I asked a local soundman friend for input, and here is his response (when he mentions the 10th string, he is talking about Pedal Steel... we both play Steel).
'Question for ya...
If I am running a 1x12 cab with a JBL, I don't think polarity matters when hooking up the JBL, although I prefer the speaker to move outward when I play, so I hook up the pos/neg leads that way.
Here's the question...
If I am mic'ing the 1x12 cab, does polarity matter for any reason?
Does it matter if my speaker moves forward, and maybe other speakers on stage move backward and/or forward (rhythm, lead, bass, keys, steel)???
That’s a muddy can of worms, Pete, but I will endeavor to bring some clarity to the waters…
Interestingly enough, JBL’s polarity is opposite that of most other manufacturers, also different amps present different output polarity relative to the input, so simply hooking positive to red does not always guarantee phase coherency.
In regards to your first comment, hook up the speaker and set it where you can see the cone clearly. Damp the strings with your left hand and with your right thumb strike the 10th string hard in the normal fashion, i.e. pushing the string away from you, watching the speaker cone to see which way it travels when you do so. Try this several times to be certain that what you are seeing is consistent. If the cone moves forward (outward) you are in phase, if it retracts when you hit the string switch the wires and try it again. Being as anal as I generally am I personally might make a note about the final hookup on a piece of tape and stick it inside the amp for future reference, remembering that if you change speakers you will have to re-check the phase response.
Now for your real question(s):
Due to the time delay inherent in the amp and PA speakers not being physically aligned in relation to the listeners, combined with the fact that not all microphones, mixers, processors, amps or PA speakers maintain phase correctly, when mic’ing the amp it is a crapshoot. If the console has a phase switch or you have a phase-reversing XLR adapter you can try both ways to see which presents better low frequency reproduction, but remember that this perceived frequency response is also a function of where you are listening from, sound traveling through space in time and all. For this reason many – but not all – pro stage monitor systems are operated at reverse phase relative to the main speaker system. Certainly changing the phase of a mic relative to the speakers it is reproduced in will affect frequency response to a noticeable degree. Neither is scientifically “correct” so one can only pick one and stick with it.
As far as your amp speaker’s polarity relative to the speakers of other players it means nothing at all, as unless identical waveforms are being reproduced it’s all just sound in space; a reverse phase condition between two dissimilar waveforms is pretty much the same as if they were both IN phase and one was simply delayed a few milliseconds, which with different players onstage is going to randomly happen all night anyway.
However, if you were using two amps yourself it would matter a great deal as reverse phase speakers will generate comb filters from hell and that’s what it will feel like until you sort it out.
Keep me posted on your further adventures.
I think this is pretty much in line with what everyone is saying here.... right down to the OCD!
The nice thing about the MC250 (and the like), is that it is really easy to swap leads at the amp itself.
btw... Congrats on the MC250!
Here is a link to the Manual: