I've started stereo-miking my guitar amp, which sounds great when both rhythm tracks are panned wide apart. However, I'm unsure how to pan those mics for a guitar solo. Do you advise panning stereo guitar solos close to the centre to enhance definition, or would you ever pan them wider apart?
SOS contributor Mike Senior replies: It's not clear whether by 'stereo miking' you mean a traditional crossed/spaced pair of matched mics, or two mics with different characteristics that have been combined for a fuller tone (something I normally refer to as 'multi-miking'). With a traditional stereo setup, panning the mics will likely give a fairly balanced stereo image, whereas with a multi-miking setup panning the mics may spread the instrument's spectral content more haphazardly between the speakers, depending on the frequency response characteristics of each mic. So, if you've used a multi–miking approach and a stable stereo image is important to your guitar solo, then perhaps keep the microphones panned fairly close to the centre of the panorama.
Some of the worst mono-compatibility problems I tend to encounter with SOS reader mixes arise when guitar multi-mics have been hard-panned without anyone ever checking whether they're phase-cancelling horribly when summed.
If you're using a more traditional stereo mic array, or don't mind the image instability of opposition-panned multi–mics, then the extent to which you opposition-pan the two mics will affect the solo's mono compatibility. If the solo guitar carries the main melodic content when it's playing, then that would be an argument for keeping the mics panned fairly central, and then perhaps using a widened delay or reverb effect to cover more of the stereo panorama if necessary. (That way, in mono only the guitar's effects level will suffer, not its direct sound.) However, lead guitar lines often perform more of a counter-melodic function, filling in behind and between lead-vocal phrases, and in that case you might actually prefer to pan the guitar mics fairly wide apart, firstly to provide better separation between the parts in stereo, and secondly to reduce the likelihood that the guitar line distracts from the vocal under mono listening conditions, where vocal intelligibility often becomes a higher priority.
There is one other consideration to bear in mind when opposition-panning any dual-miked guitar cabinet, and that is the phase relationship between the mics, because if the mics aren't perfectly phase-matched then you'll get more comb filtering between them in mono than in stereo. Indeed, some of the worst mono-compatibility problems I tend to encounter with SOS reader mixes arise when guitar multi-mics have been hard-panned without anyone ever checking whether they're phase-cancelling horribly when the left and right channels are summed. So if you do choose to opposition-pan your guitar solo's mic signals, make sure you've phase-matched them as best you can first — there's more advice on how to do this in my 'Phase Demystified' article from SOS April 2008 (https://sosm.ag/phase-demystified).