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Old December 19th, 2012, 02:38 PM   #1
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Using a stereo mic- are they your choice as a sound pro?

Greetings.

I thought I'd start a new thread. I've gathered an enormous amount very useful information thanks to the contributors in this audio forum.

I've owned my one and only mic, an Audio-Technica AT-822 Stereo mic for the past several years. I think it has served me well, but as you can tell, I am newish at the audio thing, but like I say, learning every day. (I was even a bigger PITA on the video and cameras forums, but learned so much that I now feel safe when confronted with most cameras, which I generally rent if I need something high end.)

It wasn't until playing around with the Shure FP 33 mixer that I realized that the 822 has a real drawback, or I am just not familiar with the idiosyncrasies or stereo mics.

Here is what I've found: If you position the 822 directly in front of the sound source I.E. a person speaking, the sound (gain?) is quite low. However if you position the mike to the left or right side of the mic, the sound really bumps up (sorry for my bad lingo here). This makes sense since the stereo mic would have a left and right channel.

So my question is: why the dead spot when directly in front of the mic? When and why would someone use a stereo mic in professional audio world? Or would someone in the biz choose separate mic(s), and then mix.

My gut feeling is that they are more hassle than just dealing with a "mono" mic.
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Old December 19th, 2012, 03:12 PM   #2
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Re: Using a stereo mic- are they your choice as a sound pro?

One important thing you missed when you gathered your audio info .. spoken voices should always be recorded in mono
and positioned in the centre in your video or audio production.

Sounds like you're running into phase problems with your stereo 822, so you need more research then practice with stereo.
It's used for stereo sound effects, music recording eg: small choirs.

Read Jay Roses book, available now on Kindle .. http://www.amazon.com/Jay-Rose/e/B000APKOEM

Here, enter this you might win a good mono mic .. http://www.prosoundweb.com/sweepstakes

Cheers.
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Old December 19th, 2012, 03:41 PM   #3
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Re: Using a stereo mic- are they your choice as a sound pro?

Thanks Allan. I've just ordered the Jay Rose book. I've been really focusing on my sound stuff lately. Even if I have the luxury of hiring a sound person, I just want to know what's going on.
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Old December 19th, 2012, 04:12 PM   #4
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Re: Using a stereo mic- are they your choice as a sound pro?

I would guess that mic has an x-y configuration, each pointing 45-degrees to the side. For dialog, you could turn the mic 45-degrees and then select that channel as the source. (When you record on-center, both mics will have some mid and high-frequency roll off.)

Each mic component is probably cardioid though, which isn't ideal for dialog. One typically uses a lobar shotgun outdoors and a super- or hyper- cardioid indoors.

A stereo mic is best for recording ambient sounds and live music, though amplified bands are often mixed in mono so that the audience on the left and right extremes of the stage can hear the whole mix.

One can record Foley elements (footsteps, etc) in mono and place them in space using channel balance, delays, EQ, and convolution reverb. Even large orchestral scores are generally mixed to stereo or multi-channel from a large bank of mono mics placed near each instrument or group of instruments on the soundstage. (They will also typically have some mid and far mics that record the reverberant sound in stereo or better.)

A good rule of thumb is this: When recording one item, a mono mic works fine. You can place it and add the "space" in post. When recording multiple, concurrent items (like people and birds in a park), it's good to record in multichannel to capture them in their original space. That way, you don't move all the people and all the birds left or right as you pan/delay.
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Old December 19th, 2012, 05:34 PM   #5
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Re: Using a stereo mic- are they your choice as a sound pro?

Quote:
Originally Posted by Jon Fairhurst View Post
...A stereo mic is best for recording ambient sounds and live music, though amplified bands are often mixed in mono so that the audience on the left and right extremes of the stage can hear the whole mix...
I've used quite a few approaches to stereo mic technique; Jon's advice is good.

Frequently, for live performance, I'll have either a mono mix or multitrack recording of all the performer's direct mics, and a stereo mic in the audience both for their sound (applause!), and to mix in to provide some ambience and room sound. A directly miced musical performance can sound pretty dead without some reverberation/echo/delay mixed in. These can certainly be post EFX, but it's nice to have the choice of what it sounded like in the original hall with the audience.

IMHO, where stereo micing *really* shines, is as the only mic for a small acoustic ensemble where they have acoustic balance. Nothing beats it in a good room with this kind of performance, though some might reasonably argue with me about that. Placement is critical for this... I do quite a bit of this type of work.

And, as Jon suggests, general ambience recording...

But no, not for dialog recording. Here your best choices are a lav or a boom mic.
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Old December 19th, 2012, 07:01 PM   #6
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Re: Using a stereo mic- are they your choice as a sound pro?

Jonathan,

If the mic is really dead when perfectly centered, then you have something connected out of phase.

With an X-Y mic, each individual channel should be down about -3dB when the sound source is dead center, compared to when the sound source is off to the side by roughly 45 degrees.

