ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 [2]  All   Go Down

Author Topic: Figuring my sub wattage based on FOH levels  (Read 2759 times)

Gordon Brinton

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 565
  • ID Verified
    • Raw Depth Sound and Raw Depth Video, Carlisle, PA
Re: Figuring my sub wattage based on FOH levels
« Reply #10 on: January 09, 2024, 10:00:02 PM »

I wouldn't want a limiter to be the deciding factor of how loud my show is.

No, I wouldn't either. It's not "loud" that I am seeking. I really just want to find a reliable way to know how much headroom I have left when I do start to get loud. I don't want to just keep pushing the system until I see red lights and then say, "I found it!". There must be easy to understand direct relationship between room level and watts delivered to the speakers without relying on lights. I want to feel more comfortable with knowing my sub's limits and behavior, and I want to feel confident that I have my limiters set correctly.
Logged
Member since 2005.

Brian Jojade

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3563
    • HappyMac Digital Electronics
Re: Figuring my sub wattage based on FOH levels
« Reply #11 on: January 10, 2024, 12:37:14 AM »

Having limiters set 'correctly' is going to be different for what you expect the limiters to do.

Personally, I like to run rigs where I know I can run them into a PAIN threshold far faster than I can cause damage to any components.  If I EVER see a red clip light during show operation that means I didn't bring enough rig. Period.

As long as your amps and speakers are appropriately sized, limiters really aren't needed.  If you're trying to squeeze every last ounce of output from your rig you can use a limiter to keep you kinda safer, but not really.

If you're using a limiter to protect against things like someone dropping a hot mic on the floor, well, that's a good use scenario.

As far as 'room level' and watts, well, every room and placement of the speakers is going to be different.  Heck, in a room you can move a few feet and the levels can be drastically different.  And power fluctuations needed to get a little more output can be dramatically greater than you expect.

Case in point, I use Crown iTech 5000 amps which are 2500 watts per channel.  They have a power meter on them.  For MOST shows, the reading on the amp is well under 100 watts.  It's kind of amazing how loud even 20 watts can be!! Granted that's an average draw and peak draws can be much higher.  The point is, the average watts is what makes the average sound level you hear.  The short bursts for kick give you the dynamic range you want.  Put a limiter on and you can crank the volume up a LOT more. The difference is you start to lose the dynamic range needed for that extra when you need it.

Therefore, limiters really should never be hit on the mains on a properly designed rig.
Logged
Brian Jojade

Chris Grimshaw

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1837
  • Sheffield, UK
    • Grimshaw Audio
Re: Figuring my sub wattage based on FOH levels
« Reply #12 on: January 11, 2024, 05:22:07 PM »

No, I wouldn't either. It's not "loud" that I am seeking. I really just want to find a reliable way to know how much headroom I have left when I do start to get loud. I don't want to just keep pushing the system until I see red lights and then say, "I found it!". There must be easy to understand direct relationship between room level and watts delivered to the speakers without relying on lights. I want to feel more comfortable with knowing my sub's limits and behavior, and I want to feel confident that I have my limiters set correctly.


The proper way to achieve this is to use amplifiers which have monitoring-over-network. I use the Powersoft T-series amps for this. With a little setting up, I can have a laptop at FOH displaying headroom for all the speakers in my system.


The problem you have is this: you can measure SPL, but you have no idea how hard each speaker is working. Is the 50Hz bottom end or the 100Hz punch louder? Where's your crossover point? Which cabinet is contributing more to the total SPL?


The best approximation I can find for you is this: subs on Aux. I don't particularly like the workflow, but it'll give you a level meter at FOH which will give you a reasonable idea of how hard the subs are working. NB - you'll need to think about where the crossover is applied to give sensible readings.



