Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

Ext. cab with too low impedance

Discussion in 'Amps and Cabs [BG]' started by Quzumm, Oct 26, 2000.


  1. Quzumm

    Quzumm

    Sep 25, 2000
    Trondheim, Norway
    I'm planning to buy a 4*8 cab (4ohms) and use it with my combo. But, the manual for the combo says that the minimum impedance of a cabinet connected to external speaker socket must be no lower than 8 ohm.

    (Cabinets don't grow on trees where I live, at least not 4*8's, pluss I'm going to get this cab cheap. So I'll "have" to get THIS cab..) :)

    My question is: If I use the 4 ohm cab, is it going to cause damage the combo or the cab, or is the cabinet just going to get more/less power than the speakers on the combo?
     
  2. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    Yes, you can damage your amplifier by going lower than the rated impedance.

    You can try rewiring the 4-8 cab to be 16 ohms (my guess is it has four 16 ohm drivers inside). Good luck.
     
  3. You will damage the amplifier. Any more than 8 ohmes and it will be alot quiter than the combo speakers. So you should give it a miss.
     
  4. Quzumm

    Quzumm

    Sep 25, 2000
    Trondheim, Norway
    Okay then..
    Thanks for the help. :)
     
  5. Munjibunga

    Munjibunga Total Hyper-Elite Member Gold Supporting Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    However, if your combo is the type that you can easily unplug the combo speaker from the amp (like many Hartkes), you could just disconnect the internal speakers and plug in the 4x8. I have a friend who does this with a Hartke 1155, which has the 3500 head in it, and plugs it into his Eden D-212XLT. Sounds mucho mas bitchen, I must say.
     
  6. Quzumm

    Quzumm

    Sep 25, 2000
    Trondheim, Norway
    Not possible..
     
  7. In that case, you're probably better off just selling your combo and getting a good used 300W-4ohm head, maybe an Eden WT-300, SWR Bass 350, Trace Elliot AH300-7...
     
  8. Quzumm

    Quzumm

    Sep 25, 2000
    Trondheim, Norway
    Still the same cabinet..
    The cabinet is "selfmade", and the person who is selling it is not so sure if it's 4 or 8 ohms, but now he thinks it's 8 ohm... Is there any way to check this out, without having to open the cabinet?? Will the amp get damaged if I just try the cabinet with my amp, for a short while? If not, can I use the sound to tell the impedance?
     
  9. You can buy a cheap ($20 ? ) multimeter to measure the resistance of the cab. If it measures 6-7 ohms, then it's 8, if you measure about 3 ohms, then it's 4.

    Set the meter for resistance. Plug a cable into the cabinet, and touch the meter leads to the tip and shaft of the 1/4" plug. Read what you got.

    If you go ahead and get a meter and learn how to use it, you'll be glad you did. It's useful.

    Chris