Please give us exact description of every cable you are using between the mic and the mixer. For example, are you feeding that mic into just one channel of the mixer, or are you splitting it into two channels of the mixer? Either way, describe each cable in detail: type of connector on each end, as well as wiring details if you know them.

[I would bet that you are feeding the 822's XLR output, which is unbalanced stereo, into ONE of the mixer's XLR inputs, which are balanced mono. In that case, the mixer sees a signal which is the DIFFERENCE between the mic's left and right channels. When the sound source is centered, both mic channels are very nearly equal, so the DIFFERENCE is very nearly zero.] You need to cable it differently... OR use a mono mic for mono recording.
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Old December 19th, 2012, 07:21 PM   #7
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Re: Using a stereo mic- are they your choice as a sound pro?

The big issues here is WHAT are you recording and WHERE will it be used? As other have said, a stereo microphone is good for recording music (mostly acoustic music, not amplified bands) and for recording ambient background sounds.

Stereo mics are NOT a good choice for most of the sync sound we record with video. When you talk about putting the mic in front of someone talking, that is a PRIME example of where a stereo microphone is NOT appropriate. And you have demonstrated first hand why that is the case.

If I could have only one microphone and I were recording music and the occasional video, I would probably opt for a stereo microphone. But if I were doing primarily video, I would NOT choose a stereo microphone. I came to audio-for-video (and then to video) by way of many decades of audio experience, so I have many examples of both mono and stereo microphones. That provides me the relative luxury of never selecting an inappropriate microphone (like a single-point stereo mic) for something like dialog recording.

Remember that unless you are watching raw home-video of the nephew's 3rd birthday party, the track you are listening was almost certainly CREATED in post-production editing from multiple monaural sources.

Note also Mr. Miller's post. Without actually hearing and examining a sample, it is difficult for us to tell whether you are seeing the natural drop-off at dead-center on a stereo microphone, or whether you are seeing phase-cancellation from improper wiring and/or mixing. If the effect is only slight, I would say it is a natural phenomenon of most single-point stereo microphones. But if it is a profound drop (more than 6dB), then there may be other factors at play such as Mr. Miller is trying to walk you through. Of course, using the proper (monaural) microphone here would eliminate this potential problem altogether.
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Old December 19th, 2012, 07:40 PM   #8
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Re: Using a stereo mic- are they your choice as a sound pro?

Mr. Crowley:

He says when used dead on the "gain is quite low." To my mind, "quite low" is a lot lower than -3dB. I doubt that he'd even notice -3dB. (I'm betting that the dead-center sound quality is pretty thin, too, which would add to the "quite low" perception.) So I'm pretty confident that he's hearing phase cancellation between the two capsules. Remember that the 822 uses a 3-pin XLR for unbalanced stereo... to a neophyte who thinks "XLR = XLR" it would be easy to plug this into a mono balanced input and get "quite low" cancellation with a center source.
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Old December 19th, 2012, 09:58 PM   #9
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Re: Using a stereo mic- are they your choice as a sound pro?

Indeed. And Mr. Levin also says "It wasn't until playing around with the Shure FP 33 mixer..." which further suggests that he may have made the mistake of plugging the non-standard XLR output from the AT822 into a conventional XLR input of the mixer. He doesn't mention what cable (or camcorder) he is using.

But even wired properly (with the Y-cable that goes with the microphone), using a single-point stereo mic for something like speech/dialog is a significant compromise to optimal performance.
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Old December 19th, 2012, 10:22 PM   #10
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Re: Using a stereo mic- are they your choice as a sound pro?

Agreed, in regard to stereo recording of dialog.

Even if you create a proper mix of L+R, the pattern will be strange: cardioid in the vertical plane, but perhaps wider-than-normal cardioid in the horizontal plane. The actual result, I think, depends on whether it's an X-Y mic (like the OP's 822) or whether it's an M-S mic. In any case, there's no benefit to doing so, and it may well make the audio worse.

Besides, for a given price one proper mono mic should be better quality than a stereo mic (which is actually two mics in a single housing). So it's best to buy the proper tool for the job at hand.
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Old December 20th, 2012, 01:10 AM   #11
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Re: Using a stereo mic- are they your choice as a sound pro?

I tend to record all dialogue or speech in mono but use a stereo mic (sony ECM-MS957) for gathering stereo sound effects or buzz/wild tracks to add depth in post.

I also use stereo mics to do music or theatre/stage work but could just use several momo mics and pan them accordingly but as other people have stated it all depends on the job.
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Old December 20th, 2012, 11:55 AM   #12
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Re: Using a stereo mic- are they your choice as a sound pro?

Sorry for a very long reply.

First of all thanks for your time and patience fellows. I am realizing that not only good sound vital to any video/film production, it is also as complicated, or more so, than the video capture portion of a project.