Chris
Logged
Sheffield-based sound engineering.
www.grimshawaudio.com

Paul G. OBrien

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1417
Re: Figuring my sub wattage based on FOH levels
« Reply #13 on: January 11, 2024, 09:43:49 PM »

I really just want to find a reliable way to know how much headroom I have left when I do start to get loud. I don't want to just keep pushing the system until I see red lights and then say, "I found it!".
Well.. that is the simple way to figure it out, push the rig until you see the clip indicators flash on the sub amp, note the mains level on the mixer when that happens.. both peak and continuous, and you can now work backwords to figure out the power levels the rig normally runs at. This assumes the system is configured the same each time.

There must be easy to understand direct relationship between room level and watts delivered to the speakers without relying on lights.
The lights are more accurate but some math will get you there too. The GXD8 has an input sensitivity of 3.9v rms, that means it needs an input signal of +14dbu (-10dB FS) to reach full output of 1200w rms into 4ohms and every 3dB down from that is 1/2 the power, so +11db is 600w, +8dB = 300w, etc. The one unknown here is your gain staging through the Ashly DSP, is it 1:1 input to output or do you have both inputs sumed to a mono output and/or the sub output boosted? If it is 1:1 then the main meters on your mixer will track as described above, but if you have the signal boosted in the DSP then it will be that amount lower on the mixer.
Logged

Paul G. OBrien

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1417
Re: Figuring my sub wattage based on FOH levels
« Reply #14 on: January 11, 2024, 10:03:24 PM »

If I EVER see a red clip light during show operation that means I didn't bring enough rig. Period.

As long as your amps and speakers are appropriately sized, limiters really aren't needed.  If you're trying to squeeze every last ounce of output from your rig you can use a limiter to keep you kinda safer, but not really.

LOL... you guys would hate doing the shows I do, the system is almost always undersized because of limited budgets and even when it's not the performers(DJs) will still attempt to wring every last watt out of it. Good limiting keeps me in business.
Logged

Steve-White

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1635
  • Fort Worth
Re: Figuring my sub wattage based on FOH levels
« Reply #15 on: January 11, 2024, 10:29:43 PM »

LOL... you guys would hate doing the shows I do, the system is almost always undersized because of limited budgets and even when it's not the performers(DJs) will still attempt to wring every last watt out of it. Good limiting keeps me in business.

Sometime we need to compare notes.  Same here and I do lots of DJ shows.  Everything many times runs Full Tilt and I like to bring it home in still functional for the next job.

From back in the day, when we built up ground stacks with discrete components, splayed 90x40 2" fiberglass horns, and analog compressor/limiters it's been about squeezing every db out of the system that it could produce and hold together.

I got it down to life of drivers.  4-0way systems with 12" low mids, had things dialed up to the point that adding another db would shorten the lifespan of the 12's - they wouldn't burn out - well they would if ya really leaned on them, but pull them back from burning voice coils to the point were they literally mechanically fell apart.  Then, back 'em down another db and things held together.  Using Ashly SC-50/55's.

Carrying that forward to today, if using outboard processing nothing has changed if you want to push things, assuming the drivers are powered-up well amp wise.  You can still burn things down or tear things up without clipping amps.  Finding the sweet spot still takes trial end error - you can get close with test gear, but deploy it and see how it performs and if it holds together doing so is the final test.

This is what the OP is seeking to do, only with gear that has presets.  Then there's Gain Staging and overall system calibration so the meters on the console mean something beyond the signal condition of the console itself.
« Last Edit: January 14, 2024, 11:15:26 AM by Steve-White »
Logged

Chris Grimshaw

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1837
  • Sheffield, UK
    • Grimshaw Audio
Re: Figuring my sub wattage based on FOH levels
« Reply #16 on: January 12, 2024, 12:06:11 PM »

