Boundary Mics vs Overhead Mics for acoustically challenged meeting room

D

Daniel Postilnik

Junior
Jan 14, 2011
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San Francisco, CA
Hi folks,

I'm responsible for the AV system in a meeting room that has high concrete ceilings, 2 bare walls, and a long glass facade. The original system was spec'd with two Clearone hanging array mics about 5 feet above the table - each is a little capsule with 3 mic elements that are processed by a Clearone processor. I trust that the processor is doing its job - we have one running with table mics in a different room and it's great - but the audio quality on conference calls is abysmal, probably because the mics are picking up mostly reflections.

I saw that Shure put out a wireless boundary mic (http://www.shure.com/americas/produ...systems/ulxd6-boundary-microphone-transmitter) that seems to compete with the Revolabs systems, but much cheaper.

The conference room has two ~6 ft tables abutting against each other for roughly 12 ft total length, and there is about 4 feet on each side of the table until the wall.

How many mics would be appropriate to cover people seated at the table? I would probably choose the cardioid option to minimize reflections in the signal. Our user base would not mind moving the mics around to bring them closer to a speaker if needed. Would 4 cut it? Will I likely get better results than the ceiling mics?

Thanks in advance for help!
 
To reduce the amount of reverberent sound on the conference call audio, you need the distance between the microphones and the talkers to be less than the critical distance for the room.

Given that the current microphones are ~5' from the talkers (assuming 3' vertically and 4' horizontally), you'll need to get the microphones closer than that to the talkers. With tabletop microphones, you're down to ~18" vertically, and with 4 microphones on a 12' table, you're down to ~30" horizontally, for a total microphone to talker distance of around 3', so certainly an improvement. Will it be enough? Hard to say without acoustical measurements of the room.
 
Rob Timmerman said:
To reduce the amount of reverberent sound on the conference call audio, you need the distance between the microphones and the talkers to be less than the critical distance for the room.

Given that the current microphones are ~5' from the talkers (assuming 3' vertically and 4' horizontally), you'll need to get the microphones closer than that to the talkers. With tabletop microphones, you're down to ~18" vertically, and with 4 microphones on a 12' table, you're down to ~30" horizontally, for a total microphone to talker distance of around 3', so certainly an improvement. Will it be enough? Hard to say without acoustical measurements of the room.
Click to expand...

Ok, this is reassuring. Getting the mics closer will help. Given that they are floating mics and can be moved closer to the speaker as needed, the distance will likely often be less than the 30" you figured. Thanks for doing those calculations!
 
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