hey all, i have a hartke HA3500 and an avatar 4x10. the head puts out 350 watts into the 1200watt cab at 4 ohms. if i was to get an 8 ohm 115 cab what would the resulting impedence and power output be to each amp?
The resulting total impedance would be 2.67 ohms. The 4-ohm cabinet would get twice the power that the other one got (so it would get 2/3 of the total). However, it looks like the 3500 isn't rated at less than 4 ohms, so I wouldn't try it.
It's very important not to go below the minimum rated impedance for an amp. Since the Avatar is 4 ohms, my guess is that the speakers are 16 ohms all connected in parallel. You could rewire your Avatar for 16 ohms and then use it with the 8 ohm 15. The resulting impedance would be 5.3 ohms.