Microphone for recording a round table discussion

[Kathy Smith]

Here are two photos of the room this will be recorded in. The room will only have one or maybe two tables and there are things on the shelves now. I also believe there are vertical blinds on that big glass window. Not sure if the images help but any ideas what else I could do to that room to improve the situation? If I can convince them to use the sound blanket where can I put it so it's not in a frame? I will be shooting from where the fireplace is.

[Greg Miller]

That's looks like a terrible room for sound recording! Hard to imagine anything worse. One glass wall, the other walls are hard, the walls are probably parallel (can't tell for certain from the perspective of those photos). The ceiling is hard, the floor is hard, there is not even any upholstery on the chairs. The room is even ugly and austere to look at, the chairs look terribly uncomfortable ... shoot the architect!

Cover all the glass with sound blanket, if possible cover some of the other walls as well. Carpeting on the floor wouldn't hurt.

I know, "I can't do that." So it's going to sound terribly live and audio quality will suffer. You cannot defy the laws of physics.

Mic each person with a lav, record them all on separate channels, mix accordingly. I know, "I can't do that."

If they want this just for archival purposes, it might be intelligible. Certainly nothing that I'd want to air at a later date.

Please excuse my bluntness. I've just gotten done with a client who ignored my advice, gave me a garbage recording, and expected me to "fix it in post." I made it better, but IMHO it still sounds sub-standard. I hate being associated with stuff like that.

[Rick Reineke]

Looks like an acoustical nightmare. Hard floors, ceiling, windows. You'll need quite few sound blankets. If you could rent a large piece of carpeting to cover as much of the floor as possible. If you could put some sound blankets on the walls and windows... but if you're relying on natural available light, the blankets will be an issue with that. In my experience, many of those type of rooms, the HVAC system can't be shut down in individual rooms, so extraneous HVAC noise may be another issue.

[Roger Gunkel]

Yep I agree with Rick and Greg, an acoustic nightmare. Make sure that they are completely aware that the audio will not be good because of the room acoustics then at least they will know what to expect. If there are vertical blinds on the windows now then they may give a small amount of respite. You should see if you can angle the blinds to stop direct reflection of sound from the glass. You could also ask them if there are any alternative chairs available with soft backs to help reduce reflection.

I think that the boundary mics are the only type likely to give any sort of usable sound apart from the iimpractical solution of individual lavs. You could also try a reverb remover in post production, which I have had limited success with on some church sounds. Some eq tweaking in post may also help as a lot of room reflection is at the lower end of the voice frequency range.It may improve the sound at the expense of making it somewhat middly.

EDITED TO SAY you could put the acoustic blanket on the wall behind you for another minor improvement and I can't see them objecting to that as it will be out of shot.

Roger

[Greg Miller]

I largely agree with Roger, with a few additional thoughts.

If the windows had actual fabric drapes, especially if they were lined, that might help somewhat. My experience is that thin hanging vertical blinds are insignificant; in fact they are often made of hard plastic strips which are acoustically reflective.

Yes, most room resonance is at the lower end of the speech frequency range. (Standing waves are largely to blame.) That specific room looks so live that I suspect the reflections extend to higher frequencies as well. I'll bet if you stood in that room and clicked your tongue, or said "tsk, tsk, tsk" you would hear distinct reflections of those high frequencies, too. That will smear the consonants and hurt intelligibility.

And Roger has an excellent suggestion: be sure to warn the client ahead of time, so that they are mentally primed to blame the room acoustics, and not you, if they are disappointed by the recorded audio.

[Jon Fairhurst]

There are audio systems, generally for bigger venues, where each speaker has a box and goose-neck microphone with a button on it. Only one or two mics can be enabled at a time. Something like that could work, as they'd be inches from the mics. I'd imaging that you can rent these systems.

A nice thing for the moderator is that you ensure that only one person speaks at a time. (Why don't we have these for presidential debates?) The difficulty is that people forget to use the systems and without training, they use the mics badly - either eating them or not addressing the mics at all. For this sized room, it would be especially hard to get people to remember to press the buttons - there's nobody in the back row to shout, "I can't hear you!"

