1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  

Power Matching Head and Cabinet (SWR)

Discussion in 'Amps and Cabs [BG]' started by kidhominid, Dec 13, 2006.


  1. kidhominid

    kidhominid

    Dec 13, 2006
    Hello guys,

    I just bought a SWR Bass 750 head and one SWR Goliath III cabinet
    (8 ohm). If you are familiar with the SWR Bass 750, it is 450 watts into 8 ohms and the cabinet is 8 ohms and rated at 700 watts.

    Now, I've heard that it isn't good to have you amp power be way below the cabinet's rating and that this stresses your amp. Is this true?

    I played tonight and found that the amp got super hot! Is this a sign of the amp working too hard? How should I remedy? I don't have room for a full stack, so maybe I should get another, lower wattage cabinet?

    Please lend a brother some advice!

    Thanks!
     
  2. Headroom

    Headroom

    Apr 5, 2002
    I think everything’s probably cool (so to speak). The amplifier case is hot because it's doing it's job, as designed, to wick-away heat from the internal components. 450 watts should be more than enough to power that cab. It’s sensitivity is 105db so it should be fairly loud.
     
  3. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Not necessarily. Warm is OK, it's supposed to do that, but if the case is too hot to leave your hand on it I'd install a fan. As for the 105dB rating, that was probably measured at 2.5kHz. The website says it's -3dB at 40 Hz, inferring 102dB sensitivity at 40 Hz. No five cubic foot 4x10 is capable of that spec; 90dB at 40 Hz would be realistic.
     
  4. Hello.... cabinet power rating has nothing to do with how hard an amp works.... no problem there.

    The SWR line (at least the older ones) used the metal sids and top of the the head as a heatsink (versus the fins, etc. used on some amps). So, they will feel warm, and can actually get very hot. So, I don't think you have a problem there.
     
  5. Jim Carr

    Jim Carr Dr. Jim Gold Supporting Member

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    I believe the 750 has a defeatable fan. The fan switch is next to the power switch on the front panel (assuming it has the same control layout as the SWR 350).

    Be sure that the fan is switched on (same position as power on, I think). Check the manual (there is an online pdf) to see for sure which position is on. If you don't get any fan action after a few minutes of playing at a medium high volume, I would have it serviced.

    These do get very warm. :ninja:

    About the power: if it is loud enough, you are fine. If it isn't, then get more power. Sorry to be so simplistic, but that's really all there is to it. You won't hear the amp clipping if the limiter is engaged (a push-pull on the effects blend knob, where in is engaged). The preamp will audibly clip (turn it down if it does). There is also a "clip" light, as I recall, on the power section. That light will let you know that the limiter has been activated. :cool:
     
  6. kidhominid

    kidhominid

    Dec 13, 2006
    I think some of the later SWR 750 models had a built-in fan. Mine does not. Should I put a clip-on fan in the rear of the unit to help or does the heat not really pose a problem?
     
  7. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Heat degrades just about every component in the amp, right down to the PCB boards and control pots. If the case is getting hot the innards are probably hotter, so I'd do the fan. If there's a spot where it can vent the chassis that would be where to put it. If it's an old amp blowing all the accumulated dust out of it is a good idea too.
     
  8. Triclops

    Triclops Guest

    Jan 14, 2006
    buy a 4 ohm goliath junior III perhaps...your sound will never be better! and the heat issue is not a big deal with these heads...if to hot get a fan. this head will safely give 850 watts at 2.6 ohms, so get a 8 ohm, and a 4 ohm cab and plug your ears!
     
  9. Jim Carr

    Jim Carr Dr. Jim Gold Supporting Member

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    [​IMG]

    Does it look like this? N.B., fan switch is on the right, next to the power switch. They both are partly red and black rocker type. :D
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.