Microphone for recording a round table discussion

[Kathy Smith]

Originally Posted by Oren Arieli

Always separate the tracks when you record them. If an open mic starts picking up lots of noise and you're mixing it with the presenter, there is no way to separate them in post.
The boundary mics are a good start, you'll probably want to use at least two and record them to a portable mixer/recorder like the Zoom H6. Not much different at that point from using multiple Zoom H1's, as you'll have work to do in post to pick the best audio track. Leaving them all open means you pick up random noises in addition to the signal that you want to keep.

If you're dealing with 2 tracks on your camera, devote one to the presentation, the 2nd one to one of the boundary microphones, and you can use a zoom on the opposite site of the room (mixing in post as needed). Adding 2 more Zoom H1's is still cheaper than adding 1 boundary microphone.

I did this exact same thing just last week, and the Zoom had better signal than the boundary mic (which still picks up much of the table noise/thumping, etc.). I would recommend a bit of rubber padding like a mouse-pad under any boundary mic, which will help to isolate those thumps.

I have one H4N zoom recorder, but 1 won't help me, I would need two, right? Where do you put the zoom, just lay it on the table? Are you saying the the internal zoom mics are better than the boundary mics? SO ultimately, would I be better off having two zoom recorders on the opposite sides of the table instead of two boundary mics on the opposite sides of the table?

[Greg Miller]

I'm a little puzzled here, in that you haven't even told us the rough dimensions of the table (is it round, square, a long rectangle, etc.?), nor have you told us whether the presenter will be seated at the table or somewhere else in the room.

Let's assume the presenter is NOT seated at the table. Then mic his lav on a separate channel, all by itself.

I think boundary mics are a good choice for this, so if you're going to buy a pair, do not mix them together; record them separately on the two channels of your Zoom.

In post, obviously, first sync everything together. Take only the presenter mic when the presenter is speaking. When someone at the table is speaking, pick whichever boundary mic has better audio, and use only that one mic. Do not ever mix the two boundary mics together, or you may have phasing issues between the two of them (as well as additional noise and reflections from the room).

You could probably find some less expensive boundary mics if you're pinching pennies, but those Shures are certainly decent mics.

[Kathy Smith]

Originally Posted by Greg Miller

I'm a little puzzled here, in that you haven't even told us the rough dimensions of the table (is it round, square, a long rectangle, etc.?), nor have you told us whether the presenter will be seated at the table or somewhere else in the room.

Let's assume the presenter is NOT seated at the table. Then mic his lav on a separate channel, all by itself.

I think boundary mics are a good choice for this, so if you're going to buy a pair, do not mix them together; record them separately on the two channels of your Zoom.

In post, obviously, first sync everything together. Take only the presenter mic when the presenter is speaking. When someone at the table is speaking, pick whichever boundary mic has better audio, and use only that one mic. Do not ever mix the two boundary mics together, or you may have phasing issues between the two of them (as well as additional noise and reflections from the room).

You could probably find some less expensive boundary mics if you're pinching pennies, but those Shures are certainly decent mics.

Sorry, the table will be rectangular (I don't know the size). The presenter will be at the table but I'm guessing standing up. I don't know for sure, though. One of the shorter sides should be available for my camera, so the people would really just occupy 3 sides of the table, the two long ones and one short side.
I wasn't going to mic the two boundary mics together. I was planning on recording all mics on separate channels. Since I have two channels on the camera, I thought I would record the two boundary mics to the camera and the main speaker could be recorded to the H4N. Originally I was just going to have 2 mics but I since I have a Zoom recorder I thought of utilizing it to gain an extra channel.

[Jay Massengill]

What model of cameras will you be using so we'll know their audio capabilities?

Will you have access to a mixer, especially one that has multiple outputs so that both cameras and the "extra" channel of the H4n can have clean, strong audio to aid in synchronization on the timeline and simply benefiting you during logging, cutting, checking lip sync when you cut down to smaller bits of video etc.

For example, even a small mixer like a Mackie 1202-VLZ or equivalent would allow the appropriate mics to be preamped cleanly and sent separately during either the presentation or the discussion to both channels of both cameras as well as separately to the H4n.

In other words, having weak onboard audio on one of the cameras and lavalier-only audio with very weak pickup of the group on the H4n will increase the burden of logging, initial sync, editing decisions, lip-sync in closeups if you have drift, etc.

If I was doing this project, I would use a mixer, the two boundary mics, the presenter's lavalier, and a separate clean cardioid overhead mic (ME64 or AT4021) as a backup.

For the presentation portion, the lavalier would be sent to both cameras and the H4n. The backup overhead mic would go to the second channel of the H4n.

For the group discussion segment, the two boundary mics would each be fed separately to both cameras. The lavalier and the backup cardioid over the group would be sent on separate channels to the H4n.

The goal is to always have a clean strong signal from the mic that's most helpful to syncing your camera shot, even if it's only used as a guide. Having extremely weak guide audio is a royal pain.

[Roger Gunkel]

Just to reinforce the value of boundary mics in the situation you are talking about, a Zoom H1 instead of a boundary mic will not be sufficient. The point of a boundary mic is that it will considerably reduce pickup of room reflections because ot the way that it picks up the sound waves. Room reflection of the sound being recorded is the problem in this type of recording. Have a quick read up on the way they work and you will see why. Certainly use a lav on the speaker, as his presentation will be the one that needs the clearest sound, but don't expect too much from a suspended overhead mic, as this will again pick up all the reflected sound within the room, although always useful as an emergency backup.

I agree with Greg that there are a number of considerably cheaper alternatives to the Shures and for many years I used the Tandy/Realistic PZMmics which were incredibly cheap but gave great results, but probably no longer available.

