Microphone for recording a round table discussion

[Kathy Smith]

Thanks Richard. Yes, I didn't think any of the cubicle things would be effective in this case. I'm wondering about those ceiling panels. Would they be better than nothing on the ceiling?

[Paul R Johnson]

The two recordings sound exactly like they are - distant mics in a room with hard surfaces. Are either acceptable to you? If they are not, then you have to spend money. On equipment, treatment, people to work the kit etc.

We seem to be looking at a magic bullet to solve the problem, in any place the people are in the room.

If you treat the room, and turn it into an anechoic dead room - then you still have level changes to deal with if you have multiple sounds sources, each with different speaking voice levels.

Are we talking hundreds or thousands?

[Derek Heeps]

Originally Posted by Kathy Smith

Hi,

I've been asked to record a round table discussion and I'm wondering what would be the best way to handle audio recording. The people participating do not want to have to pass a microphone around form person to person and I'm not capable of micing everyone. The only mic I have is a shotgun mic (other than a lav) and I was thinking of putting the mic on a boom pole and a stand and having it be sort of suspended in the middle over the table. The microphone I have is Sennheiser K6. It will be like 6-8 people at the table. What do you think of this set up? Is there a better way of handling this?

Thank you
Kathy

A boundary mic 1/4 of the way along each table ( so 4 mics or one between 2 participants ) and fed into an Audio Technica Smart Mixer which will automatically open and close individual mics as required .

http://www.audio-technica.com/cms/mi...e0f0833b22a45/

These 4 channel units can be daisy chained if more microphones need to be added . Any good hire company will have them for modest daily charge - I used to use them to record conferences and they work really well .

Edit - they can be picked up used

http://m.ebay.com/itm/112166413659?_mwBanner=1

[Daniel Epstein]

I have a couple of Shure Fp-410's which can do an Automix. They have been replaced by this model .

https://www.bhphotovideo.com/bnh/con...C&A=details&Q=

I have used matching Lavs, booms, and table mics depending on whether you can mic individuals or just need general coverage.

[Derek Heeps]

That looks almost like a clone of the Smart Mixer !

[Greg Miller]

Originally Posted by Paul R Johnson

you still have level changes to deal with if you have multiple sounds sources, each with different speaking voice levels.

A gain adjustment in final mix is a lot simpler than magically removing room resonance and reverberation from a marginal recording.

I still say: let the client fix the room, then see if you can get an "acceptable" recording. If you can't, then it might be time to throw some money at the recording set-up. If I were Kathy, I'd be disinclined to spend any of my money to compensate for a room that the client knows is terrible ... unless the client is willing to pay for my new equipment.

[Greg Miller]

Originally Posted by Kathy Smith

Also, I came across interesting looking acoustic panels, what's your take on these:
Snowsound USA Acoustic Panels |

For a long time people have used panels made of Owens-Corning 703 high-density fiberglass, in various thicknesses (typically 1" to 2") and covered with various decorative fabrics. That would be a good and safe starting point for your panel search. There are plenty of published graphs and tables showing measured acoustical performance. To me, that's a lot more meaningful than a pretty brochure that says "Acoustic Comfort Inspired by Nature."

I'm pretty sure that in an earlier post I also suggested the products by Tectum. They have a very wide range of highly effective acoustically absorbent panels, in various materials and finishes. Again, they have extensive published specs and a long history of successful use going back at least 30 years that I'm aware of.

Regardless of your panel material, I don't see any advantage to having the panels hang down on cables, like the illustrations in the brochure. Your room has a low ceiling already. I would get panels that can be mounted directly to the ceiling. They will be much less visually obtrusive (which allegedly is important to your client). And probably much easier to install.

Don't forget that NYC has exceedingly stringent fire and safety regs. I strongly suggest you get a qualified architect to approve any final decision, just to CYA in case of regulatory headaches down the road. In your position, I would say "Here's a product with good acoustical properties; check it out," but I would not say "I recommend that you use this product." Maybe it's just me, but I try to avoid legal liability and lawsuits.

Finally, I'm a little curious because you are now talking about ceiling panels. Have you abandoned window curtains? Have you abandoned wall panels? What's the latest progress report?

