View Full Version : Cardioid Mic for Conference Table Recording?
October 25th, 2007, 01:18 PM
My work is videotaping meetings, and my problem is getting better sound quality from those participants at the far end of the table who promise they'll probably not have anything to say, except for those occasions when they do.
I have only so many mixer slots, so I get to dedicate one to that crowd. I can't hang a boom or move people around the room. However, I don't have to record their voices in perfect musical quality, and a certain amount of room noise is okay. Their questions and answers just have to be clear. I have used a piezo flat mic on the table, but it gets too much noise, so I'm looking to get a mic on a short stand. I originally looked for an omni, but I can't find one for near the cost I'd like to spend.
Can a unidirectional condenser mic, such as a Shure SM58, be pressed into adequate service for this task? Or would this be too directional for anyone more than a couple feet apart? Would I capture only the person at whom the mic is most directed, with diminishing returns for others seated down the row?
If you can picture a 12ft long conference table, with a mic on a table stand in the middle, pointing towards one end, then thats what my situation usually would be. It seems to me that the directional quality will hep boost the guy at the end, with the others being closer to the mic and therefore clearer. Plus a unidirectional/cardiod might help keep out noise from the ceiling area.
Am I off-base?
October 25th, 2007, 01:42 PM
First, I think it's just a typo, but the SM58 isn't a condenser mic.
Second, you say you have only one mixer input to dedicate to that end of the table. You didn't say just what your budget is, but an inexpensive (sub $300) wireless kit with an omni lav mic could be put to use here. You could hide the lav almost anywhere to keep it out of the shot, and still get the benefits of an omni pick-up pattern. (For those that will suggest a wired mic is the best way to go, I agree. I'm just offering another option.)
Also, did you try using your piezo flat mic on a small piece of foam to isolate the table noise somewhat?
October 25th, 2007, 01:57 PM
I'm researching as I post.
Yes, that is well beyond my budget, and in fact I have a lav for every pot on my mixer (four), but laying the lav on the table is less than perfect. Too much noise, especially from paper shuffling. I am thinking about making a little stand for the lav, but I also thought that a handheld omni (or cardioid) would be better.
Let's say I have to get a handheld. Would the cardioid work?
October 25th, 2007, 05:29 PM
there are special mic for this purpose (you see them on conference phone or video conference equipment). they are flat and goes directly on the table.
they use the table surface to improve sound capture.
2 of them should be ok to cover the table described (one on each channel).
October 25th, 2007, 08:19 PM
I have seen tabletop mic's in action (have not used them personally,, was on the business end, being recorded). Fr reference in looking them up, here are some models that have been mentioned to me - Audio Technica models - U841A & U 891R, Shure MX 393 and AKG C-680BL. I have no experience with them personally, just am aware that this type of recording has been used successfully in Board Meetings, etc that I have been involved in. Hope that helps.
October 26th, 2007, 10:04 AM
You say that you already have a PCM mic? use that, (perhaps with a small piece of cloth or foam underneath it to minimize table rumble) but the mics that will work the best are expensive, and in high end video conference are processed by a DSP unit (Audia or Clear one) to reduce echo and feedback. as well as acting as an auto-mixer with auto level capabilities. have you considered cliping your wireless lav to the ceiling grid and letting the mic hang just out of frame?
October 26th, 2007, 11:14 AM
...have you considered cliping your wireless lav to the ceiling grid and letting the mic hang just out of frame?
I like that idea.
October 27th, 2007, 03:28 PM
The noisiest things on the table are people rustling papers about and stuff like that. In fact, sometimes their binders of paper are obstruction to the flat table mic. Flat table mics are only useful in a perfectly motionless group, otherwise they're bad. So thats why I'm looking for a mic I can put on a stick about a foot off the table.
I'll try the foam padding, though. That might help. Thats a nice cheap thing I can afford.
And no, no wireless lav, and no ceiling grid. This is real-world. I walk into conference rooms, I'm lucky to get a corner to sit in, and I have to setup in half an hour, breakdown same. So you see I'm very certain that I want a hand-held type mic on a stand. Any comments as to the question I asked about whether a cardioid mic would work better than an omni in such a situation would be great.
October 27th, 2007, 04:49 PM
Well some times the challenges cannot be overcome without some sacrifices. I make a living designing and implementing video conference rooms for a big financial institution . your idea of a cardioid facing the far end of the table will add to the level of people sitting closest to the mic, however be prepared for some serious phase issues (big hollow sound). this can be shifted in post, but only if you record this mic on a discrete track, then you can adjust phase in a program that will let you time shift this mics signal to time align perfectly with the cameras track. also keep in mind that if the table is busy enough to cover up a table mic, then its probably busy enough to require a fairly sturdy mic stand as well (so as it not get bumped over). just some of the things to look out for. keep in mind that multi mic setups in video conference rooms are aided by DSP processors that handle the echo and phasing issues, but again this can be overcome in post with proper technique. the reason multi lav set ups work is because their gain is just enough to pick up the subjects and not the room, same goes for shotguns. but in a situation where you need to pick up the room then phase will be a great contributor with multi mic setup regardless of pattern, as the sound from the speaker will arrive to both mics at diffrent times, as well as the reflections of the room will hit the mics at diffrent times as well.
October 29th, 2007, 09:20 AM
Give us some additional information about the rest of your setup. What other mics are you currently using, how many mixer channels are you using, how many recording channels do these get mixed down to, and is there someone dedicated to actively mixing these mixer inputs during the recording?
As to your original question, I like the AT3031 cardioid or AT3032 omni for these situations. They are $169 or less at a number of sources. They have very low self-noise and good sensitivity. They run on 11 to 52 volts of phantom power and have a bass roll-off at 80Hz.
They sound reasonably good off-axis, but as already mentioned, if you're mixing down multiple sensitive mics at multiple locations in the room to one recording channel, you will have phasing issues unless they are being actively controlled by a human or an automixer.
October 29th, 2007, 01:47 PM
I've had great success recording large groups at conference tables using these inexpensive condensor mics from Samson. Just make sure you put them on a foam pad to help reduce table noise. ( thick mouse-pads would probably do the trick )
Samson CM11B Omnidirectional Boundary Microphone
October 29th, 2007, 03:24 PM
I too have one of those inexpensive Samson boundary mics. It's been used by many many people and all were very happy with the results. Obviously not as good as having one mic per person each recording into its own track but for the money and ease of use they work very well.
They come in either omni or cardiod. For a longer table two cardiods might be a good solution.