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Qusstion about Powering an Extension Cab?

Discussion in 'Amps and Cabs [BG]' started by Whitey, Feb 11, 2002.

  1. Whitey


    Jan 8, 2002
    Beckley, WV
    If I purchase a Fender BAssman 25 which has an extension speaker out jack and saids that you can like run a cab off of the combo also; how would the cabinet sound with just the 25 watt bassman powering it? Would my volume increase? Would the bigger speakers mean that it could carry the volume without distorting at maximum volume? Thanks
  2. Hmmm....i have a response that is relevant but probably not exactly what u wanted...

    I just bought a Crate GFX15 amp for guitar. One thing I did to test it was to see if it could power a 2X12'' Mesa Cab that was available. It actually powered the Mesa cab well, especially on the distortion channel. So my thought is that you could definitely power a 2X10'' bass cab with a Fender Bassman 25.

    For a general rule, it has been said (not by me) on this forum that doubling your speaker quantity doubles your headroom, just as doubling the wattage does. That said, since sound volume in decibels is logarithmically related to the sound intensity:

    dB = 10 log (P/P_ref), where P_ref is the reference intensity referred to as the "threshold of hearing", P is the intensity, and dB is how loud something is in decibels. (For reference, 120 dB is the threshold of pain and 110 ~ a rock band at 2 meters away, so WEAR UR EARPLUGS :D )

    So, a 100W head with 2 4X10'' cabs is capable of having equal volume with a 200W head pumping through one 4X10'' cab.

    To answer your second question, a higher wattage head distorts later than a lower wattage head. For example, using guitars (I know guitars better) a MEsa Dual Rectifier head (100W) will distort quicker at high volume than a Triple REctifier will (150W). The same idea happens with basses. I am not sure if adding a cabinet will help this, but I think it will.

    Hope this helped.
  3. bizzaro


    Aug 21, 2000
    It is my understanding that anytime you increase cone area (add another cab) you will increase your volume. If you don't have the power to drive it I don't know what happens. Wish I could be of more help. 25 watts for bass is pretty marginal in any situation.:)
  4. SRSiegel

    SRSiegel Guest

    Sep 17, 2001
    Ann Arbor, Michigan
    im not exactly sure, but this might be a case where you would be underpowering the cab. i would not add an extension cab that was any more damanding than the stock speaker in the combo. if you try to drive a demanding cabinet like say, any decent 210, you will most likely clip the poweramp, and hence you might danage/eventually blow the speakers. i could be entirely wrong, but i wouldnt put anything than another small, single driver cab on that amp.
  5. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    Read the manual first!!!!

    A lot of small combos have an internal 4 Ohm speaker, which means you can't add another cab.
    You can only use another cab INSTEAD of the internal one.
    If the internal speaker is an 8 Ohm speaker you can add another 8 Ohm cab, though.

    25W won't get you far anyway, even with an additional cab.
    Underpowering can be a problem too. A 25W amp will distort quickly and can destroy the speakers
  6. According to the Fender site, connecting to the external speaker jack disconnects the internal speaker.

    Yes - you can run a cabinet from it.

    If you connect a good cabinet it will sound good - up to 25 watts.

    Most likely, any cab you connect will be more efficient than the internal 10 so yes, it should be louder. It will also be louder because the external cab will probably handle the lower frequencies that the 10 can't handle. With the 10, this is just wasted power. With a 15, for example, this will be increased volume.

    If the distortion is caused by clipping the amp, no, you will not get rid of the distortion at max volume.

    If the distortion is a rattling speaker, then yes.

    One more note: The Fender site does not state the minimum impedence for the amp. Most solid states will go down to at least 4 ohms. If the amp will support 4 ohms, then a 4 ohm cab will also cause the amp to deliver more power.

    To summerize, I would expect that amp would be quite a bit louder with a 15" bass cabinet, for example, than the internal 10, even more so if the amp supports 4 ohms and you use a 4 ohm cab. It's not going to be an earth-shaker though.
  7. He wouldn't be underpowering the *cab*, because there's no such thing, really. Cabs don't "demand" power in any real sense; they either accept it gracefully or they don't.

    But he definitely would be underpowered for almost any gig I can imagine. It doesn't matter much which cab he tries to use as an extension--he will likely get a modest increase in volume, but 25 W just isn't much for bass under any circumstances.
  8. I agree. I would go with an absolute minum of 100W in a small gig situation, but then again, what do i know :D

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