Roger

[Roger Gunkel]

The Audio Technica Pro44 boundary mic should give similar results to the Shure and they receive good reviews at a much lower cost than the Shure. Here's a link to it at B&H https://www.bhphotovideo.com/c/produ...2C113041916107

Roger

[Dave Farrants]

Agree with Roger, the Realistic PZM's are legendary for round table work, I've used them many times, there are 2 on eBay in the States for around $50 BIN.

[Kathy Smith]

At this point, I'm not concerned about the cost. The Shure's are coming tomorrow. I will be recording to Canon XF305 and lav will be recorded to Zoom H4N. I will not be using a mixer. The second camera is not going to be stationary. I will not be recording clean sound to it, just whatever the internal mic will pick up for syncing purposes.

[Jay Massengill]

The XF305's have pretty good audio circuits.

The Shure boundary layer mics have very good specs for high signal to noise ratio, but I have only used Crown and Audio-Technica models. I still have my two original Radio Shack PZM's as well.

Based on the specs, the Shure's should be a good choice.

Can you use a clapper for a sync mark at the start and at the end of the recording? That will help if not sending full volume guide audio to all devices, as well as giving a better idea of how much drift you're having with the H4n compared to the cameras.

Also put as much effort as possible into softening the room with whatever material or padded furniture is available.

Good Luck!

[Kathy Smith]

Originally Posted by Jay Massengill

The XF305's have pretty good audio circuits.

The Shure boundary layer mics have very good specs for high signal to noise ratio, but I have only used Crown and Audio-Technica models. I still have my two original Radio Shack PZM's as well.

Based on the specs, the Shure's should be a good choice.

Can you use a clapper for a sync mark at the start and at the end of the recording? That will help if not sending full volume guide audio to all devices, as well as giving a better idea of how much drift you're having with the H4n compared to the cameras.

Also put as much effort as possible into softening the room with whatever material or padded furniture is available.

Good Luck!

I only have one sound blanket. I'm not sure how much it will help me. I need to put it somewhere where it doesn't show in the shot. Can I put it under the table?

[Greg Miller]

Under the table is probably the least effective place. You want to put it where the sound waves will hit it, and where it will cover a reflective [hard] surface. Under the table, you already have legs and laps, some (or all) of which are wearing pants, chair seats (hopefully upholstered) and, hopefully, carpet. The sound waves will first have to bounce off a wall to get down there in the first place, so that's a pretty useless location.

Just pray that nobody is farther than arm's length from the nearest mic, and that the room is pretty big and diffuse, and with absorptive tiles on the ceiling ... at the very least.

Another concern nobody has mentioned is noise from mechanical systems (HVAC, etc.). Boundary mics will *not* help with that; they *will* pick up that noise clearly. The only thing that helps with mechanical noise is minimizing the mic-to-mouth distance so you can run your gain as low as possible.

Believe me ... I just spent a few hours cleaning up an 8-minute clip recorded in a live room with unbelievably high levels of LF noise from air handlers and cooling equipment. The mic was positioned about three feet from the talent, or so I am told. I was not permitted in the room because of some poorly-defined "intimacy" issues. (But I was allowed to hear the recording later ... go figure!!!)

[Graham Bernard]

I've been using this Audio Technica Boundary mic for many years : ATR97 Omnidirectional Condenser Boundary Microphone (DISCONTINUED) || Audio-Technica US

Although it is discontinued, AT do have upgrades. I use it attached to a SenniTX hidden either in a bowl or gaffered under the table! I've used it for Round table and focus groups where I can trundle my XF300 around the "discussions". Combining its output with the on-camera mounted shottie supplies an urgent and "real" sound design. It's as if the viewer is in the room listening to the group.

It's given me great service and the output quality is way above its cost!

Grazie

[Roger Gunkel]

Hi Kathy,

It would be great if you could come back on this to let us know how you get on with the Shures and the overall quality you managed to achieve.

Roger

[Kathy Smith]

Originally Posted by Greg Miller

Under the table is probably the least effective place. You want to put it where the sound waves will hit it, and where it will cover a reflective [hard] surface. Under the table, you already have legs and laps, some (or all) of which are wearing pants, chair seats (hopefully upholstered) and, hopefully, carpet. The sound waves will first have to bounce off a wall to get down there in the first place, so that's a pretty useless location.

Just pray that nobody is farther than arm's length from the nearest mic, and that the room is pretty big and diffuse, and with absorptive tiles on the ceiling ... at the very least.

Another concern nobody has mentioned is noise from mechanical systems (HVAC, etc.). Boundary mics will *not* help with that; they *will* pick up that noise clearly. The only thing that helps with mechanical noise is minimizing the mic-to-mouth distance so you can run your gain as low as possible.

Believe me ... I just spent a few hours cleaning up an 8-minute clip recorded in a live room with unbelievably high levels of LF noise from air handlers and cooling equipment. The mic was positioned about three feet from the talent, or so I am told. I was not permitted in the room because of some poorly-defined "intimacy" issues. (But I was allowed to hear the recording later ... go figure!!!)

Thanks Greg. Unfortunately, they don't' want to see the sound blanket so I could only think under the table. The room is awful for recording audio, one wall is all glass from the floor to the ceiling. I explained it to them and they don't care. I told them not to expect anything amazing in this case. There is no HVAC system.

[Kathy Smith]

Originally Posted by Roger Gunkel

Hi Kathy,

It would be great if you could come back on this to let us know how you get on with the Shures and the overall quality you managed to achieve.

Roger

The mics are coming today and I'm going to test them right away. I'm doing the recording tomorrow night. I'll let you know how it goes.