ohms question again

[tacklebox455]

i have a sunn head that has 16,8,4,2 ohms select,
  i have a speaker cab that is 16,8,4 ohm mono.
 is it better to run amp head at 4ohm 8 ohm or 16 ohm?
if i remember right the less ohms you run the better, someone please correct me if i'm wrong and could you explain the benefits of which is better.

thanks

[EdBass]

I assume you are referring to a tube head since it has selectable output impedance. If so, the important thing (and the reason that you have multiple choices) is to match the amps impedance to the cab.
The amp doesn't care which output transformer tap you are using, it only cares about the load. The output transformers function is to match the amps output impedance with whatever speaker load you are using, and the reason that they often have selectable options (the 16,8,4,2 you mention) is to provide speaker configuration options.

With transistor amps the lower the load impedance the more power the amp will produce, at least up to the moment it self destructs anyway.

Also, what mono cabinet has 16, 4, or 8 ohm options? 

[Isaac]

My guess is that it's 16 or 4 mono, 2x8 stereo.

[tacklebox455]

Issac got it right its a 16/4 ohm mono 8 ohm stereo cab.

so i take it that running at 4ohms wont make the trannys run any cooler or any hotter?

i had always heard that running 4ohms would give tubes more life than running say 16 ohms

[EdBass]

so i take it that running at 4ohms wont make the trannys run any cooler or any hotter?

There is usually a slight performance variation between the taps, which can be accentuated by the fact that the loads we are describing are nominal impedance rather than a fixed resistance, but I doubt there would be a measurable difference in transformer temperatures; provided that you are using the output transformer to match the load with the output stage of the amp as it was designed to do.

i had always heard that running 4ohms would give tubes more life than running say 16 ohms

Nope, as I posted earlier the amp doesn't care which impedance setting you choose; provided your setting is the same as the speaker load you have it plugged in to.
The function of the output transformer in your 2, 4, 8, 16 ohm selectable output amp is to make a 2 ohm, a 4 ohm, an 8 ohm, or a 16 ohm impedance cabinet look exactly the SAME to the output tubes.

[tacklebox455]

ok just wanted to clear that up i have always known you have to match the amp to the cab ohms so this answers all my questions thanks guys