[Kathy Smith]

Hi Greg,

The ceiling panels are in addition to the window curtain, wall panels and a carpet. I thought hanging ceiling panels would be less intrusive to the original ceiling and if they didn't want to mount panels in the ceiling directly, perhaps I could recommend the hanging ones if they would make any noticeable difference.

[Greg Miller]

Hi Kathy,

Well, I'm glad to hear that they're considering that much treatment! That will be a big improvement.

The mounting I'm thinking of would be to attach the panels directly to the ceiling using some type of screws (depending on the present ceiling construction). Of course if they remove them later, that would leave a lot of small holes (probably less than 1/4" diameter) to patch. With the cable-hung panels, you would still need to attach the cables to the ceiling, so presumably you would end up with a similar number of similar holes. I don't see any advantage in terms of mounting, and little or no difference in acoustical performance if the panel performance is the same.

I'd think thin panels mounted directly on the ceiling would have less visual impact. They could essentially just appear to be one continuous ceiling, just an inch or two lower, and slightly different surface texture, compared to the present ceiling.

And, by the way, what's the source of artificial lighting in the room? And what about ventilation? Would ceiling panels interfere with either of those functions?

When you evaluate panels, try to find a graph that shows absorption in different frequency bands. It's relatively easy to absorb high frequencies, harder to absorb as you get lower. That room is big enough to have some resonance at relatively low frequencies, so you want to be sure your panels have good LF performance. When you see an NC figure, that's an average of many frequency bands, but it doesn't tell you about specific frequency performance. To get rid of the LF resonance (and very long reverberation time) in that room, LF performance is really important.

I will note that some panels provide different LF performance if they are mounted an inch or so away from the hard surface behind them. You will find this data in amongst the acoustical specifications. In that case, you might end up mounting something like 3/4" furring strips to the ceiling, then mounting the panels directly to the furring strips. (I doubt that you could achieve a spacing this close with cable-hung mounting.)

Anyway, good luck with all of this! It's great that they're willing to consider rather extensive treatment (which is what they really need). It will be interesting to follow the progress of the project.

[John Nantz]

Before hanging anything on the ceiling one should find out what is holding it up and how much additional load it will accept, if any.

Based on the pictures, there are only two choices for holding up the ceiling:
(1) with very long beams that go from one end of the room to the other and that is a 40-foot span, or,
(2), cantilever beams in the 20-foot direction to provide a clear span with all glass at one end.
The glass windows are not a structural support and cannot provide any sideways shear bracing, either.

Option (1): To have beams that will span 40 feet they will have to be quite large, even with a very light loading such as a sloped roof. If there the space above is occupied then the loading would be even greater. Also, the bookshelf “wall” would have to be a structural wall with a short cantilever beam over the opening between the two rooms in order to support the 40-foot beam trusses. That darker-brown thing at the end of the book shelves could be covering a structural column support but then what is that black circle thing?

Option (2): The other way to support the ceiling is with trusses or cantilever beams, and the only way that can work is if there is a large room opposite the glass wall side. Ergo, this room would be part of a much larger building on the other side of the wall.

The dark vertical frames around the glass windows don’t appear to be substantial enough to provide significant load support.

Even just plain old fluffy Fiberglass® batt material weighs enough that it’s load has to be taken into account.

The ceiling support is a mystery and I’m very curious about what is holding it up.

More curiosity, are the black and white tables for hosting debate teams?

[Greg Miller]

John,

That sounds like very well-reasoned structural analysis. It must be an interesting building. And I agree about any added load, even if the total is only a few hundred pounds. I've advised Kathy more than once to get an architect involved, so she can avoid being responsible for any structural and safety issues. I think she has sense enough to follow that advice.

[John Nantz]

Thinking about this some more, there can be a third option which would be a combination of the first two.

Option (3): The darker-brown thing is really a column and it supports a beam above the book shelves, that’s why there are shelves there so they can ‘hide’ the thickness of the beam above. That beam cantilevers out and over the opening between the two walls. The outside end of that beam provides the support for the 40-foot beam that runs above the windows, in both this room and the one on the other side of the bookshelf partition/wall.

