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SVT-3 Pro and impedance

Discussion in 'Amps and Cabs [BG]' started by MattyN, May 30, 2003.

  1. MattyN


    May 26, 2003
    Seattle, WA
    i have an Ampeg SVT-3 Pro and i run it through a single Bag End S15-D.

    i'm thinking of getting a second cab but i'm worried cause i know this head has a rep for being a bit underpowered. i get plenty o' power through the 1x15.

    this boils down to an impedance question for me. yes, i know there are many threads on this subject but, hey, i'm still confused... :confused:

    1. the head puts out either 4 or 8 ohms.

    2. the cabinet is rated at 8 ohms by itself or 4 ohms if its paired with another 8 ohm cabinet (i think, please correct me if i'm wrong here)

    so... if i get a second 8 ohm cab, they will both have an impedance of 4 ohms and my set up will be louder because although there are two cabinets to power - they are less "impeded" ??

    is this a logical assumption?? this stuff boggles me.


    Dec 28, 2002
    you are right 2 8 ohm cabs will bring ya to 4 ohm and use everything that amp was ment to push...
  3. I also have the SVT-3 Pro and this amp has a few setups:

    > one 4 Ohm Cabinet gives you the 4 Ohm powerload from the amp (450 watts)

    > one 8 Ohm Cabinet gives you the 8 Ohm powerload from the amp (275 watts)

    > two 8 Ohm Cabinets give you the 4 Ohm powerload from the amp (450 watts, with each cab getting 225 watts).

    It's simple as that :)

    just see that you don't underpower your cabinets. that's bad for the head!!
  4. MattyN


    May 26, 2003
    Seattle, WA
    i feel dumb asking... but how do i make sure that i'm not underpowering the cabs?

    also, which of the setups mentioned by Phyrexian
    is likely to be the loudest?
  5. rok51

    rok51 Supporting Member

    Sep 2, 2002
    Crawfordville, FL
    Loudest would be two 8 ohm cabs...assuming they all had the same sized drivers. I, too, have an SVT III Pro (since 1994). I have used it with one 410, one 115, two of each and a combination of each. Mine sounds best with a 410/115 combination. Really like the amp. Yes, it seems underpowered for the rating, but it has never been not enough and has always sounded great. Did I mentioned it's never crapped out in almost a decade?

  6. Ziggy


    May 9, 2001
    Orange County, CA
    Rok puts it into perspective... the two 8ohm cabs - connected in parrallel, would drop your impedance to the Ampeg's minimum 4ohms. The same as the single 4ohm cab, but atleast double the speaker area moving the air. Make that second cabinet a 4x10, as Rok indicates and my personal fav setup as-well, and you've increased 'that area' to 55". (nearly 4x the 1x15 cabinet)

    As for making sure you don't 'underpower' the cabinets??.. just be careful not to drop the impedance below the recommended 4ohms minimum. The excessive demand on the head will almost surely cause it to overheat and shutdown, if not burn itself out.

    michael s.
  7. MattyN


    May 26, 2003
    Seattle, WA
    i really appreciate your advice everyone...
  8. Currently I'm using only one 8 Ohm cab (Peavey 410TVX). It's not as loud as I want it to be, but it's okay for now.

    I might ad another cabinet (4x10 or 1x15) to have more volume. Two cabinets move more air and thus sound louder.

    Underpowering: don't use the SVT-3 Pro to drive a 1000 watt cabinet (8x10?)... the amp only has 475 watts so driving a 1000 watt cab won't be good. The SVT will have to work too hard to move the speakers.