power draw

K, KW, and KLA Series loudspeakers

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Mon Dec 28, 2015 9:59 am

  • On a 24ov supply, what is 2 x k12 and 2 x kw181 going to use in amps?
    I,m assuming a bit more involved than i =p over v
    paulpa
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Mon Dec 28, 2015 10:25 am

  • What exactly is AC Power Consumption (1/8 Power): 230 VAC, 1.13 A is that (an occasional clip light flashing) i.e pretty loud
    is having these 4 on one supply advisable with lighting and mixers etc?
    In UK the ring main should be 32 amp fused but the plug fuse that they all go to via multi adaptor is 13 Amp

    I,d imagine lighting/mixer using up to 2 amp
    paulpa
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Tue Dec 29, 2015 9:52 am

  • With four of them on 240V, you can figure the worst-case current demand will be around 4.5 A total.

    Next, determine what the rest of your kit needs, and add it all up. Compare that total with what's available.
    Bob Lee
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Thu Dec 31, 2015 9:34 am

  • Thanks, ok much better than i thought so i should be fine with them on one 13 amp protected extension fully un wound
    paulpa
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Mon Feb 15, 2016 6:51 am

  • Allowing 4.5A total seems a bit low. For 1/8th power (ie, pink noise, 9dB peak-to-average, just nudging the limiters), its about right. However...

    If you're playing seriously compressed music that contains sine-wave-like content, your power draw could be much higher.
    Check out this track (warning - lyrics aren't safe for minors/work/sensitive ears): https://www.youtube.com/watch?v=UnQY3swM4tA
    At around 1 minute in, a 36Hz compressed sine wave hits and just stays there. If you're nudging the limiters on the KW181, the amps will be putting out some serious continuous power. Lets say the KW181 will do 1000W continuously into its 18" driver, that's about 4A draw (plus a bit for amplifier inefficiencies etc, but we'll ignore that) per subwoofer, so 8A total. If the tops are also playing along, you might be looking at a more typical power draw of 1A from those, so your PA will be pulling around 10A with that track playing at full volume.

    Of course, not all music is as demanding as that track. I picked it because its the most abusive track I can find in terms of making amps/speakers/circuit breakers work hard. There's more like it, but it is a fairly particular genre that won't appeal to everyone.

    As with all things sound-related, headroom is a good thing. If you've got to run off a single 13A socket, don't bring 8.5A worth of lighting only to find the first track you play demands more of your system than the test noise - you'll blow a fuse and that's no fun.

    Some manufacturers put 1/8th power and 1/3rd power draw specifications on their datasheets. The latter is there to represent the worst-case current draw, and should be used if you're going to run the system hard with particularly demanding program material.

    Chris
    chris661
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Mon Feb 15, 2016 10:03 am

  • In theory, that is true for a heavily compressed signal in an undersized system that will ultimately suffer from serious power compression in the drivers. In practice, the 1/8 of full power current demand represents a realistic worst-case situation.
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Mon Feb 15, 2016 10:54 am

  • When low-pass filtered at 100Hz, that track has a peak-to-average ratio of just under 3dB, so rating for 1/2 power draw instead of 1/8th would be more representative of the worst case use, in my opinion.

    To take some numbers from the RMX4050HD spec sheet,
    For a 4ohm load, 110v supply:
    1/8th power current draw = 10A
    Sine wave *just* clipping = 42A

    Sine waves also have a 3dB peak-to-average ratio, so I'd expect an RMX4050HD powering 4ohm subs with that track at full power to draw somewhere around 40A (assuming the cabinet impedance is 4ohm at the frequencies of interest).
    Similarly, I'd expect a KW181 to draw around 4A with the limit lights *just* coming on.

    Again, this track is an extreme example, and most popular music won't present a problem. Live music has a particularly wide dynamic range, so current draw will be even lower.

    Chris
    chris661
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Mon Feb 15, 2016 3:53 pm

  • It's sort of a different world with powered loudspeakers versus separate amps and loudspeakers. With separates, if you're going to operate the amps in such severe ways, you can also select loudspeakers uprated accordingly to avoid power compression and, ultimately, driver failure.
    Bob Lee
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