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Ampeg B25 B 2x15 cabinet?

Discussion in 'Amps and Cabs [BG]' started by hublocker, Apr 8, 2009.

  1. hublocker


    May 17, 2007
    I've got this Ampeg B25B cabinet with two 15-inch speakers in it.

    I bought it used in 1977 but it's sat unused in my basement for 20 years.

    I'm dragging it to my practice place tomorrow night, but in re-examining it I've got some questions.

    When I got it, it had an XLR female input hole plugged with wood filler and an ordinary 1/4-inch phone plug receptacle installed.

    The plate says 16 ohms, so I opened it up and rewired it for 4 as my V4B has a 4 ohm setting. But what I know about electronics you could write on the back of a postage stamp, so I don't know if I did it right.

    My trusted friend/sound man with the P.A. will figure that out.

    When I bought that cab in 1977 I was told it had been a P.A. cab.

    Did Ampeg make P.A. gear?

    I'm just wondering if the B25B was in fact a bass guitar amp cab to start with.

    Designated a B25 B, you would think so.
  2. nysbob


    Sep 14, 2003
    Cincinnati OH
    And your thinking would be correct.

    The guy who had previously probably used it for PA cab, so it magically became a PA cab.
  3. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    So, I would assume that each speaker is 8 ohms, and was wired in series for the 16 ohms, and all you had to do was rewire them parallel, for 4 ohms, yes? The B25 head was a funny critter, running at 16 ohms. I had one for a vey short while, but not the cab or I would've kept it. Great tone. Should sound killer with the V4B.
  4. hublocker


    May 17, 2007
    Oh it did sound killer when I was using it in a cover band in 77- 83. Stones, Eagles, Beatles, Linda Ronstadt, Loggins and Messina stuf, etc. I had a Rick 4001 at the time played with a pick.

    Filled community and banquet halls with bass. I didn't really understand the output/ohm load thing then and just used it set at 4 or 8 ohms output into the cab as is.

    Years later I read up on that stuff and decided to rewire the speakers to 4 ohms.

    I hope I didn't bugger the amp up.
  5. Bassmec


    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    What speakers did it have in it?
    any photographs would be handy!
    I have a very old pair of Ampeg 115's that where fitted with alnico magnet Altec Lansing 418 Series 11 musical instrument speakers.
    Wow do they sound good!.
    You probably have CTS in there, they are great too!.
    If on the other hand you have Altec VOICE of the Theatre drivers then they must be PA right!.:meh:
    If you connected the two drivers in parallel and in phase you are good to go at four ohms.:D
  6. Here is one on ebay...is it the same as this?

  7. hublocker


    May 17, 2007
    Hello Bassmec.

    I haven't had the back off in 20 years.

    We'll see next week what speakers it has.
  8. Oren Hudson

    Oren Hudson Supporting Member

    Dec 25, 2007
    Gastonia, NC
    Originally those cabs had an ohm switch at the jack, switchable between 16 and 8 ohms. No doubt when the jack was replaced, the switch went with it. Best to get your sound guy to check the ohms and wiring for optimal results. :cool:
  9. hublocker


    May 17, 2007
    Sleepy Monkey.

    Yes, that's just like my cabinet.
  10. michael_atw


    Feb 28, 2009
    Jamestown, NY
    I see I'll be rehashing this thread but I recently opened up a B25B cab (early 70's it looks from the outside) I have owned for a couple years but never ate into (I wanna sell it now). I'm wondering what speakers came stock with it? This one has Altec Lansing 418B's in it.
  11. Oren Hudson

    Oren Hudson Supporting Member

    Dec 25, 2007
    Gastonia, NC
    Standard speakers were CTS. Optional speakers were Altec 421A. :cool:
  12. michael_atw


    Feb 28, 2009
    Jamestown, NY
    Where do 418B's fall in?
  13. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    Non-stock replacements. The 418B specs are listed on this page if you're interested. Frequency response looks decent, but power handling is fairly low (100 watts), though this is probably about the same as or higher than the original CTS anyways.
  14. michael_atw


    Feb 28, 2009
    Jamestown, NY
    What would you say about them? Very good? Excellent? What might be a street value for one?
  15. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    No idea, never tried/heard them. This might help you though. Definitely seems like they're most used in guitar cabs than bass based upon the info I've been seeing in some of these threads...
  16. michael_atw


    Feb 28, 2009
    Jamestown, NY
    Very interesting. I just found a PDF from an old Ampeg B25 catalog that states that Altec 418B's were a stock option (I can't figure out how to apply a link since the google page goes straight to a PDF download). Maybe this specific cab was a 1969-1970 mate for a B25 (which was a guitar head, if I remember correctly) and the 418B's were options to make the B25 cab a guitar cab?
  17. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    The only old product literature I have mentions Altec 421s but not in the context of the B25 cab so I can't say for sure if they were available as a factory upgrade. They were using altec speakers in the 70s so it's possible, but either way whatever else I've found about the 418Bs seems that people don't use them for bass, mostly just pedal steel and guitar.
  18. jumbodbassman

    jumbodbassman Gold Supporting Member

    Dec 28, 2009
    Stuck in traffic -NY & CT
    Born Again Tubey
    for a while i used 2 of those cabs with a V4B around 73. The cts speakers were very weak but 4 of them moved some air. eventually replaced them with a svt bottom and then a second cab - V4B and SVT head
  19. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Ampeg used 418b's before the 421a's. It could easily be stock speakers in there.
  20. bryanspkr


    Mar 25, 2011
    I bought my first bass amp in 1976. An ampeg V4B and a 2-15 (closed) cab. It was used when I bought it. Had at least a few years wear. Silver nobs. Removeable cabinet dolly. Best amp I ever had. I believe the cab had altecs. I am sure it was not a b25 cab. 100%. Yet I can find no other cab model with this configuration. I think it was labeled B50. Its driving me crazy. Anyone have any info?

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