Power amp questions

Discussion in 'Amps and Cabs [BG]' started by djphil, Nov 23, 2003.

  1. Hey guys,

    If I'm running two JBL 2x15 towers w/ horns, and each cab handles 450 watts @ 4 ohms, what type of power amp would I need to run these correctly? I know power amp stuff is different than true bass heads, so I was just curious.
  2. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    One that can handle a 4 ohm load on each channel...nearly all solid state power amps.

    Power wise, I'd go with 500 to 1000 watts per channel.

    Lot's of great choices out there that would fit the bill...
  3. Ok, thanks. I guess where I get confused is how power amps have two separate channels that push a correct ohmage load, while bass heads only have one usually, and you have to match the cabs accordingly.
  4. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Hi dj, there's several different ways you can go with those. One way would be to run them in parallel, in which case you could push at least 900 watts but you'd need an amp that can handle a 2 ohm load. There are amps like that, a lot of the Stewart's and QSC's and Carvin's can do that. You could also run them separately from the two halves of a stereo power amp, in which case as you say each side can push at least 450 watts at 4 ohms. Your "effective power" might still be 900 watts, depending on how the speakers are arranged and where you're playing.

    One question, are these actually bass speakers? 'Cause I'd be very careful pushing a bass through them if they're not (especially a five string). A big solid state power amp can deliver huge bass transients that would fry most PA or guitar speakers. If you raise the power gradually, you'll probably be able to hear the point at which they start complaining. JBL's are good reliable speakers if they're not pushed too hard.
  5. Well I think we decided to get a Crown or QSC that pushes around 1400-1500, so we can get about 700-750 per 2x15 speaker cab.

    And no, they're full-range JBL speaker cabs with 2 15" speakers and a horn. We're also adding a JBL 18" sub that will have it's own dedicated 600 watt amp, and everything will be run from a Mackie CFX16, their pretty decent 16-channel mixer. I know a decent amount about this kind of stuff, and we're adding a crossover possibly, but when I go through the system it will just be for sound reinforcement. My Mesa setup is so damn loud I could play against most PA's and still win out, so it'd just be to add some texture to the sound coming from the full-ranges.

    Yeah, I know what you mean about frying stuff- my Spector NS5CRFM is sooooo hot, signal-wise. I always have to watch it when I'm not plugging into my Boogie M-Pulse 600.

    And since I'll just be going direct (if I like my SansAmp BDDI) or miked (if I sell the SansAmp if I don't like it and just get a Shure Beta 52), I can just adjust how much bass actually needs to go through the mixer and speakers, which doesn't need to be a whole lot if any. But we'll see. I was mainly just asking about correctly powering the speakers w/out screwing them up, and the tech guys at JBL gave my guitarist the rap about "underpowering your speakers" and all that BS, so he was trying to get 900 per channel, but then I heard from some other peeps that they replaced speakers and drivers on a monthly basis b/c their power amp pushes double the speaker load. So, we don't wanna do that. 600-750 would be tops, I think.