If you are attempting to mic a rotating Leslie, I agree with Joe about opting for mic placment at 90 degrees, as opposed to 180 (for the horns). However, per the below quote......." The horns are already 180 apart, so you'll want to have your mics at 90 degrees to get the true L/R auto-pan sound most folks want.
This is pure B.S...although the Leslie has 2 horns, only 1 is functional as the other serves as counter balance and does not produce sound. I use 1 U87 (or other large diaphragm condenser like AKG 414 if U87 is not available) on the front louvers and 1 on the side louvers for the horn (for a stereo pair). Since only 1 horn is functional, you are still getting the full doppler effect, regardless if you place mics at 90 or 180 degrees. I prefer 90 degree placement @ the horns because I also go stereo on the bottom bass with 2 Shure SM-7's (or Senn. 421's as an alternative) with 1 SM7 placed @ the front bottom bass louver and 1 @ the opposite side (90 degrees) from the top louver. I find the louvers to be a good selection for mic placement as they help deflect air from the speakers. Some engineers mic the open area on the rear of the cabinet, but the motor for the speed control tends to be noisy and is often audible when when the rear of the cabinet is miced. I have had good results with a hard pan for the horns and 10 & 2 pan on the bottom bass. A little leakage is not a bad thing and tends to liven the sound a bit. The best advice I can provide is to experiment with the room, mic placement and mic selection and go with what sounds best. The SM57 is a good alternative to SM7 on the bass, but I prefer a larger diaphragm if possible, like the SM7 or Senn. 421.
On another note, per the below article..."Believe it or not, a pair of the classic SM57's will usually sound great on the top rotors, and your choice of mic (usually an LD condenser for me) on the bottom, (with a little low-end rolloff?) usually does a great job on the bottom. If the band has a bass player, you may not be needing too much from the low end anyway (unless the organist plays PEDALS, too! Yeah.... ;-)
Again, this is B.S...The horn is producing hi-mid and hi frequencies. Stick with a condenser, preferably a large diaphragm when micing the horns. Vice versa for the bass. It would be counterintuitive to mic a condenser for low and dynamic for hi frequencies, this just doesn't make any sense.
Most of them are the wooden model anyway, with a 12 or 15 in the bottom, and a dual rotating horn (over a single tweeter/driver) up top. Depending on how well they've been kept up, they may or may not have the original wooden covers over the back areas. (Most leslies are used flipped around, with the nice "Furniture" side facing away, with the spinning horns exposed and visible from the audience persepctive.)
There's been a lot written over the years, and I recall Keyboard Magazine did a GREAT issue on this very topic a while back (late 90s?). (I don't get KYBD anymore, but I think they may have their entire past issue collection available online, or at least have articles available in a searchable database. Worth a few moments on their website, to be sure.)
Remember the whole organ leslie combo is a very dynamic, motion-based system, and it really lets the organ breathe, in a way. (There are some older (non-Leslie brand) Hammond cabinets that do NOT spin or move at all, and some older systems used a combination of these two. Hence the many sounds out there available on any given Jazz B3 combo recording.) On a loud rock gig, you may want to isolate it in a road case to get the most out of it. (Again, Keyboard magazine had a whole section on this, including Keith Emerson's custom, foam-lined road case that housed his Leslie 147 with built in mics, cables, etc.)
If you've got the Leslie isolated in a good sounding room, you can play around a LOT with close and distant mic'ing. Or, you can just get in close and work with tight mics and add your reverb and room tone later. You can even take some straight Organ alone (DI'd) and blend the mix to taste.
I prefer the 90 degree mic approach on the top. (Don't make the mistake of putting a mic wide (hard L and R) on each side, that's actually 180 degrees, and it will substantially negate any of the wonderul L-R panning & dopler effect you'll get with the horns moving. The horns are already 180 apart, so you'll want to have your mics at 90 degrees to get the true L/R auto-pan sound most folks want.
I don't have any pictures to show you (Maybe Keyboard mag still does?), but you can easily start with one mic slightly to the right of front/center, and the other one 90degrees to the left, even peaking inside the 4" top opening a bit. (don't get too close, or you'll get a lot of air hitting the mic as well...unless you WANT that effect.) You can also do this OUTSIDE of the entire wooden case itself, but you may be forced to do this on the covered, louvered side. (Which isn't all that bad either, and some would argue is a big part of the sound anyway......)
For the bottom rotor, a single mic (mono) is usually considered enough.
Most of this is low end material anyway, but the spinning drum does help move the sound around a bit. Don't get too close with that one, either..more than air hitting the mic, the big rotor at the bottom can really do some damage (Whack!) if it hits anything while spinning at the high setting.
Believe it or not, a pair of the classic SM57's will usually sound great on the top rotors, and your choice of mic (usually an LD condenser for me) on the bottom, (with a little low-end rolloff?) usually does a great job on the bottom. If the band has a bass player, you may not be needing too much from the low end anyway (unless the organist plays PEDALS, too! Yeah.... ;-)
I keep mentioning the Keyboard mag stuff, because they honestly DID cover this to perfection in their story (I think this was back in the 90's now...can't recall the year.)
And while there are tons and tons of great Jimmy Smith (and others') Jazz and Rock recording out there, I can point you to perhaps (IMHO) the best example of what a good, stereo-mic'd B3(or C3) should sound like in a recording.
Pick up a copy of Emerson, Lake and Palmer's "Brain Salad Surgery" and listen to the very first track with headphones on: The organ opening/intro to "Karn Evil 9, 1st Impression, Part 1". It's essentially a mini-2-part invention (like Bach) but done on a snarly, growly B3 just before the tune really kicks in. As good as it gets, IMHO. (Ditto for most of the rest of that record, but that's another story, another time...)[/QUOTE]