DMR 5200, can not follow.

Is this to be expected.

This exercise was to see what the internal limiter on my Mackie DL1608 could do so I went with limiter I trust all the time in my DCX to compare . But im not sure what Im seeing on my meter

Any thoughts??

Tom G
DR200 x2
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whines
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Re: Max Voltage during Live Sound???

#2 Post by whines »

I've heard that multimeters can't always track actual music signals very well, which is why one is advised to set the limiters with sine waves. Perhaps that's what you are seeing?
2xJ15, THT, 4xT39 3012 (2x15", 2x20"), 2xSLA Pro, 2x short SLA Pro (Dayton), W6

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BrentEvans
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Re: Max Voltage during Live Sound???

#3 Post by BrentEvans »

If your meter has a "max" or "hold" setting you may want to try that. Transients in music happen too fast for some meters to display even if they do register.
99% of the time, things that aren't already being done aren't being done because they don't work. The other 1% is split evenly between fools and geniuses.

T_Gowan
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Re: Max Voltage during Live Sound???

#4 Post by T_Gowan »

I was using the max hold function at the time which is why I was a little confused :noob:
DR200 x2
T24 16" x2
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DCX2496
DEQ2496 x2
FBQ2496
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djtrumptight
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Re: Max Voltage during Live Sound???

#5 Post by djtrumptight »

I'm a DJ and i know EXACTLY what you mean about playing recorded music after setting your limiter with sine waves,its just something that has to be dealt with when dealing with recorded music.I recently posted a video of my voltmeter connected to the sub channel to measure the actual output while the sub was playing.For a brief second i seen 44 volts but on average it was around 20 volts.
Built:
2 Autotuba's MCM 55 2421
8 T48's 24"wide 3015 LF
2 DR 250's melded Deltalite II 2510
2 DR 250's flat Deltalite II 2510
2 SLA HT systems
1 Table Tuba Dayton DCS 255-4
2 T 39's 20" wide 3012 LF
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2 SLA Pro's

CoronaOperator
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Re: Max Voltage during Live Sound???

#6 Post by CoronaOperator »

I just finished 2 dual tuba t60's and I measured pretty much identical voltage to you using a Driverack 260 as the limiter set using a 60hz sine wave and 50 volts limit. With prerecorded music the limiter lights start to flash around 24 volts measured with a normal DMM. My Galaxy SPL meter also registers around 132 dBc's at 1 meter (slow or fast doesn't matter) when the lights just start to flicker. If I go by the published SPL charts and add 6 dB's for 2 cabinets, and another 26 dB's for voltage gain (50v) I should be measuring around 138 dBc's. The 6 dB difference in SPL reflects the voltage being halved (24 volts measured vs 50 volt limit).

I'm also curious if we are getting the full potential out of the cabs or if the 6dB crest factor of pre-recorded music just doesn't register fast enough on the DMM and the SPL meter.
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yigba
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Re: Max Voltage during Live Sound???

#7 Post by yigba »

I'm also curious about this for two reasons:

1) I also have the DL1608 and would love to know how those limiters work

2) I have always felt that using the limiter procedures here - limiting the voltage via a 60 Hz sine wave with my DSP to 50 volts for T39's - really cuts the volume of the cabs to an unacceptable level. I mean who actually runs their board to the max - i.e. right before clipping? And if you limit at the max of the board (say +10 db on the main fader of the DL1608) but run the board at 0 db aren't you just cutting 10 db off the output of the subs? That makes no sense to me and the proof is in the perceived volume.

There is absolutely no chest thump with the T39's when they are limited and I am shocked by that. Cabs were made by Leland so I don't doubt that they were made correctly.

yigba
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Re: Max Voltage during Live Sound???

#8 Post by yigba »

Actually when you think about it the RMS power going into the T39's should be roughly 25 volts, right? I am getting that figure from the peak limited power of 50 volts - if you limit at 50 volts then the average should be 25 volts because 1/4 of the peak power is half the voltage, no?

So maybe those readings do make sense if they are only average readings?

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Re: Max Voltage during Live Sound???

#9 Post by Bruce Weldy »

yigba wrote:And if you limit at the max of the board (say +10 db on the main fader of the DL1608) but run the board at 0 db aren't you just cutting 10 db off the output of the subs? That makes no sense to me and the proof is in the perceived volume.