Well.. that is the simple way to figure it out, push the rig until you see the clip indicators flash on the sub amp, note the mains level on the mixer when that happens.. both peak and continuous, and you can now work backwords to figure out the power levels the rig normally runs at. This assumes the system is configured the same each time.
 The lights are more accurate but some math will get you there too. The GXD8 has an input sensitivity of 3.9v rms, that means it needs an input signal of +14dbu (-10dB FS) to reach full output of 1200w rms into 4ohms and every 3dB down from that is 1/2 the power, so +11db is 600w, +8dB = 300w, etc. The one unknown here is your gain staging through the Ashly DSP, is it 1:1 input to output or do you have both inputs sumed to a mono output and/or the sub output boosted? If it is 1:1 then the main meters on your mixer will track as described above, but if you have the signal boosted in the DSP then it will be that amount lower on the mixer.


I'm afraid this won't work.
A vocal-heavy mix won't push the subs, but a bass-heavy mix will. They'll hit similar levels on the VU meters.


Chris
Logged
Sheffield-based sound engineering.
www.grimshawaudio.com

Art Welter

  • Hero Member
  • *****
  • Online Online
  • Posts: 2239
  • Santa Fe, New Mexico
Re: Figuring my sub wattage based on FOH levels
« Reply #17 on: January 13, 2024, 08:07:30 PM »

Jeff from JTR gives details on both RMS and Peak limiter settings, but he doesn't say which one to use.

Thus, my quest is, (and what I should have asked to begin with,) which limiter to use and and where to set it? How do I discover how hard I am already pushing my subs?

Both RMS and separate peak limiter settings are required to protect for different program material.
Long term (RMS) power burns coils, short term (peak) can tear up cones/diaphragms.

Logged

Gordon Brinton

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 565
  • ID Verified
    • Raw Depth Sound and Raw Depth Video, Carlisle, PA
Re: Figuring my sub wattage based on FOH levels
« Reply #18 on: January 14, 2024, 08:29:11 AM »

Both RMS and separate peak limiter settings are required to protect for different program material.
Long term (RMS) power burns coils, short term (peak) can tear up cones/diaphragms.

Both!! I hadn't thought of that. Thanks for waking my ass up!
I've never used two limiters on one speaker before, but perhaps I will now.
The GXD8 has an RMS limiter in the DSP. I can set that to 800W slow.
The Ashly Protea speaker management has a peak limiter that I can set for fast attack and release near the max of the amp channels.

Hmm! I'll work out the details. Thanks again.

EDIT: Corrected spelling.
« Last Edit: January 14, 2024, 08:36:56 AM by Gordon Brinton »
Logged
Member since 2005.

Ivan Beaver

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 9570
  • Atlanta GA
Re: Figuring my sub wattage based on FOH levels
« Reply #19 on: January 16, 2024, 08:31:44 AM »

No, I wouldn't either. It's not "loud" that I am seeking. I really just want to find a reliable way to know how much headroom I have left when I do start to get loud. I don't want to just keep pushing the system until I see red lights and then say, "I found it!". There must be easy to understand direct relationship between room level and watts delivered to the speakers without relying on lights. I want to feel more comfortable with knowing my sub's limits and behavior, and I want to feel confident that I have my limiters set correctly.
You could always put a little cable that has a connector )whatever type you want) to hook up a voltmeter to the output of the amp.

That way you can get an idea of the "average" (slow response) of the voltage delivered.  Then you use the "nominal impedance" to figure out the wattage.  wattage=voltage squared divided by impedance.

Yes the actual impedance will be different, and the meter response will be slow, but it will give you a decent idea of the power you are delivering.

Another idea is to simply put a "old school" wattmeter (ie refrigerator watt meter) in series with your speakers.  That way the impedance will be part of the meter deflection
 
Logged
A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

ProSoundWeb Community

Re: Figuring my sub wattage based on FOH levels
« Reply #19 on: January 16, 2024, 08:31:44 AM »


Pages: 1 [2]  All   Go Up
 



Site Hosted By Ashdown Technologies, Inc.

Page created in 0.025 seconds with 19 queries.