Microphone for recording a round table discussion

[Greg Miller]

It's a tough nut to crack. They want a room that looks stark and harsh ... it is going to sound stark and harsh. I'm glad they are at least aware of the problem and willing to contemplate some improvements.

You have to think in terms of surface area. Treating just one of the short walls, which is a very small percentage of the room's total surface area, will have a minimal impact on the room's acoustics.

Given that they aren't willing to change the long glass wall, I think the other long wall is the first candidate for change. There are various acoustical treatments that could be used. Certainly acoustical panels could be hung on the wall. Because of the amount of glass I'd suggest covering that long wall as completely as possible ... end to end, floor to ceiling. This could be done with something that is somewhat removable, like OC 703 panels. Or it could be a complete architectural refurbishing, by installing something like one of the Tectum products. Or it could be covering the wall with sound-absorbing ceiling tiles (properly spaced from the wall, with proper absorption behind them) but those are not as maintenance-free as a proper wall covering.

The next biggest area is the ceiling. It could also be covered with absorbing tiles with proper spacing and absorption, or with a Tectum product.

Of course either of the above will make some change in the room appearance, but some of the choices would at least keep the look of "a big white expanse."

Carpeting would help, but of course would not look like that beautiful wood floor. They may be very resistant to changing that. (I would be, if it were my floor!) Remember, surface area is key. Adding a 9' x 12' rug on that huge floor will make only a very small difference. If they keep the wood, that just makes it all that much more important to address the ceiling.

Treating one or both of the short walls would help somewhat, but again, they probably won't want to change the wood. They could install treatment on the wall between the bookshelves. That could be something like 1" thick 703 panels, manufactured to fit. It would not be immediately obvious, unless you looked closely. If the shelves are deep enough, there would still be ample room for books. (But they need to treat more than just this one wall!)

There is a lot of existing data for these various building materials, and a lot of formulas to help calculate reverberation time, etc. For that level of complexity you want to talk with an acoustician.

Of course any change is likely to involve building codes, fire and smoke ratings, etc. By all means make "recommendations" but don't put yourself in the position of giving them "specifications" because if you inadvertently violate some local building code that could come back to haunt you in a very big legal way. Before they make any permanent changes to the room they really should consult someone familiar with the regulatory aspects.

[Kathy Smith]

Thanks Greg. I know the glass wall is one of the biggest issues here. I'm pretty sure they just want to add/change decoration that would help with acoustics and not change any walls etc. This is a historical building and they will not alter it's original design.

[Richard Crowley]

There are a number of curtain and blind styles that would be quite sheer and translucent, to preserve the view but would cut down on acoustic reflections off the windows.

And/or, they could consider some wall-hangings on the opposite wall. Even some pure-white quilts would maintain the stark ultra-modern look, but soak up a lot of acoustic ambient reflections.

[Kathy Smith]

Originally Posted by Richard Crowley

There are a number of curtain and blind styles that would be quite sheer and translucent, to preserve the view but would cut down on acoustic reflections off the windows.

And/or, they could consider some wall-hangings on the opposite wall. Even some pure-white quilts would maintain the stark ultra-modern look, but soak up a lot of acoustic ambient reflections.

I can suggest acoustic sheer curtains but as for the opposite wall, hanging pure white quilts would be an issue because they project on that wall. They will not install projection screen.

[Greg Miller]

I'm a little puzzled here. They asked you for suggestions to improve the sound, but they are essentially unwilling to make any changes? Where would they put the "decorations" you mention, except on or in front of the walls? Certainly hanging two or three paintings (where, if not on the walls?) would not make a gnats bit of difference.

You've got three pairs of parallel reflective surfaces: a pair of long walls, a pair of short walls, and the floor/ceiling pair. You need to put absorption on at least one surface of a given pair. Again, since the long walls are the most surface area, that's the logical place to start.

Or you might try a triple-diffusion vacuum pump. If you suck all the air out of the room, the acoustical problems would disappear.

[Greg Miller]

Originally Posted by Richard Crowley

There are a number of curtain and blind styles that would be quite sheer and translucent, to preserve the view but would cut down on acoustic reflections off the windows.

Richard, could you please be a little more specific about these curtains. I'd like to educate myself a little bit on these specific materials. I'm a bit confused by your description. I thought "translucent" meant something like waxed paper, which lets light through but does not allow you to see objects on the other side ... to my way of thinking that would not preserve the view of the outside. Perhaps if you could refer me to some specific products I could understand what you're talking about. ... Thanks.