So it's a long shot. But if the attendees and moderator got training before the event and would be disciplined enough to use the system reasonably well, you could get good results, even in that room.

https://en-us.sennheiser.com/integra...-equipment-adn

If this approach is a viable option, I wouldn't shop for specific products. I'd call the rental houses to learn about what they have.

Probably the biggest variable would be the moderator. If the person is conscientious and willing to ask people to use the mics and coach them in proper use in real time ("please use the mic system." "Please speak about six inches from the mic.") then it could be quite good. If the moderator can't be bothered, it could be a complete fail.

[Paul R Johnson]

Boundary mics handle this so much better than other types so they'll probably work pretty well. After all, they are the choice of police station interview rooms where all surfaces are parallel and hard.

My own experience is that in meetings that are real as opposed to staged, the participants forget any guidance you give them on technical matters and will constantly talk over the top of each other. It is, exactly what it is.

Any form of boom is a real non-starter, because booms are reactive, so the vital first few words is always missed as the boom op works out who is talking, and gets there, only to find then the person at the opposite end reacts and he spends the session waving around, which is also very off-putting!

[Jon Fairhurst]

I tend to agree, Paul. I've used a delegate mic a number of times as part of my day job. I'm hyper-aware of audio presentation, so I do okay. Other attendees? Not so much. Without an attentive and gracious moderator, it's a fail. That said, this is the best way to handle open discussion meetings in very large rooms.

My concern about the boundary mic solution is the limited number of mics and channels. If the distance is too large, the far-away speakers will come through poorly. My experience with conference room mics is that 6 feet is the cutoff point. The sound might not be great at 6 feet, but it's easy to understand the speaker. Further away and low-signal, ambient sounds, echo cancellation, and noise reduction make communication difficult. In teleconferences, the person in the fourth chair or so ends up standing and speaking loudly to be heard over the phone. One might do a bit better with a clean, uncompressed recording and processing in post, but there would still be a big quality drop off after 6-8 feet.

[Graham Bernard]

Horrid.

OK:

1/- Move room/venue

.... If not acceptable

2/- Price-up pro audio company you know can do the job and get quote and inform client of extra cost.

. . if not acceptable

3/- Provide your solutions from what you've read here. This way, it leads client into knowing just what to expect and how you'd go about making a solution. Jon's experience might then be well heeded and registered by the client. You'd have paved the way. In my opinion you'd look both professional and caring towards your client's wishes.

[Greg Miller]

Kathy, a lot of us (including myself) are giving you rather pessimistic comments. I have been speaking from the perspective of getting a "studio quality" recording, or at least a "good clean" recording. I tend to think in terms of the best quality voice recording, within reason. That may be an overly narrow expectation.

In retrospect, I don't think we know the end purpose of this recording. And that really matters. Does the client hope to incorporate it in some sort of low-budget documentary? Will they use it for a training video? Or is it just for internal documentation and archiving?

If the room sounds the way I imagine it does, I would hope the audio doesn't end up on a big screen. If it's just for archival purposes, I think it should at least be intelligible.

You originally said there would be a maximum of eight people. The table in your photos appears to be roughly four feet wide and eight feet long. So you end up with four pairs of people facing each other across the table. Two adjacent pairs make up a group of four people. There are two such groups of four. Put one boundary mic in the center of each of those groups. Then each person should be about three feet from the nearest mic.

In a wonderfully dead and quiet room, the above arrangement would yield pretty decent audio. In your room, there will be some reflections, the voices won't be pristine, but they certainly should be intelligible unless ...
(a.) people mumble badly, or
(b.) the room noise is uncommonly loud.
Keep your fingers crossed that neither one of those situations exists.

Just to fill in the missing detail, can you tell us what the client ultimately wants to do with the recording?

[Paul R Johnson]

I work mainly in theatres, and without any doubt at all, the most common mic for picking up the actors on stage is the boundary type, usually PCC rather than PZM. For conferences I have a kit of table mount condensers - 12, on vibration reducing mounts. So each person, or perhaps a side by side pair of people have their own, and then the sound op is kept busy identifying who is speaking and reducing the level of all the others - never to zero to cover interruptions, but low enough to stop the nasty comb filtering effects that creep in with multiple mics close together. Where groups sit around the table - either circular, oval or rectangular or square, boundaries work again - and on long tables, one omni boundary per four people facing each other works, adding another for each extra 4 people. Boundaries are less prone to comb filtering, but it still can happen. With a recording, you can sort this in post - so not really an issue. For group work - with minimal kit, you can't beat them.

