using 2 outs on amp to 1 speaker cabinet?

[ironlung40]

Hey all,

I've got a head that only runs 8 or 4 ohms. my speaker cabinet is a 16 ohm 4x12. If I use two speaker cables from 2 outputs on the amp and hook these into the 2 inputs on the cabinet will this make the amp see an 8 ohm cab?

[Gonzo]

I would read the cab jackplate to see what the two inputs are wired as if they are both engaged. I almost got into a bit of trouble recently with this. My 1960a cab is wired so that if both jacks are plugged in, it is an 8ohm load on each-if yours is this way, and you run two cables out of your amp in parallel to two 8ohm loads, the amp is getting a 4ohm total resistance. Check this link:

http://www.tunemybass.com/bass_amps/how ... inets.html

of course that is from a bass player, but ohms law is the same lol.

if both inputs on the cab are 16ohm, I would figure that the amp would get a 8ohm total resistance with both cables run out of it. If you're not sure, because they aren't marked or whatever, go to the celestion website and check out their speaker wiring diagrams and check it to yours:

http://professional.celestion.com/guita ... /index.asp#

If you are still unsure, do what I did and go to a hardware store and buy an inexpensive ohmeter ($25) and check what resistance is on the circuit. The ohms will not read exactly btw, usually slightly off, but you can tell the difference between 8 and 16. This is a cheap investment as compared to frying your precious output transformer.

I'm no expert, but hope that will help you..


Good luck!

[ironlung40]

thanks. Yeah the ohmeters don't read the same type of resistance that the 16ohms rating is specific too. I don't really know the difference, but there is one.

Your info is greatly appreciated.

It makes total sense. If the cab was a 16 ohm, and using 2 inputs isolated 2 sets of the speakers at 8 ohms, you could think of it as 2 separate cabinets running at 8 ohms. Then running your head into 2 separate 8 ohm cabs would yield a 4 ohm burden on the head. 1/T=1/a + 1/b. Where t = total impedance, a=impedance speaker a, b=impedance speaker b so 1/8 +1/8 = .125 +.125 = 0.250------->1/0.250=4 ohm
this assumes parallel wiring.

I just need to double check how my jack functions exactly.

thanks.