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Question on head & cab volume

Discussion in 'Amps and Cabs [BG]' started by mattvon, Feb 13, 2006.


  1. mattvon

    mattvon

    Jan 22, 2006
    Minneapolis, MN
    Hey everybody,

    I've recently started playing bass again after a 10-year layoff and was fortunate enough to get a head & cabinet from my brother (a great player who's raising a family instead).

    He gave me his early-90s SVT II and his SWR Henry the 8x8 cabinet. Both of these had been sitting in his garage in sub-zero degree weather for over two years, and he was worried the head needed tubes in any event.

    After letting the rig get warm we both decided it was MUCH quieter than those 300w should be, so I took it in to my local repair shop and had it totally retubed, biased, and generally cleaned up and gone over. $400 later (!) I got it back with a clean bill of health and the assurance that it was hitting 300w now.

    So (you can probably see this coming) I get it home and while the tone is significantly better, it's no louder. Both the head and the cabinet are running at 4ohms, so I'm assuming that's not the issue. I don't have another cab to test it out with, but I do have an early 70s B-15s (60w) which seems obviously louder at the same volume position (ie "11 o'clock")through the same bass/signal path. Not very scientific, but...

    Sorry about the lenth of this post, but I'm somewhat stymied. Is it possible the cabinet is fried? It's not distorted at all, doesn't appear to have any blown speakers, it's just quiet.

    Thanks in advance for any suggestions, advice, etc...
     
  2. Herman

    Herman

    Dec 25, 2005
    Lynchburg, VA
    What is the B-15s that you mentioned - is it an amp?
     
  3. Groundloop

    Groundloop

    Jun 21, 2005
    Toronto
    Bummer. That combo should be making your pants flap.

    My guess would be that the 2 years in the cold may have caused the speaker surrounds (the foam/rubber bit that attaches the cone to the basket) to harden and lose their flexibility.

    Before you take any drastic steps like reconing, or replacing the speakers, keep trying to borrow (or rent) another 4 ohm cab, like a 4x10, to compare volume levels.

    Hopefully the experts like billfitzmaurice or tombowlus will see this thread and chime in.
     
  4. mattvon

    mattvon

    Jan 22, 2006
    Minneapolis, MN
    Thanks for the replies.

    @ Groundloop: I hadn't thought of renting a cabinet, that's a great idea.

    @Herman: The B-15s is/was an Ampeg Portaflex combo. 60w of tube power & preamp with a single 15" CTS (in mine) speaker. Great tone. They differ from the B-15N in that they use the V4B preamp circuit, so it's a little more "70s" sounding than the classic Portaflex sound, but it's very similar.
     
  5. Herman

    Herman

    Dec 25, 2005
    Lynchburg, VA
    OK. So is it possible to drive the speaker in your B15s with your SVT as an experiment?
     
  6. mattvon

    mattvon

    Jan 22, 2006
    Minneapolis, MN
    Hmmm, another good idea. The SVT is only switchable between 2 and 4ohms, while the Portaflex cabinet is an 8ohm speaker. I guess I could for a little while, though I don't usually underload my amps.
     
  7. Herman

    Herman

    Dec 25, 2005
    Lynchburg, VA
    From the SVT II manual:

    "Always keep the total speaker impedance at or above the rated load."

    I'd set your amp to 4 ohms and give it a shot to see if you get good volume from your B15s' speaker when driven by the SVT.

    If you do, then there's either something wrong with your SWR cabinet (as someone else speculated) or it could be just a very inefficient cab. SWR lists the sensitivity (efficiency) of your cab as "N/A". Well, I'm pretty sure that it has a sensitivity (as does any speaker) and it's definitely applicable so why wouldn't they tell you what it is? Could be that it's a very low number but that's just a guess on my part. I'm sure there are others with first hand experience with this cab that could give you more accurate info.

    Good luck.