You DO NOT want a standard
PZM*, which is
omnidirectional. You want a
cardioid boundary
microphone, the most common of which is
Crown's PCC-160 (
PCC=
Phase Coherent
Cardioid), although there are others out there. Some guys prefer to use a standard appropriately sensitive small
condenser, and then mount it at the floor to get a boundary
effect that gives you the same end result as a
PCC, but with a (depending on the mic) better sound.
The PCC-160, while not the best
boundary mic out there, is the most common, and is pretty good for most jobs. It could work for this gig, but...
The KEY with boundary mics is to not think that you can just leave all of them up and let people talk. If you do that, you'll end up with all sorts of
phase cancellation. They need to be actively mixed, just as wireless mics would. The engineer needs to follow the action onstage and ride the faders to match which mics are nearest the action. Ideally, you want no more than one mic at a time up, but it can vary depending on the action onstage. In all honesty, mixing floor mics well is harder than mixing wireless, IMHO.
For your application, they could work, but they won't sound like close mics can, since they're more suited to subtle reinforcement (which, if you were using lavs, would be the ideal goal, too, although lavs can do that loud close mic sound, too, of course).
On a typical
proscenium stage, I recommend going for an odd number, typically 3 or 5 depending on the width of the
stage and the
blocking. Why an odd number? Because this tends to align with where much
blocking happens more often than an even number would...lots of action is usually blocked at center and at odd
spacing centers, just because things usually look more balanced this way. By having mics on those centers, you're more likely to be directly on-axis of a mic instead of split between two.
Best of luck,
Andy
*-Which, btw, is a specific brand name for
Crown's version of an
omnidirectional boundary
microphone (so called because it takes advantage of the boundary, or "pressure zone",
effect, which is what happens when a
microphone is placed directly on a reflective surface, and the
reflection of the sound hits the
microphone perfectly in
phase and at the same
level as the direct sound, resulting in a doubling of
level at the
microphone)