[Kathy Smith]

Originally Posted by Greg Miller

I'm a little puzzled here. They asked you for suggestions to improve the sound, but they are essentially unwilling to make any changes? Where would they put the "decorations" you mention, except on or in front of the walls? Certainly hanging two or three paintings (where, if not on the walls?) would not make a gnats bit of difference.

You've got three pairs of parallel reflective surfaces: a pair of long walls, a pair of short walls, and the floor/ceiling pair. You need to put absorption on at least one surface of a given pair. Again, since the long walls are the most surface area, that's the logical place to start.

Or you might try a triple-diffusion vacuum pump. If you suck all the air out of the room, the acoustical problems would disappear.

I'm meeting with them shortly to find out what the heck they want.

[Greg Miller]

There are some acoustical materials that would still look like a stark white wall ... but perhaps with a slightly different texture. They would probably be adequate as a visual projection surface. They could still end up with a stark white ceiling (a few inches lower than the present height), again with a slightly different texture. It's a question of what "appearance" they are trying to retain, and what they are willing to change, in order to gain intelligibility.

Sorry I'm no longer in New York. I would love to attend that meeting with you. Good luck!

[Dave Baker]

Or you might try a triple-diffusion vacuum pump. If you suck all the air out of the room, the acoustical problems would disappear.

She wouldn't get a recording then, sound doesn't travel through a vaccuum! :-)

[Greg Miller]

Originally Posted by Dave Baker

She wouldn't get a recording then, sound doesn't travel through a vaccuum!

Exactly! That's why the problems would disappear!

[John Nantz]

The discussion keeps going around room modification and that seems to be very arduous, expensive, and a lot of work. Back in post #43 Greg said:

Originally Posted by Greg Miller

Ya know, a few of us have mentioned separately-tracked lavs, and of course that's an impractical amount of complexity.

So, question: Why wouldn’t something like this work? Separate lav mic for each person and run into a mixer/recorder or mixer then into a recorder. Instead of having a person running the mixer, just set it up with the pots adjusted based on a test run ahead of time (asking each person to talk more or less like they would during the meeting and assuming the discussion would be cordial) and hide it under the table.

For the mics, on Amazon there is an Audio-Technica ATR3350 for $29 and there are many other lavalier mics out there. This was the first one I came across.

For recording, and this is where (for me) things really go into unknown territory. If mics like this would work (don’t know if phantom powered mics would be required), there are a couple options: an 8-channel mixer/recorder or, say, a 12-channel mixer where the recorder would be separate. There is a Tascam DP-03SD for $299.99 new/$199.89 used on Amazon. Search for “Korg D8 Digital Audio Multi Track Recorder” and there are several other multi-track recorders listed under “Customers who viewed this item also viewed”. There are ads for various Behringer models such as the 1202fx 12-channel mixer starting in the $110 -$120 range.

Would there be a problem with one person’s lav picking up the neighbor person speaking?

With regard to the room, the book shelves appear to be a room divider and not a wall. Looks to me like the divider doesn’t go all the way across the room and there is an extension of this room on the other side.

[Greg Miller]

You're right, this conversation has taken a few twists and turns.

Kathy, the OP, originally said she had only two recording channels; she later increased that and was willing to record at least three separate tracks. At one point she said there would be between 6+1 ppl, and 8+1; at another point she said there would be 13. But she clearly did not have enough capability to mic everyone separately.

That led to discussion of the "best of the worst" solutions (kind of like this year's US Presidential election). I think most of us agreed that boundary mics would be better than other "simple" options.

We then digressed into what effect the room acoustics would have on the result. Many of us felt the room would be "very challenging" at best, but Kathy seems to feel her recent recordings were at least usable for some purpose.

We are left with some unknowns here. We don't know the actual dimensions of the room. We don't know how many ppl were ultimately involved. And Kathy has never told us (despite being asked more than once) what the end purpose is for these recordings. Apparently the client is now thinking about improving the room; again, we don't know why! Does the client want better conference space? Does the client want to make more recordings? Etc.

Would actual multi-track recording be an option in the future? It would certainly be costly for Kathy. She'd have to buy (or rent) a slew of mics and some sort of multi-track recording machine. It would cost a heck of a lot more than her present outlay. So there's the financial question: it is worth it, in terms of how much she can earn from this client?

Also, does she want to deal with this much complexity, and mixing down a zillion-channel master? Is the added complexity worthwhile, again in terms of potential income?

How does the client feel about having a gazillion wires snaking all over the table? How many participants will be involved the next time? What if there will be 24 ppl? 30 ppl? 36ppl? Etc. etc. It starts to become physically and financially unwieldy.

To answer your specific question: every lav will pick up every sound in the room. A given lav will pick up its respective person the loudest, and everyone else at progressively decreasing levels as the distance increases. But in the final mix, you would use only one lav/track at a time, so that's as good as it gets.

