Setting limiters

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Bill Fitzmaurice
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Re: Setting limiters

#16 Post by Bill Fitzmaurice »

ACUA wrote:dont tell me to stop thinking in watts,
If you think in watts how do you set your limiter? A DMM can't measure watts. As is the case with most newbies here you need to wipe the slate clean of much of what you learned elsewhere, because much of it is wrong. That's because so much of it is related to marketing. We're not into marketing, we're into engineering. Engineers never think in watts.
is there any situation... that you should not run wide open on the amp?
When you have to back off well below 0dB on your mixer for the level desired. If you do that the signal to noise ratio worsens. Instead back off on the amp attenuators. That won't affect the limiting, if they can't exceed maximum voltage at full they won't exceed it at less than full.

Grant Bunter
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Re: Setting limiters

#17 Post by Grant Bunter »

ACUA wrote: 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!
Seems I may have upset you.
Please don't be upset, I (and we) are simply trying to help.

Sure, you can do what you stated above and work out watts, but that is no where near as quick as a simple glance at DMM output in volts.

Please remember that the limit called for, for a given driver, in the plans, is a voltage displacement limit, and that often does not equate with what one might expect in comparison to driver specs in watts (because it goes back to the driver and what it does in the design)...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 6 with melded array wired series/parallel.
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ACUA
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Re: Setting limiters

#18 Post by ACUA »

when i said "dont tell me to stop thinking in watts" what i also said is that the only reason i even mentioned watts was because the only spec i had concerning my particular amplifier is in watts. i did a math conversion in my post (to let you see where i am coming from with all of this, to see if i am getting it right) which got me to the voltage spec. from that point on i never talked watts until i was told not to think about it. it upset me a little because i was not stuck on watts, my entire first post on this thread was in voltage besides stating the amp specs which are in watts. Im sorry my equipment is mainstream and in watts.

i am a generator technician by trade, generators are rated in watts, its the common term of measurement used and understood for power generation, knowing the wattage is how you know how much work is being done. i am not an engineer, but i can aspire to become educated. I have came here to the Bill Fitzmaurice world because i believe there is something here. my understanding in general conversation, taking watts is a common term for power, its like talking in decibels, how loud is it, how much power does your system have, how much power does it take to reach a certain spl level. i was under the understanding that many sound guys used wattage to calculate how much equipment was needed for venues, i have heard it said 3watts per person, or so many watts per square foot of space etc, are these things not talked about like this? i read some of you have pretty big rigs, some have been in the trade for longer than i have been alive. when you plan a gig, do you not look the place over and evaluate,saying this place needs x amount of power, x amount of drivers etc, to me if 50v limited at 8ohm nominal gets you 300watts, each cab is 300watt rated, you could easily say i need 110db in this venue and an expert could say based on the size of the space i need 12000watts for the low end to get the spl level i want so i need 4 cabs for the gig. I am sorry that i argue or discuss firmly with you my point of view i am just a stubborn newbie i guess.
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CoronaOperator
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Re: Setting limiters

#19 Post by CoronaOperator »

ACUA wrote: i was under the understanding that many sound guys used wattage to calculate how much equipment was needed for venues, i have heard it said 3watts per person, or so many watts per square foot of space etc, are these things not talked about like this?
Not by anyone who understands what is going on. The difference between 50,000 watts and 100,000 watts on the same rig is only 3 dB's, 3 dB's is a barely perceptible increase in volume. The problem is that different rigs have different sensitivities (amount of output compared to the amount of input). 100 w into a home speaker might get you 109 dB's of output at 1 meter, 100 w into 4 DR250's would get you closer to 131 dB's of output at 1 meter. 131 dB's is a whole lot more sound than 109 dB's.

To cover a space, you have to know the SPL level required at what distance. Then work that level back to 1 meter, for every doubling of distance sound drops (outdoors) 6 dB's. Then you need to know the output your cabs are capable of and know that for every doubling of cabs, you get 6 dB's.

Example: if I need 110 dB's of bass at 32 meters from stack of subs (about 100 ft), then 32 meters is 5 doublings of 1 m (2,4,8,16,32), so 5 x 6 dB's per doubling is 30 dB's. 30 dB's + 110 initial dB's = 140 dB's at 1 meter.

1 dual T60 can do about 128 dB's at 1m at full power, so 140 dB's - 128 dB's = 12 dB's more than 1 dual T60
That means we have to double the cab count twice, which gives us 4 dual T60's at full power to get 110 dB's at 100 feet out. More cabs would put less stress on the system but 4 dual T60 cabs would be the minimum.
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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Bill Fitzmaurice
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Re: Setting limiters

#20 Post by Bill Fitzmaurice »

ACUA wrote: i am a generator technician by trade, generators are rated in watts, its the common term of measurement used and understood for power generation, knowing the wattage is how you know how much work is being done.
Watts only tell how much power is either available or consumed. Here's a question for you: which is brighter, a 10 watt or a 50 watt light bulb? On the face of it one would say the 50 watt bulb, but that leaves out the most important parts of the equation. Is that an incandescent bulb, a florescent bulb, a compact florescent, an LED? Infrared? Ultraviolet? What's the color temperature? You can know the watts and literally know nothing. And compared to audio gear light bulbs are simple.

