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Question about heads/cabinet ohms

Discussion in 'Ask Doug Johns' started by bassbiker1, Mar 13, 2012.

  1. bassbiker1


    Mar 13, 2012
    Currently I have and am using an ampeg b2r head (not the newer b2re head). It's rated at 350 watts at 4 ohms and 200 watts at 8 ohms. I am using it plugged into one 4 x10 cabinet which is the ampeg b410hlf. That cabinet is rated at 400 watts at 4 ohms.

    First question. Am I currently running my head at 8 ohms or 4 ohms? Due to head/cabinet mismatch, is it a problem to continue running my set up this way?

    Second question. I want to add an 1x15 to my stack for larger venues. Can I add an 8 ohm ampeg 1x15 cabinet to my current setup without blowing things up? If not, assuming I want to keep my existing head and still run a 4x10 and a 1x15, do they need to both be 8 ohm cabinets?

  2. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    The head and cab are a perfect match. The cab is 4 ohms, and the amp works with a 4 ohm load. If you add an 8 ohm cab to the 4 ohm cab, the total load will be 2.67 ohms--and your amp will burn up trying to do that. If you want, you can use the 8 ohm cab by itself, that's not problem; or you can use two 8 ohm cabs, which will make a 4 ohm total load.

    You need to read a couple of things: first, the FAQ in the Amps forum. Second, there are several threads about combining a 4x10 with a 1x15; in fact I think one of those threads is on the first or second page of the amps forum right now. Oh yeah, and third: the FAQ in the Amps forum. ;)