Yes, clearly the book shelves are a partition between the room in question and the rest of the building. That appears to be the only visible walkway to get to the rest of the building interior.

In my opinion, the real problem is the room. If they want to record frequently in that room, I feel they really need to fix the room. Then it will be possible to get a more reasonable recording without one-for-one micing every participant. That will involve, at the least covering a lot of the long wall in some way ... either with permanent panels, change in construction, folding portable panels, etc. That will at least somewhat change the appearance of the room ... either for the duration of the shoot, or permanently. "Ye canna defy the laws of physics."

[Richard Crowley]

Perhaps not a viable solution to Ms. Smith's situation, but I remember a discussion in one of the audio forums I frequent (possibly this one, but probably another one). One of the people who produced this documentary on Thorium reactors as a clean and safe power source recounted how he hacked a bunch of little dirt-cheap audio player/recorders to serve as self-contained clip-on mic/recorders. They were apparently cheap enough that he put two on each person (for backup redundancy) and just let them run all day. Then he had a complete dialog recording from each person that could be downloaded and dropped into the timeline of his NLE.

You can see in many shots in this video the little audio gadgets that he hacked. They are clipped on to the shirts/pockets/lapels/collars of the subjects. To my ear, the audio from this very ad-hoc documentary is quite above average in quality despite the "cheap as chips" (BrEnglish) or "dirt-cheap" (AmEnglish) audio solution. Does anybody remember this discussion of how they did audio for this doco?

https://youtu.be/xIDytUCRtTA?list=FL...4X_6kqWtVYE4kQ

[Kathy Smith]

I'm sorry that I didn't say but I still don't know what the final purpose of this recording is. I don't think they know themselves. They were 13 people. At first I was told there would be 8 but then they said 13.
None of them have seen or heard the recording. I set their expectations really low. In the end they said as long as they get something that would be good enough!!! So, the fact that they want to improve things is based solely on the fact that I told them that the sound is not good. They just wanted to know if they could make little changes to make things better. They are not hoping to convert this space into a sound recording studio. They will not be holding conferences in that space. It's meant for occasional, intimate conversations over drinks, which will most likely end up on the web.
They are willing to buy a rug, hang stuff on the walls and perhaps hang a curtain on the glass wall but that's pretty much it. In the future, if they find themselves doing more and more events in that space they might rethink things but for now that's it. And yes the bookshelf is a half wall. They will not consider altering the space as it's a historical house.
As for using lavs on every person, it would be hard for me to do by myself. The way things are organized it's not a conference where everyone shows up and they start on time. This is more like people come and go in the middle of the conversation they get up to get drinks etc.
I will try to post a sample of the recording later.

[Greg Miller]

Nobody needs to worry about turning that space into a recording studio! They'd need treatment on all four walls and the ceiling to achieve that goal! Right now the reverberation time is longer than ideal even for conference room use. (By the way, can you give us the approximate dimensions of the room? I'm guessing about 30' x 15' x 10' high.)

There is a type of wood (or metal) trim called "picture rail." It comes in various contours, one of which is shown in these photos:
http://abeautifulmess.typepad.com/.a...81ef490970d-pi
https://s-media-cache-ak0.pinimg.com...a06820459f.jpg

You'll see it in a lot of art museums and galleries. Note the metal hanger shown in that photo, which can be hooked onto the rail at any point. The process is that you install the picture rail permanently on the wall, pretty near the ceiling, and paint it to match the wall. Then you use the hooks to hang things temporarily, without needing to make any further wall penetrations.

If your client mounted picture rail, at least on the long wall, and then got enough 6' x 2' acoustical panels to pretty nearly cover that entire wall, it would help a great deal. They could get custom panels with a color of their choice ... either to blend with the wall, or to complement it. And if they wanted to project an image at some point, they could just take down a few of the panels, to create a "projection screen" area of the wall.

Depending on the weight of the panels, they could be hung from the hooks using nylon monofilament, or braided wire, or paracord. If art museums and art galleries aren't offended by this hanging procedure, surely your client could stand to hang some *temporary* panels. Be sure to stress the "temporary" part ... get them away from their fear of "disfiguring" the room. When you take away the panels (and hooks), all that's left is a very unobtrusive piece of molding that pretty much looks as if it belongs there anyway.

They could also get some matching folding acoustical panels, which you could stand in a zig-zag pattern in front of the short wall behind you when you're shooting. Setup would be quick and easy, and it would look as unobtrusive as possible.

All in all, this might be less than the ideal amount of treatment that this room needs, but it's the best compromise I can think of at the moment.