help with impedance issue ampeg svt-II

Discussion in 'Amps [BG]' started by ripper78, Feb 11, 2014.


  1. ripper78

    ripper78

    Joined:
    Feb 11, 2014
    Location:
    Atlanta
    Hey,
    I need some help with an impedance problem. I currently run a 1990 ampeg svt-II (non-pro) through an ampeg 810. I'm about to pick up a new cab to add to my current set up, the model being an ampeg svt-1510he. It's got a 15", 10" and tweeter and is 8 ohms from what I've read online.
    My head has two impedance options: 4 ohms or 2 ohms.
    The 810 is 4 ohms and the new cab is 8 ohms.
    I don't see a way to match the cabs to the head.
    How do I safely run both cabs and on what impedance should I set the head? My 810 has two 1/4 inch output jacks (and speak-ons but the smaller cab does not so we'll ignore them)
    help?
    Here's some links to the gear:
    head: http://www.spengler-music.co.uk/SVT11300.pdf
    810: http://www.ampeg.com/pdf/svt810eav.pdf
    1510: http://manningsmusicals.co.uk/amplification/ampeg-svt-1510he-speaker-cabinet/
  2. KablesP

    KablesP

    Joined:
    Oct 29, 2013
    Set the amp to 2ohm. An 8ohm and a 4ohm cabinet together create a 2.67ohm load.

    However, I don't really feel like the 1510 will add all that much to your setup. Add another 810 :bassist::D


    I just grabbed an SVTII NP as well and I love it! Still have yet to play it through an 810, but I imagine it is glorious!!
  3. dincz

    dincz

    Joined:
    Sep 25, 2010
    Location:
    Czech Republic
    Use the 4 ohm setting. Tube amps tolerate mismatch to a lower impedance better than higher.
  4. walterw

    walterw Supportive Fender Gold Supporting Member

    Joined:
    Feb 20, 2009
    +1

    why bother?

    on top of everything else, that goofy mismatched cab being 8Ω means it'll only get like half the amp power that the other 4Ω cab gets, making it even more pointless.
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  6. KablesP

    KablesP

    Joined:
    Oct 29, 2013
    Did not know this. Thanks for the heads up :bassist:
  7. CL400Peavey

    CL400Peavey Supporting Member

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    Nov 7, 2011
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    Location:
    Grand Rapids Michigan
    +1
  8. ripper78

    ripper78

    Joined:
    Feb 11, 2014
    Location:
    Atlanta
    I want the 15" because I play sludge and want the extra lows. I've seen other heavy bassists do it and have heard/felt the difference.
    Wasn't looking for opinions on my "pointless" addition, but rather help with impedance and whether to run in series/parallel. Anyone?
  9. walterw

    walterw Supportive Fender Gold Supporting Member

    Joined:
    Feb 20, 2009
    you're assuming that a 15 cab is gonna have more lows than something else, and that's not true at all. 4 tens will usually smoke a typical single 15 for lows, along with highs and volume. you've got almost twice the speaker cone area and four times as many magnets driving it!

    if you want to drag out two big cabs for a massive wall of lows, nothing will beat a second matching 8x10.
  10. JimmyM

    JimmyM Supporting Member

    Joined:
    Apr 11, 2005
    Location:
    Apopka, FL
    Disclosures:
    Endorsing: Ampeg Amps, EMG Pickups
    Yeah, well welcome to Talkbass ;)

    To keep up with an 810, you'd need at least two 15"s, preferably 4.
  11. BassmanPaul

    BassmanPaul Gold Supporting Member

    Joined:
    Aug 25, 2007
    Location:
    Toronto Ontario Canada
    I'll second Jimmy's welcome and agree fully with his comment. Putting a single 15 in parallel with an 8x10 IS pointless. It will always be a very weak link in your system and subject to failure even at twice the impedance of the 8x10.

    A single 15 puts out about what a 2x10 can produce. If you do a search you'll find many post from folk who have mated one to a 4x10. The 15 inevitably fails. To work safely with a 4Ω 8x10 you would need a 4Ω 4x15.

    The thought that a larger cone equates to more lows is simple tripe. If it did, how would PJB cabinets produce any lows at all? Their drivers are 5".
  12. catgut

    catgut

    Joined:
    Jan 15, 2014
    Location:
    Seattle, WA
    True true. I have single 5" drivers in my hi-fi that reach 28-30Hz. The 8" and 10"ers before only got 45Hz or so. Construction, tuning, air, all matter.
  13. RickenBoogie

    RickenBoogie

    Joined:
    Jul 22, 2007
    Location:
    Dallas, TX
    Yes, you're getting good advice. Maybe not what you wanted, but solid advice nonetheless.

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