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Author Topic: JBL SRX 815P and SRX818SP Power Consumption  (Read 1130 times)

Travis Watson

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Re: JBL SRX 815P and SRX818SP Power Consumption
« Reply #10 on: November 04, 2017, 11:48:49 am »

I would bet unless you have laid eyes on the breaker, that it is a 20 amp breaker going to the wall.
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Travis Watson
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Bob Leonard

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Re: JBL SRX 815P and SRX818SP Power Consumption
« Reply #11 on: November 04, 2017, 11:49:53 am »

Luke,
 
Full "RMS" power is determined by measuring the voltage of a sine wave,  voltage x voltage /resistance ="watts RMS". A sine wave has a crest factor of 3 dB, but "full power" is considered to be that, -6 dB would be 1/4 power, still twice as much average power as 1/8 power, pink noise (12 dB crest factor) "tickling the limiters" as Chris noted.

Circuit quantity has nothing to do with low voltage "brown out", (which will generally reduce the power an amplifier can produce) wire gauge and distance to the mains transformer determine that. A single circuit run of 10 AWG 50' from the mains will be far more "stiff" (less voltage drop) than two circuits of 14 AWG running 150'.

Art

Art is correct.

Although 15amp wall sockets are common, 15 amp circuits and 14ga romex is not. Most facilities are wired using 12ga wire to 15 amp sockets because they cost less and still meet the requirement of the law. For a small system of the type being discussed two (2) circuits will do the job, as long as they are actually separate circuits.
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Chris Poynter

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Re: JBL SRX 815P and SRX818SP Power Consumption
« Reply #12 on: November 04, 2017, 11:52:54 am »

If the speakers will pull up to 5 amps  at modest use, then 4 of them at 5 amps will be 20 amps!!! A 15 amp circuit will not tolerate that draw for long before it says no more and trips.

Hi Luke,

As I mentioned, my speakers draw approximately 5A combined... as in... both of them together. And that's at peak hour with a small bass boost applied (because I don't currently have separate subs) and the limiters flickering on and off.

After hearing the various opinions on here I am fairly confident that I can add two more speakers (i.e. the subs) with the same power draw onto the same 15A circuit without any issues.

Thanks, Chris, for the point about the crossovers. That makes me even more confident. :)

Then, I'll probably put my haze and lights on the same circuit, but I'll need to do some testing with the lights first.

Thanks everyone!

Christopher Poynter
www.chrispoynter.ca
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Robert Piascik

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Re: JBL SRX 815P and SRX818SP Power Consumption
« Reply #13 on: November 04, 2017, 01:51:09 pm »

There's no really accurate way to calculate this because music is dynamic. The lights are what they are, that is easier to measure. Also, if you were to hit 15.1 amps that's not necessarily going to shut the circuit off.
The only way to know for sure is trial and error. If you are on 20 amp circuits (and you probably are) I think you'll be amazed at how much you can pull before shutting them down. I'd keep the lights and hazer on their own circuit and you'll probably be fine. If you shut it down, split something onto the light circuit and turn it down.
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Luke Geis

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Re: JBL SRX 815P and SRX818SP Power Consumption
« Reply #14 on: November 04, 2017, 10:41:28 pm »

I am not certain that running a crossover is going to save much more energy. You are still using two more speakers with essentially the same specs afterall. So 10 amps total in just speakers is still a lot. Like I said they will plug along, but you may find that on bass heavy hits, the lights will dim.

I stand corrected on power ratio. I got my digits confused obviously. My question mark was my stating my doubt. In either case the subs will draw a little more than the tops and the tops a little less than before. It will be the long sustained bass drops that will show the power sources weakness.