Some of my colleagues believe that you just plug a mic in here, run a cable there, set a level and that's it. Obviously that's not true. I was always the kid who had to know how things worked, ended up with many clocks, motor things under my bed that I couldn't get back together, punished, but learned.

I take this approach to my production work as well, or at least I'm getting there. Up to now I've squeeked by with OK, sound, as you will see with my interview stuff with the Fearless Fernando video (see link below on my signature). I used the 822 mic for that and got lucky I guess.

I digress.

Let me describe how my initial set is:

As was noted by Richard and other contributors, the AT 822 mic came with a cable that was xor to mic, and the other end had 2- 1/4" mail plugs. I have never used those.

The mic was used initially to record solo acoustic guitar. I bought a standard Mogami 25' xlr male-female cable. (Man are these things expensive). I heard that Mogami was a decent brand with good warranty.

For my guitar stuff, I was running the mic, cable into a M-Audio Fastrack Pro USB interface to GarageBand on the Mac. Long story short, my audio kind of sucked, was never able to get consistent levels, final recorded material average....My head knows good sound, need to make the connect to MAKE good sound.

Fast forward to now, when a buddy of mine who is a sound guy for CBS lent me a Shure FP 33 to fool around with. And this is where I am now. The reason I am so into this is the realization of possibilities using a mixer, and not just for the added channels. Being able to feed sound in from another source is intriguing and the control aspect of each channel.

I digress again.

So to clarify, I have been testing the mixer with the stereo mic, a "standard" xlr cable to channel 1 on mixer. Pan dead center Gain set to 7 (2 o'clock) Master (unity?) set to 2 o'clock.

Left and right of mic a strong signal -3 but drops to -15 when dead center. Mic about 6 inches from me making steady sound (helloooooooo). Monitoring sound through headphone out on mixer.

So that drop is kind of in the center.

Apparently if I am doing interview stuff, this is not the ideal mic to use. I've read that cardiod or super cardiod or lav is the way to go indoors and a short shot gun outdoors. Mono all the way.

If any one has any additional comments, that would be great! My copy of Jay Rose's book will arrive in a few days, and spare your guys, hopefully, many more neophyte questions, and embarrassment.

I'm going to start a few new threads to address a few other basic ??'s if you dare.

Best to all.

Jonathan Levin
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Old December 20th, 2012, 01:01 PM   #13
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Re: Using a stereo mic- are they your choice as a sound pro?

If you are plugging the AT822 directly into a common XLR microphone intput, you will get extremely wierd results because the microphone was never intended to be connected that way.

Your AT822 microphone does not have a standard XLR output. It is a "stereo microphone". It is actually two separate microphones inside a common case. It has TWO outputs by definition.
It cannot be plugged into ANY standard XLR input and work properly. You have demonstrated that for yourself.
You MUST use that microphone with a properly-wired Y-cable to split out the left and right channels separately.

If you don't have a Y-cable with XLR male ouputs, then you must acquire or make one. Until you have the proper cable, you are wasting your time.
Note that you can't just buy any old "XLR Y-cable" it must be wired specifically for this microphone.
Or you could take your cable with mini phone plugs and use adaptors or re-wire it with XLR output connectors.
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Old December 20th, 2012, 01:56 PM   #14
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Re: Using a stereo mic- are they your choice as a sound pro?

Thanks Richard.

I think I've given up using the 822 for my intended purposes. I hear what you are saying about the x/y thing. From what I know pin 1 on the mic is the left and pin 2 is the right and the third pin is the ground.

I suppose in a pinch I could use the mic as is with the two channels combined thru my xlr cable with the Pan set to center on the mixer, but that still doesn't address the odd left-right issue with the mic.

I'm thinking this is like using a wrench to change a light bulb. Onto the right tool, right-time frame of mind.

All my channels and outputs thank all of you!

Jonathan
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Old December 20th, 2012, 02:52 PM   #15
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Re: Using a stereo mic- are they your choice as a sound pro?

I'm still not sure what your "intended purpose" is?

Please note that the AT822 is not a bad mic. But it must be used properly (with the proper stereo break-out cable). And it must be used for appropriate (stereo) applications. Speech/dialog/narration is NOT an application for any stereo microphone.

Pin 1 on any XLR (even for the AT822 non-standard wiring) is always ground. On a standard microphone, pins 2 and 3 are a differential/balanced pair of the (monaural) signal. The microphone preamp rejects any signal that is common to both 2 and 3. That is how a standard microphone system works to reject noise picked up by the cable.

But your AT822 has the independent left channel on pin 2 and the independent right channel on pin 3. And when you plug it into a standard microphone input, you are getting Left MINUS Right. That is why you are getting a big hole in the middle. What you are calling "the odd left-right issue".

No, you can NOT "use the mic as is with the two channels combined thru my xlr cable" because it is NOT "combining" them. It is SUBTRACTING them and giving you a very weird response.
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