How far can I mike a conference with the PZM-10?

The FAQs say the maximum distance mouth-to-mic for the PZM-10 is 3 feet. I need better than that because I am unable to sway folks from using ceiling mics. We would be using the be using Vortex 2280 or 2241s for DSP to reduce audible reverberation. In that case, what is the effective maximum distance for the PZM-10 and separation distance? With the PZM-10 and Vortex, does the 3:1 still apply for phase cancellation?

Reply: Any time a person sits between two mics that are on, the 3:1 rule is violated, so some comb filtering is inevitable. Sorry, I have no experience with how the Vortex affects the 3:1 rule.

The spacing between microphones should be 2X the distance from microphone to mouth. This results in even coverage of all the people (approximately equal loudness). So in a room with an 8' ceiling, if the mics are mounted in the ceiling, they are about 4 feet from the participants' mouths. So the mics should be 8 feet apart.

The Signal-to-Noise Ratio of the PZM-10 is 68 dB at 94 dB SPL, 48 dB at 74 dB SPL (conversation at 1 foot), and 36 dB at 62 dB SPL (conversation at 4 feet). The noise referred to is the mic's electronic noise in a room with no acoustic background noise. If 36 dB S/N is acceptable, then the 4-foot miking distance (of mics on an 8-foot high ceiling) should work.

That figure is for a mic directly above a person speaking. People between two mics will be a little farther away, so the S/N will be a little poorer.

If 30 dB S/N is acceptable, then an 8-foot miking distance should work. We're assuming that the Vortex is eliminating most of the audible room reverberation.

If the ceiling is very high, you could hang some 2 ft x 2 ft clear plexiglass panels 4 feet over the table and mount PZMs in them.