The outside 40-foot beam supports the ceiling joists (big ones for the 20-foot span) and/or beams on 10-foot centers with 2 x 12 joists @ 16-inch on center between the beams.

I’m beginning to think this option is the most likely scenario.

Question: Besides the question about heat and cooling outlets, where are the electrical outlets?
Guess they could wear heavy wool coats during the New York winter. Don’t think that fireplace could provide enough heat and there is no way to distribute it. Since this is at ground level, probably radiant heat via a heated concrete floor.

In any event, those glass windows would make it drafty as the heavier cold air swoops down and across the floor nearest the windows.

[Greg Miller]

I think the brown posts are load-bearing, so the beam has some support along its 40-foot span. I can envision steel bar joists on 24" centers, running from the 40-foot beam to the opposite wall. Twenty feet would be unexceptional for bar joists.

The photos show what appear to metal registers in the floor just in front of the window wall. That would be the logical place for heat, to counteract the natural convective draft in cold weather.

Maybe the fireplace is a facade, and it's actually an HVAC air return (or supply), with the other end of the system being beyond the bookshelves. Either way, there would be a heck of a breeze between the shelf end and fireplace end of the room.

I wonder what era this represents.

[John Nantz]

Greg - Over here we’re in earthquake country so many of our structures are made of wood whereas back east there is a lot of masonry, like the building on the other side of the fence.

Looking at Post #31 on my laptop I didn’t see any floor registers but if there are then the floor is probably a wood floor with a small crawl space underneath. Trying to get a floor vs outside grade comparison it does look like the floor might be slightly higher than the outside so with the floor registers and the hight difference that might indicate this is a wood frame building.

The brown poles are interesting because they’re inset from the outside wall. I was thinking they might be utility poles like what are used in an office to run phone and computer lines inside. If they’re structural, then they’re almost for sure supporting a beam above and it is cantilevered about a foot or so to the outside wall where to support the beam above the glass, so that idea works.

If there is a regular roof above then there should be some downspouts visible but I don’t see any. The east coast weather can generate some real downpours. (They wouldn’t put a downspout inside that support, would they?)

What era does this represent? That’s a tough one. In the late ‘30s early ‘40s there was some minimalist architecture, then again in the late ‘50s (at least in California), and again around the early ’70s (after the avacado/dark brown/orange-yellow period). Given the large glass panels (single pane???), I’ll take a guess that it’s late ‘60s to early ‘70s.

I’d like to know what Kathy has to say about this.

[Greg Miller]

John, click the thumbnail of the photo showing the bookshelf. The full-size photo clearly shows several floor registers, very skinny ones, pretty close to the window wall.

Yes, the ceiling extends out past the window wall a couple of feet. So something up there is clearly cantilevered over that long beam. (But the foundation probably stops at the window wall.) I'm still gonna guess it's steel frame. A 20-foot span supporting perpendicular 20-foot spans would call for some extremely tall beams. I think steel, and bar joists, are much more likely. No shortage of steel in the NE (at least before we started importing it from Asia).

Originally Posted by John Nantz

The east coast weather can generate some real downpours.

You don't get much rain in Seattle, do you? ;-)

Downspouts are sometimes interior. In fact on some flat membrane roofs, the drains and plumbing can be many feet back from the exterior edge. Although other "flat" roofs use scupper drains at the exterior edge ... clearly that's not the case here. I've been in one building (a meteorology building) where the roof drains come down through the office space, and are made of clear PVC, so the occupants can observe the precipitation coming down the drains. But no, I doubt that those brown poles are wasted for drainage. I think it's much more likely they are support columns. Of course the column could be an I-beam with a wire trough between the flanges.

I hope that glass isn't single-pane, or that place would be a nightmare to heat. But unless the windows are fairly new, it's likely that they are.

Kathy has been pretty mum about the details. Maybe she's afraid we will be tempted to go up to visit the place, stand in the room, clap our hands, and laugh at the long reverb time. Maybe we can post the photo online somewhere and ask the world, "Do you recognize this room?" If it's a really noteworthy building, some architect might know it. There can't be too many buildings in New York, right? ;-)