I go by more of a plan for the worst and expect the best type of mindset though too. No one intends to get in a car crash, or drop a board on their friends foot, but it happens every day. This is such a case where it sounds like you have an opportunity to not test fate. Rule #1 for audio is that Lights and Audio don't mix. That means keep the lights as far separated from your audio as possible. For me, if I know that I will use at least most of a circuit, I will source another one to reduce fear of anything. If you have ever blown a circuit mid show you will see the embarrassment that comes with it. I have been lucky in that I have never popped a fuse due to my own doings while doing sound, but it has happened to me for other reasons and it blows ( quite literally ). I f I know I can do a show on 2 full circuits, I am sure to ask for 4, just in case.
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Paul G. OBrien

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Re: JBL SRX 815P and SRX818SP Power Consumption
« Reply #15 on: November 05, 2017, 12:49:21 pm »

As I mentioned, my speakers draw approximately 5A combined

One thing that has not been mentioned here is that those measurements you are taking and the current draw listed in the specs are continuous not peak. Now when it comes to infrastructure power your average 15A circuit can deliver more than that for short duration peaks so this isn't a big concern, but just to put this into perspective your proposed system with 2 subs and 2 tops would not run at 100% output on a 2000w generator which math(and advertising) says is equivalent to a 15A shore power circuit, and that is because the peak current draw will exceed what the generator can supply.

The other thing I want to say is that you can expect the subs to draw more continuous and peak current that your mains, if it were me I'd budget on supplying 5A continuous per sub for full output which means you need a solid 15A continuous for the full system not 10A.
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Luke Geis

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Re: JBL SRX 815P and SRX818SP Power Consumption
« Reply #16 on: November 05, 2017, 01:58:53 pm »

I am assuming that he is also using a power strip to supply the power to his different units. Most all power strips are 15 amp rated. If it is a GFCI power strip I would be even more concerned about running 4 speakers on just only one. Another consideration is the actual wall outlet, which if it is at a business that is on the up and up, will have a GFCI outlet. My bet is the later. If not, then yes we can safely assume a 20 amp breaker in the panel. which it very likely is. I have seen old breakers that have de-rated and will pop earlier than their stated spec though. In other words, don't try and run all the way up to a breakers rating, it is just asking for problems.

I prefer to go by watts drawn. A 20 amp circuit is rated for 2,400 watts. A 15 amp circuit is rated for 1,800 watts. 5.6 amps is roughly 660 watts. So 4 speakers running at roughly 5 amps total will pull around 1,200 watts. If each speaker draws it's potential 5.6 amps, they will be pulling 2,640 total watts!!!! This is a little more than even a 20 amp circuit will handle. As mentioned this will be RMS and not peak wattage pull. This leaves very little to no window of safety.

The quick and easy test would be to run the whole PA into limiting and see how long a 15 amp breaker of any sort will tolerate it.
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Josh Rawls

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Re: JBL SRX 815P and SRX818SP Power Consumption
« Reply #17 on: November 06, 2017, 11:14:20 am »

I've used two SRX812p and two SRX828Sp along with the DJ equipment such as computer and controller on one 20amp circuit. Worked no problem at all.

As a test I took them to where the limiters were getting tickled for 30 minutes, no trip of the breaker. Power source was a 100' 12ga extension cord run to the generator spider box.

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Chris Poynter

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Re: JBL SRX 815P and SRX818SP Power Consumption
« Reply #18 on: November 06, 2017, 10:21:35 pm »

One thing that has not been mentioned here is that those measurements you are taking and the current draw listed in the specs are continuous not peak.

Thanks for your input here, Paul.

I should clarify though: The measurements I mentioned actually were peak. My power meter lets me know the peak draw at the end of the night.

I've used two SRX812p and two SRX828Sp along with the DJ equipment such as computer and controller on one 20amp circuit. Worked no problem at all.

As a test I took them to where the limiters were getting tickled for 30 minutes, no trip of the breaker. Power source was a 100' 12ga extension cord run to the generator spider box.



Thanks Josh. That's all I needed to hear! :)

_____________________________________

Just to add one more thing for everyone: I keep mentioning 15A circuits because sometimes I play older venues that have 15A circuits. Most venues have 20A circuits in their event spaces, so generally, I am running off two of those.
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Paul G. OBrien

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Re: JBL SRX 815P and SRX818SP Power Consumption
« Reply #19 on: November 06, 2017, 11:53:28 pm »

Josh how big was the generator?
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