[Jon Fairhurst]

One thing to keep in mind with a boundary mic would be to avoid papers and typing if at all possible. Any sound right on the table will be loud.

We have a Bartlett stage mic for an annual young kid drama camp. The first year we used it, there was a western theme. They put straw all over the stage. Crunch, crunch, crunch. The director didn't think much of our mic choice. This summer, the concrete stage was clear, and people were very happy with the results. (I didn't hear the performance either time, so the results are hearsay.) The other improvement was that the loudspeakers were allowed to be in a better position this year, so we could use more gain.

Fortunately, you don't have a PA system and feedback to worry about. You can turn the thing up until it clips. (FWIW, the Bartlett mics have very low noise.) But you do have to worry about papers, typing, finger tappers, etc. But whatever method you use, you can bet a panel member will figure out a way to mess it up.

"Hi. I'm Chris. And I'm mumbling quietly into my hands while crunching on potato chips with my accent from the old country. I've now turned my back to the mic to walk far away from it where I will read an important and very long poem while performing a brisk physical activity with the cellophane potato chip bag. Also, sorry, I have this really bad cold. Sniff. Cough. Crunch..."

[Greg Miller]

Ya know, a few of us have mentioned separately-tracked lavs, and of course that's an impractical amount of complexity. But here we are advocating using two boundary mics, which are more or less one mic for a group of four people. (Of course each mic will pick up all eight people, just at different levels.)

In reality, it would not be any worse to combine four lavs into one channel, and four more lavs into a second channel. Each channel would have four people {fairly close} and four other people {fairly distant and inaudible}. The final "four into one" mix would certainly be no worse than a boundary mic. And you'd end up with closer micing, a lot less tabletop noise, and less noise from mechanicals in the room.

You could probably get acceptable results from relatively inexpensive lavs ... some specific models have been recommended in other threads in this forum. Of course you'd end up with everyone plugged in and tethered, with wires to get tangled. I'll bet the audio would be as good or better compared to boundary mics ... even if it's a fairly unconventional setup.

Oh, wait ... did someone rule out lavs back at the beginning of this exercise? We still don't know the intended final use for this recording, either.

[Greg Miller]

Re my post above:

Before someone mentions phasing issues between the lav mics, the setup I described should not violate the "three to one" rule. When a given person is speaking, his mic would be about 8" from his mouth. The mic on the person seated next to him would be at least 24" from the speaker's mouth.

You could improve on this if you distributed the mics on alternate channels. Then, when a given person is speaking, the mics nearest to him would be on the opposite channel, so they'd be potted down in the final mix. The nearest mic on the same channel would be at least 48" away from the speaker's mouth. That should make phasing issues non-existent.

I think the audio would be a little better than with boundary mics, because any given speaker would be picked up by a mic about 8" from his mouth, rather than at arm's length. Still, the complexity, and the tangle of visible wires in the shot, probably do not make this a better overall solution.

Meanwhile, I think Kathy's shoot was last night, so I'm eagerly awaiting her report on the results.

[Kathy Smith]

Thank you everyone for your help. The shoot happened on Friday and I was just able to look/listen to the recording this morning. It seems that the mics picked up everyone OK, everyone is intelligible but as everyone knew the acoustics of the room were horrible. The client was aware of all of this so no surprises there and they were OK with it. I put the mics on the rubber mousepads but they still picked up noises such as rustling paper etc.
They have asked me what could improve the acoustics in the room without destroying the look of the place. I suggested filling the bookcase with books, getting a big rug and what else can I suggest? The windows can't be covered and anything "ugly" that I add would have to stay out cameras sight. Would renting acoustical panels and placing them on the side where the camera is bring any significant improvement? The windows do not have vertical blinds. They have a mesh curtain which has very big holes in it, about 0.5inch squares.
What can I suggest?