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Help with SM 400 and Isovent cab...

Discussion in 'Amps and Cabs [BG]' started by amanita, Sep 11, 2004.

  1. amanita


    Sep 11, 2004
    I have an sm-400 and an ampeg isovent cabinet. for those of you who are unfamiliar with the cab it has 2 10s on top and 2 15s facing each other. My question is this... does anyone know how many watts this cabinet is. and if so how is the best way to hook this all up. for some reason I am having trouble hearing this setup over a sunn concert lead with marshall 4x12. I know this can't be as loud as this goes....
    any help would be great. thanks
  2. Fealach

    Fealach Guest

    Apr 23, 2003
    Gone to a better place
    I am not at all an expert or particularly well informed, but I have had an Isovent for many years.

    I don't remember the stock watts of mine, I have changed the speakers, but I'd guess 600 or so anyway, from all those speakers, more if you have the "pro" version which had better speakers. It's not here with me, but if memory serves there is a full range input jack, a biamp high jack and a biamp low jack. You should be using the full range jack unless you are biamping, I do not know if your head supports this feature. If you are plugged into only one of the biamp in jacks, you are using either the top or the bottom of your cab, not both. If you are plugged into the correct jack on the amp, and your amp is set to the proper ohm load, there may be a problem.

    However, it is possible that everything is functioning perfectly. In my experience SWR amps are not loud. I owned a 900 watt SWR that was not loud enough to keep up with the band. My Isovent, even with the stock speakers, was more than enough when powered by a Mesa Boogie 400+, that's ~300 tube watts. Your amp may just not be powerful enough to get this cab to those volumes. However, my isovent was the cheaper version, with less hardy 15s than the Pro version, and playing at loud rock concert volumes I blew one while it was under warranty, which Ampeg replaced. I kept the cab, but eventually replaced all the speakers with Eden 10s and EV 15s. Now nothing can keep up with it. I think the design of the cab is innovative, and I am always looking for another, even if I would eventually replace the speakers.
  3. cb56


    Jul 2, 2000
    Central Illinois
    I had that same cab for awhile. Heavy little booger isn't it? Using the full range input is the way to go. I still had trouble hearing myself on stage with it cause all I was hearing was the 2 10's. The 2 15's(clamshelled wired out of phase) sounded great out on the dance floor but on stage it was weak sounding. I traded it in after a few months. Just my 2 cents worth of input.
  4. amanita


    Sep 11, 2004
    fealach- I am thinking of going with a henry the 8 x 8. however I may still opt to change out the speakers on my isovent. did you wire the cab to have the 15's out of phase. also what is the power rating of yours now? I think this would be better if i fixed the cab. someone took a bunch of screws out of it before it became mine. I like the design but it seems like it can't keep up with the sm 400.
  5. Fealach

    Fealach Guest

    Apr 23, 2003
    Gone to a better place
    I wasn't sure how to do the wiring, I had my brother do it, he wired the replacement 15's the same way the stock ones had been wired. My cab is now somewhere around 1000+ watts, and it is now 8 Ohms instead of 4 when run full range. I have it and a Mesa 210 that I run together with my 400+, it is phenomenal. My Iso is the only cab I have that could handle the Peavey Classic 400 (400 watts all tube) head I had.

    That said, you might want to try an 8X8 if you can take your head to a store and plug into one. Excellent sounding cab, super lows, I have one that I am selling locally (I have too much stuff and need to sell some off, and it will bring a better price than the Isovent). It's a low wattage cab. 480 I think. If you are happy with your head I think the Henry might be a better match, being closer in wattage. In my (limited) experience SWR amps seem to work best with SWR cabs. I briefly owned a 900 watt Mo'Bass, it was fine at the store through SWR cabs but it was sadly quiet through the Mesa cabs I had at home at the time.
  6. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    That should be an SVT-50 either DL , HE , or PRO.

    The PRO has cast frame 15s and celestion 10s,
    the HE has eminence everything

    All were rated at 600W.