Amp Hookup

Discussion in 'Microphones (live or studio)' started by Codemonkey, Nov 20, 2009.

  1. Codemonkey

    Codemonkey Well-Known Member

    Dec 11, 2007
    Scotland, UK

    Let's say I wanted to hook up a pair of 8-ohm (400W peak/200W RMS) speakers to a 2 channel amp (it's a Phonic Powerpod 740) that delivers:
    145W per channel at 8-ohm
    220W per channel at 4-ohm
    440W bridged at 4-ohm

    If I were to put the speakers in parallel on the bridge, are there any drawbacks? The amp will be OK running at 4-ohm, however it may be in a relatively warm place. But it won't be cranked, so I doubt it'll burn.

    The very same amp has been pushing two smaller (300W) cabs at 145W each and is plenty loud enough. However with the larger (400W) speakers the volume is of course different. Can't remember if they're louder at the same settings. (I assume the sensitivity is different).

    What do you reckon is the best?

    BTW: it's used for a little bit of vocal amplification, but mostly for music/sound effects. Easy 2-hour theatrical job.

    There's one alternative, which is to hook both up in parallel on a 500W (4-ohm) amp, and run a cable the full length of the hall. But I'd rather not.

    Also, phantom power won't fry a passive DI box, will it? I don't think so but I'd rather not chance it.
  2. Spase

    Spase Active Member

    Feb 21, 2006
    The amp is fine bridged with the speakers in parallel(a fan might be a good thing if its hot there). If you run a long cable you'll be changing the Ohmage of the run, it would depend on the distance and gague of the wire, but that's probably not a big deal unless it's pretty long. The Phantom power should not be an issue on the passive DI.
  3. stealthy

    stealthy Guest

  4. bent

    bent No Bad Vibes! Well-Known Member

    Oct 26, 2007
    Cocoa, FL
    Home Page:
    Good, but just to reiterate what I've said before about this:
    Don't crank the amp. Ever. Crank it up at the mixer.

    Gain structure my dear monkey!
  5. Codemonkey

    Codemonkey Well-Known Member

    Dec 11, 2007
    Scotland, UK
    OK thanks for the amp/PP info. Gets something off my mind!
    (Of course, I can't run the passive DI now because I don't have enough returns on the snake!)

    It's not me who's running the mixer ... or I wouldn't be worried about having TWO HOURS to set all this uptomorrow. I'd have all night to tweak it, but no.. I'm onstage wearing a pimp jacket and pretending to know my lines.

    The thing about the "amp" is that it's really a powered mixer, and it's also going to be sitting under a 1U amp and a snake stagebox**. I'm SERIOUSLY tight for space because of all the freakin props.
    Also, surely if you crank more signal through the input, it'll be pushing more through the output so the power consumpation (and heat generated) rises anyway?

    ** guess what? The snake is about 1 foot too long. Or should I say 10 feet too short to be flexible? And it's a 12-4, with only 12 connectors on the fan. The returns are numbered "9-10-11-12" and only 11/12 are properly wired for returns. I swore a lot (under my breath) when I found that out, I'll tell you.
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