Originally Posted by
Simon Barden
The two outputs on the B2 are simply wired in parallel and it's just the speaker cabs connected to it that determine the overall ohmage and output power you'll get from the amp. Not the number of power outputs used.
The Ampeg fridge would appear to be 4 ohms (from web browsing), so the B2 can power that on its own, but if you add another cab, the overall resistance will drop further and you would be in danger of burning out the map or causing any overload protection in it to operate.
Parallel resistances are worked out using the formula (1/R1 +1/R2 +1/R3 etc.. = 1/Rtotal )
So with a 4 ohm (Ampeg Fridge) and 16 ohm (8T cab) load, you'd get 1/4 +1/16 = 1/Rtotal .
Expanding 1/4 to 4/16 to be the same units as 1/16, we get 5/16 = 1/Rtotal .
So our resistance is the inverse of that e.g. 16/5, which gives 3.2 ohms, so less than the minimum 4 ohms.
If the fridge is 8 ohms, then the overall impedance would be 16/3 = 5.3 ohms, which would be fine. If it is the stereo 4 ohm fridge cab then by putting it into stereo mode, you could have half of it powered at 8 ohms, and also power the 8T as well from the B2. It means half the fridge won't be used, but that's the compromise you'll have to make if you want to use the 8T and fridge together without using another amp. I suggest you try it and see what it sounds like. - but make sure the fridge is in stereo mode, not mono, and that only one side is being powered.
On the B2, you can attach one cabinet of 4, 8 or 16 ohms on its own, or two 8 ohm cabs or a 16 ohm plus a 5.3 ohm cab. If the cabs had their own parallel outputs, then you could attach four x 16 ohm cabs (for a 4 ohm resultant load).
To properly drive the fridge and the the 8T together, you'd need an amp that was happy driving down to 2 ohms, or another power amp to drive either the fridge or the 8T. But you can use the power amp section in one of the other amps - like the B1, to do this - especially as its already in the same rack case.
Reply With Quote