CoronaOperator
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Re: Setting limiters

#21 Post by CoronaOperator »

ACUA wrote: when you plan a gig, do you not look the place over and evaluate,saying this place needs x amount of power, x amount of drivers etc,
Obviously after you use your rig for awhile you can make those assumptions based on your experience with that rig and expectations of the event. It's no different than after awhile you can gauge how much your truck can haul by looking at the load. Using a different rig would require either doing the math again or some experience with it first. Expectations of the organizer can also take some time to learn as well. I've used 4 DR250's and 2 Dual T60's to do 500 people outdoors with plenty of headroom to spare and I've used that same rig for monitors for 1 international DJ 4 feet from his head with almost no headroom to spare. How much is enough varies.
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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Re: Setting limiters

#22 Post by Bruce Weldy »

ACUA wrote: is there any situation or manufacture of amplifier that you should not run wide open on the amp?
If you have matched your amps to your cabs with some reasonable headroom, I'd say the answer is no.

As Bill said earlier, sometimes you may want to adjust the controls down....that's certainly ok as long as you have set the limiters with them wide open. Then the worst that can happen is that the balance is bad, but at least you don't blow anything.

I often will attenuate my tops in order to balance the system - even though I'd balanced it and EQed with everything all the way up. If the tops are too hot, I just peel 'em back a hair.

But, in the case of subs - they are wide open and I base everything else from there as far as balance.

6 - T39 4-25" 2-22" 3012LF
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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Re: Setting limiters

#23 Post by ACUA »

thank you everyone that really helps me out. I get it i think. I pulled the 3watts per person bit out of a book Live Sound Reinforcement by Scott Hunter Stark. i hate when i read something that i believe to be a valuable source and use it as education only to be told that its not good information... :owned:
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Bruce Weldy
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Re: Setting limiters

#24 Post by Bruce Weldy »

ACUA wrote:thank you everyone that really helps me out. I get it i think. I pulled the 3watts per person bit out of a book Live Sound Reinforcement by Scott Hunter Stark. i hate when i read something that i believe to be a valuable source and use it as education only to be told that its not good information... :owned:

The other part of the equation is the efficiency of the speakers. I see people all the time bragging about their 10,000 watt systems.....my BFM rig never sees more than 3000 at full tilt and blows 'em away. These designs are very efficient and get really loud with very little power. I run 7 XLS amps (well, one is an xTi) for my full rig with mains and monitors....all on one 15 amp circuit....outside for crowds up to 500 or more. Of course, that's for live bands - so it's a little different than a DJ gig - but it's still pretty amazing and the sound quality is great.

6 - T39 4-25" 2-22" 3012LF
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."

ACUA
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Re: Setting limiters

#25 Post by ACUA »

My ego aside that's why I am here, I believe these cab designs are the real deal. I am finding it a step learning curve as not much translates from all my prevous studies go. It causes me a ton of greaf I feel like the new kid on the block,
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Bruce Weldy
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Re: Setting limiters

#26 Post by Bruce Weldy »

ACUA wrote:My ego aside that's why I am here, I believe these cab designs are the real deal. I am finding it a step learning curve as not much translates from all my prevous studies go. It causes me a ton of greaf I feel like the new kid on the block,
Don't feel bad......I had been doing this for 35 years before I got here and learned just how much I didn't know.

And these cabs are the real deal - especially from the bang for the buck perspective.

6 - T39 4-25" 2-22" 3012LF
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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Tom Smit
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Re: Setting limiters

#27 Post by Tom Smit »

Welcome to the block, kid! Haha! Most of us have been where you are....and still learnin'. :wink:
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monekh
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Re: Setting limiters

#28 Post by monekh »

I have a feeling I've asked this before, but had a search and couldn't find it so may have been an old/deleted thread.

Long story short - first event post covid, turned on DSP to a nice 'internal battery failure' message (think it got so cold in storage the memory failed), so lost all my settings, including limiters. Thanks to this thread, and the plans, I know to use a 60Hz tone to set the voltage limit for our T60s.

Would someone be able to advise me again what frequency to use, and what voltage to set at, when setting limits for OT12s? Running Deltalite 2512s and ASD1001s, crossing over at 2kHz. I know with mids and tops it's not as crucial as with subs, and likely to hear the drivers struggling before damage occurs, but just for peace of mind...

Thanks!

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Re: Setting limiters

#29 Post by Bruce Weldy »

monekh wrote: Fri Dec 03, 2021 6:26 am I have a feeling I've asked this before, but had a search and couldn't find it so may have been an old/deleted thread.

Long story short - first event post covid, turned on DSP to a nice 'internal battery failure' message (think it got so cold in storage the memory failed), so lost all my settings, including limiters. Thanks to this thread, and the plans, I know to use a 60Hz tone to set the voltage limit for our T60s.

Would someone be able to advise me again what frequency to use, and what voltage to set at, when setting limits for OT12s? Running Deltalite 2512s and ASD1001s, crossing over at 2kHz. I know with mids and tops it's not as crucial as with subs, and likely to hear the drivers struggling before damage occurs, but just for peace of mind...

Thanks!
I believe Bill has said to use the RMS rating and cut it in half. So, that would be 125 watts at 8 ohms. That's 31 volts. Of course it always depends on excursion. The lower you have 'em high-passed, the less power I'd give 'em. If you high-pass at 100 or above, I don't think you'd have any problem giving them 35-40 volts.

As far as what frequency - anything over your crossover point - but I'd use 100. Why? Just because....... I don't have a better explanation.

But bottom line is to always be listening......you'll know if you get too far. I've never had one of my OT12s fart out.

6 - T39 4-25" 2-22" 3012LF
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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Seth
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Re: Setting limiters

#30 Post by Seth »

I don't think the test frequency matters too much, except you might want to make sure the chosen frequency is not too near the crossover frequency. Especially not on the downhill side of a filter.
Otherwise, you'll be scratching your head wondering why there's not even enough voltage coming out of the amplifier to limit.

Personally, I think putting a limiter on the tops is a good idea. Even if we never push it that far, it will keep inadvertent pops and clicks at speaker happy levels.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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