.
Well then, either run the fader up to +10 or set your limiter based on -0-. Doesn't matter - the limiter will still kick in at the same amount of voltage regardless of whether the gain comes from the board or the processor....it's the last thing in the chain.

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Bill Fitzmaurice
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Re: Max Voltage during Live Sound???

#10 Post by Bill Fitzmaurice »

djtrumptight wrote:I recently posted a video of my voltmeter connected to the sub channel to measure the actual output while the sub was playing.For a brief second i seen 44 volts but on average it was around 20 volts.
That's because when setting the limiter you have a tone that's at a constant level. Music is not a constant level source. 6dB of dynamic range translates to a 2:1 voltage ratio. A 6dB dynamic range is common with recorded sources, 10dB or more is common with live sources unless heavily compressed.

yigba
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Re: Max Voltage during Live Sound???

#11 Post by yigba »

So then say a live mix has 12 db of dynamic range - wouldn't this justify compressing the entire mix by roughly 6db to not squash the dynamics and yet also increase the volume (via makeup gain) without blowing up the divers? You would then limit based on the voltage.

Does that make sense?

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Bill Fitzmaurice
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Re: Max Voltage during Live Sound???

#12 Post by Bill Fitzmaurice »

yigba wrote:So then say a live mix has 12 db of dynamic range - wouldn't this justify compressing the entire mix by roughly 6db to not squash the dynamics and yet also increase the volume (via makeup gain) without blowing up the divers?
It does make sense. Live music has a very wide dynamic range, and usually needs compression so that the soft sections aren't too soft and the loud sections aren't too loud. Knowing how much compression to use comes with experience.

Grant Bunter
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Re: Max Voltage during Live Sound???

#13 Post by Grant Bunter »

yigba wrote: 2) I have always felt that using the limiter procedures here - limiting the voltage via a 60 Hz sine wave with my DSP to 50 volts for T39's - really cuts the volume of the cabs to an unacceptable level. I mean who actually runs their board to the max - i.e. right before clipping? And if you limit at the max of the board (say +10 db on the main fader of the DL1608) but run the board at 0 db aren't you just cutting 10 db off the output of the subs? That makes no sense to me and the proof is in the perceived volume.
The whole idea of setting up your mixer to just before or at clipping is to reproduce what you might get signal wise when in use. You might not get there any given day or night, but it's where you could get to. And that should be your "hottest" signal ever.
If it isn't, or you change your "hottest" signal point eg 0dB rather than +10dB on the masters, then you need to redo your limiter settings.
Of course, the end result is to protect your drivers.
yigba wrote:There is absolutely no chest thump with the T39's when they are limited and I am shocked by that. Cabs were made by Leland so I don't doubt that they were made correctly.
Really?
I'm not sure why you don't get chest thump.
You have to remember that chest thump will not occur until the relevant frequencies reach 110dB. If your listening position is somewhat back from the cab(s), then you have to allow loss of 6dB per doubling of distance, eg, if you're 8 yards away, you should be reading an SPL of 128dB, but the only place that you will actually get thump is at 1 yard.

I have T39's too. They are "only" BP102 loaded, so their limit is 35V.
I have had chest thump a plenty, without hitting the limiter on my DCX, especially in recorded music (most of the live music I do I don't go quite as loud, but I've gone close to getting thump often enough).
If I can do that with 35V limited cabs, I'm wondering if you haven't set you chain up properly.

As far a compressing the output at your desk, you've got to work with the band at the time.
I've played in bands that have played songs that, within the song itself, has a greater than 6dB dynamic range from quiet to loud passages (and back again). If you compress to 6dB, you take that away from the song...
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Bruce Weldy
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Re: Max Voltage during Live Sound???

#14 Post by Bruce Weldy »

Uhhhhh.....not to state the obvious......but, just in case....are your amps turned all the way up?

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


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yigba
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Re: Max Voltage during Live Sound???

#15 Post by yigba »

Yup, sub amp all the way up.

And it never occurred to me about the whole average vs peak being a difference of 6 db's which is also half the voltage and 1/4 of the watts. All depends on how one looks at things.

Being that we're concerned with displacement killing the sub drivers moreso than any type of thermal meltdown I understand the limiting rationale but that is effectively cutting our average output in half. In order to get that output higher you should figure out the best way to compress the mix, but not too much so that you kill the dynamics. Then simply limit the peak voltage thereafter, which theoretically should allow the average to be higher because the peaks of the mix will be slightly compressed and lower.

Phew, I think my head is gonna explode.

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