Need schooling on Speaker load with All tube amp

Discussion in 'Amps and Cabs [BG]' started by 707GK, Dec 18, 2014.

  1. 707GK


    Jun 13, 2013
    I have a 4x10, 8ohm. I believe one speaker is bad. The manufacturer has recommended making sure this is the speaker making the unwanted noise by disconnecting & playing through the other 3 & listening to whether or not this gets rid of the unwanted noise. The manufacturer of this cabinet only makes amps with SS power sections that, more or less, automatically adjust to different loads. So this method seems reasonable, if I were using one of their heads.

    However, I currently in my possession only have 2 all-tube amps that both have 2, 4, & 8ohm speaker outputs. Removing 1 speaker should increase the resistance of the circuit, if I am understanding correctly.

    Will running the 8ohm output into an 8ohm cabinet with 1 disconnected speaker for a few minutes do any damage to my tube amps? According to the manufacturer, removing 1 speaker should increase the speaker load to around 10ohms.

    Thanks in advance.
  2. Bassmec


    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    The chances are your cab is wired in series parallel, so the impedance of each driver is 8 ohms.
    Because that's two pairs of speakers wired in series for 16 ohms each pair and those two pairs are then wired together in parallel. Thus divide by 2 and you are back to eight ohms.
    Just take each driver out of the cab and connect to your 8 ohm output.
    You will soon find the nasty buzzie one.:)
  3. 707GK


    Jun 13, 2013
    I am not so sure that is the case, on their website it shows replacement speakers being 32ohms each for the 8ohm cabinet.
  4. dincz


    Sep 25, 2010
    Czech Republic
    In that case, yes, just disconnect one at a time. Running the amp into 10~11 ohms instead of 8 ohms is not a serious mismatch.
    B-string and 707GK like this.
  5. 707GK


    Jun 13, 2013
    Ok, thank you
  6. beans-on-toast


    Aug 7, 2008
    As was mentioned, a short test is not going to harm the amp. Otherwise connect a radio or some other source and see if that will reveal the problem.
    707GK likes this.