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Ohm ratings, and running cabs in parallel setups...

Discussion in 'Amps and Cabs [BG]' started by Not Mark Westlake, Apr 11, 2004.


  1. Ahoy there,
    I'm a rig virgin having been a full-on combo boy before.
    I've got myself a head (Behringer) and cab (Ashdown) sorted, but I have a question - the Beh head has a speak-on output for a 4ohm cab, and then 1/4" jacks for a pair of 8ohm cabs to run into. I'm hoping to get a 1x15 to go with said 4x10, but for the time being can I run this 8ohm cab through one side of the pair of the 1/4" jack sockets? I realise it won't be as loud due to the high resistance, but it should work, yeah?

    Thanks for anything,

    Mark.
     
  2. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    As I understand it, the minimum impedance that the Behringer head can handle is 4 ohms. The speakon and 1/4 in. jacks are connected in parallel so any load you place on the amp counts. The amp doesn't care whether you use the Speakon or the 1/4 in. jacks.

    If your 4x10 is an 8 ohm cabinet (which I believe it is from what you've written), you can connect one more 8 ohm cabinet. At that point, the total load impedance that the amp sees is 4 ohms.

    By adding a 1x15 you'll gain more from the extra cone area then you will from the output power increase of the amp.

    I hope that this makes sense...

    Have fun!!!
     
  3. Tez

    Tez

    Jan 24, 2004
    Australia
    I have a Beringer 120 combo with the 12 " 4 ohm speaker I had to make a connecting box with 2 outs in Parrallel for it so I can run a 15" BW 4ohm and since it drops the ohms to 2 ,the amp produces more volume without any Ill effects . As I play behind a 26 piece Big Band I need to move more air without pushing the volume too much . maybe if I tried to use it in a loud rock band it might Sh*t its self but its been fine up to now. and no doupt the wierd tone settings I use does not overload the power amp Tez

    (Settings ,My Bass has no tone pot the amp Bass tone pot is on-4 Low mid full minus 6 mid full minus High minus 4 and shape control is on 4 ) I run a Ber valve pre amp to boost the input signal as my P Pickups are wired in Parrallel which cuts the output of the pickups to 25%)
     
  4. Hi there you two,
    Yeah, I get the deal with adding cabs - it's why I chose the 8ohm Ashdown so I could upgrade later. I was just kinda seeking reassurance I could hammer it into one of the 1/4" jack sockets with the other one being empty without it exploding and taking out my house or anything :)

    What DOES the shape do? I can kinda hear the difference when I stomp on the Shape pedal, and I can sort of see the difference when I turn it up, but how does it work and what does it do?

    Thanks,

    Mark.
     
  5. Tez

    Tez

    Jan 24, 2004
    Australia
    Shape function would most likely be a tone pot that is parrallel to the others that ,would be in series with each other so when you alter it the overall sound is affected on all frequencies mind you thats just a Guess and I will stand corrected by those who Know

    Tez
     
  6. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
  7. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    :eek: Yes, your tone settings are probably saving you but you are overloading the amp. You probably won't kill it, but you will greatly reduce its lifespan. I hope you have a backup..... :eek:
     
  8. Hey Billy,
    I read my manual here for my Beh but it doesn't really clear it up for me :S I still just don't fully get how it alters the sound, but then again, I'll get it sounding nice so it doesn't matter either way!
    Thanks anyway,
    Mark.