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Mic phasing problems
Old 19th January 2013
  #1
Here for the gear
 
🎧 10 years
Mic phasing problems

I run a small radio studio in downtown Los Angeles...by stating this, there is no implications that I actually know what I'm doing.

Anyway...we have 6 mics in a small room.

We have bad phase issues. I assume the mics are poorly positioned or they're too close together.

Attached is a photo of our talk room. I was hoping to get some tips on how I can adjust the mics or the room to try to help with the phasing issues.

I have broadcast quality pres on each mic. An airtools VP-2 and two Vorsis M2 voice processors.

The sound is a thin, tinty sound, most likely from other mics picking up the voice of the other person. Shows where it's only a single host sound great, but obviously as we have to turn on more mics, the sound sucks.

Attached Thumbnails
Mic phasing problems-image.jpeg  
Old 20th January 2013
  #2
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tINY's Avatar
 
1 Review written
🎧 15 years

Do you have gates on the mics?

Have you tried switching the polarity of each mic as an assistant talked into it?




-tINY

Old 20th January 2013 | Show parent
  #3
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🎧 10 years
Quote:
Originally Posted by tINY ➑️

Do you have gates on the mics?

Have you tried switching the polarity of each mic as an assistant talked into it?




-tINY

I haven't tried that yet, but I can.
Old 20th January 2013
  #4
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tINY's Avatar
 
1 Review written
🎧 15 years

You absolutely will get phasing issues in a room like that if mics aren't kept tight to the "talent" and more than one is on at a time.

That said, the right combination of polarity reversal on mics could help when two or more are hot.




-tINY

Old 20th January 2013 | Show parent
  #5
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Quote:
Originally Posted by xxedgexx ➑️
I haven't tried that yet, but I can.
Ok, so the mics are directly across from each other. Let's say I hear a bad phase on the middle mic on the left side...would I adjust the phase of the bad mic, the mic directly across from it, or the mics on the left or right side?

There is a total of 6 mics, 3 on each side of the table.

Thanks
Old 20th January 2013 | Show parent
  #6
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🎧 10 years
Quote:
Originally Posted by xxedgexx ➑️
Ok, so the mics are directly across from each other. Let's say I hear a bad phase on the middle mic on the left side...would I adjust the phase of the bad mic, the mic directly across from it, or the mics on the left or right side?

There is a total of 6 mics, 3 on each side of the table.

Thanks
Yeah, I played around with the phase of all the mics while show hosts were talking and it seemed to help a little bit, but I guess there's no replacement for bad mic technique. It's hard to explain this to guests though. They seem insistent on ignoring anything I say about talking close to the mic.
Old 20th January 2013
  #7
Gear Guru
 
1 Review written
🎧 15 years
DI

Slit their throats and insert waterproofed lavalier mics....

Is the ceiling overhead absorbent?
A layer of absorbent on the table should help. Thick felt or acoustic foam topped by robust fabric.
Taken to extreme you could have say a perforated stainless steel table top.
Are the mics all cardioid? SuperCardi's have an unfortunate pickup lobe at 180 degrees.
Close of course. Popshields all in good condition and not too thick?

DD
Old 20th January 2013
  #8
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Rod Gervais's Avatar
 
🎧 15 years
I am curious why you would post this here instead of a forum that was geared towards answering this question...... this forum is all about studio design/construction - not that there aren't people visiting here that know about mic techniques - but this forum is not geared towards such things.

Rod
Old 20th January 2013
  #9
Deleted e479b20
Guest
In such situations a so called automixer can help a lot. There's one built into the SD788 or try the classic

Shure Americas | Intellimix

Quote:
This eight-channel automatic mixer features the Shure patented IntelliMix, which activates only microphones being addressed, minimizing poor audio caused by multiple open microphones
Old 20th January 2013
  #10
Lives for gear
 
🎧 5 years
Nobody's mentioned the studio walls. From the photo, it sure looks like a lot of reflective surfaces. Owens 703 is incredibly cheap and effective, and there are lots of ways to cover it.

And you can pick up more absorption, if you've got standard Home Depot acoustic ceiling panels, by replacing them with real acoustic ones. The kind made out of an inch or so of fiberglass.

And those mics... exactly what kind are they? Normal broadcast announce mics aren't highly directional, because that would emphasize proximity effect for announcers who tend to eat the mic anyway.

Given all that, you'll still have some phasing when all the mics are live. Careful mixing by someone watching the participants, or an automixer, will help.

Or don't treat anything, don't change your mics... but do record multitrack. Then sort it out in post, bringing up only the mic for the person who's got something to say. It'll be more work but give you the best sound. And, um, it's what this forum is supposed to be about.
Old 20th January 2013
  #11
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Brent Hahn's Avatar
 
1 Review written
🎧 15 years
First off, if the mics are stationary (looks like it in the pic) you're getting leakage, not phasing.

Next, as Jay pointed out, your walls are way too live. Guy on the right talks, it bounces off the left wall and straight into all 3 mics on the left. With extra distance, for extra badness.

Another acoustic culprit is those cafeteria tables -- big hard bouncy surfaces. Not much you can do about that, but you definitely can hang a "cloud" over the whole deal -- an open frame with a big fat layer of OC 703 in it, hanging as low as possible, to keep the sound from ping-ponging between the tables and the ceiling.

Also, if you're compressing the individual mics, don't. Math-wise, you're effectively driving the leakage up. But do compress/limit the entire 6-mic buss. That way, when one person is talking and the compressor kicks, it reduces the leakage from the other mics.

None of the polarity business previously mentioned makes any sense to me, but hey, can't hurt to try it.
Old 20th January 2013
  #12
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minister's Avatar
 
🎧 15 years
I find it interesting that this gets posted in an Acoustics forum and they suggest looking at the mics and polarity. It gets moved to the post forum where folks suggest looking at the acoustics.

I agree with Brent, you are experiencing leakage, not phase. Multi-track this and sort it out. But also, deal with the room, the table and the arrangement of the people talking. Try putting some soft absorbative fabric on the table.

Flipping polarity doesn't seem like much of a solution to me either.
Old 21st January 2013
  #13
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🎧 10 years
I apologize if the title of this post is misleading. I assumed that a lot of my issues could be room/acoustics related and that's why I put a post in here.

I have no multitrack capabilities. This is a broadcast setup using a broadcast console. Pretty much has only two buses....it's not the same as a recording studio console.

I'm sure the room has major issues. We've done almost nothing except for a few wall panels. God, I'm hearing this one mic right now and it's killing me...leakage definitely does way more likely...

Also, we use like every mic combination you can think of for broadcast. Two PR40's, one EV RE27, Shure SM7B, EV RE320, Beyer Dynamic M99.

Ceiling padding is something I always wanted to do. The walls are just drywall. On the side you can't see, we have just wall panels.

The tables are garbage picnic tables like you said. Thanks for the suggestions. I'm sure there's a lot we can do just re-enforcing the room.

So I kind of just proved everyone's theory. If I turn up mic 5 while mic 6 is talking, I hear table sounds.
Old 21st January 2013
  #14
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tINY's Avatar
 
1 Review written
🎧 15 years

And when that "leakage" is combined with the primary, you get phasing issues...

Now that we got kicked out of the acoustics section: in a room like that, you probably want to make every wall dead, at least from 2 feet from the floor to the ceiling. In conference rooms at offices, you will notice that one of every of the parallel surfaces is deadened. The bounce off of the table and two of the walls helps people in the room hear. You don't want your mics to hear anyone except who is in front of it. So, you need to deaden all the walls, and possibly parts of the table.




-tINY

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