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Old December 20th, 2012, 05:01 PM   #16
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Re: Using a stereo mic- are they your choice as a sound pro?

Hi Richard,

Thanks again for your help.

My intended purpose would be for interviews, indoor possibly out door. Single person. As you mentioned, not the right application for the 822 stereo mic. So the Y splitter from guitar Center wouldn't do it?

"I was unable to identify that product on the Live Wire website. There is no information disclosed about how it is wired, but I would wager 100:1 that it is NOT wired correctly for what you need. Repeating: this is a NON STANDARD wiring and you cannot use commonly-available adapters with it."

I'll look into Redco for an adapter. When I communicate with them, what exactly do I tell them I'm looking to have made?

I know that this is not the ideal mic at all, and that something like a Senheisser MK66 or 64 cardiod would be more suitable for my purposes.

I just found a ton of info that I really need to study here: Educational Articles - Online booklets and bulletins

My head is spinning.......
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Old December 20th, 2012, 11:27 PM   #17
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Re: Using a stereo mic- are they your choice as a sound pro?

Most microphones that use an XLR connector have what is called "balanced" signal.

Pin 1 of the connector is used for shield/ground, and carries no audio.

Pins 2 and 3 carry the audio. The two pins have equal voltage amplitude, but opposite polarity. If, some given instant, the microphone is seeing positive air pressure, and pin 2 happens to be +.003 volts, then pin 3 would be -.003 volts. If, at another instant, the microphone is seeing negative air pressure, and pin 2 happens to be -.027 volts, then pin 3 would be +.027 volts. Maybe you can visualize why it's called "balanced." (It's the same as the RF on a half-wave dipole antenna, but we won't go there...)

A typical mixer using an XLR connector has a balanced input. It subtracts the voltage on pin 3 from the voltage on pin 2, to obtain the total audio signal. In the first example above, the mixer would see
(+.003v) - (-.003v) = +.006 volts total (corresponding to a certain amount of positive air pressure at the mic). In the second example above, the mixer would see
(-.027v) - (+.027v) = -.054 volts total (corresponding to a certain amount of negative air pressure at the mic.)

The purpose of balanced wiring is to make the system immune to electrical noise. Let's imagine the microphone cable happens to be subjected to a strong electromagnetic field. Let's imagine that the field induces some voltage on the two microphone wires. (Actually, with shielded wire, noise is a minimal problem, but let's keep imagining...) OK, since the two mic wires are spiral twisted around each other inside the cable, they will receive the same amount of induced noise. Let's assume that both wires therefore pick up +0.077 volts of noise. The mixer sees
(+.077v) - (+.077v) = zero volts, so the system is immune to this type of induced electrical noise.

Now here's the problem with the 822. The XLR connector is used in a very non-standard way. Pin 1 is used for shield/ground. Pin 2 is used for left channel audio (not balanced) and pin 3 is used for right channel audio (also not balanced). If the two microphone elements are exactly and perfectly matched, and you record someone who is exactly centered on the mic axis, both elements will generate exactly the same voltage and the same polarity. So the voltage on pin 2 and pin 3 will be exactly equal.

So let's imagine both of the mic elements are responding to a positive air pressure, and both channels are generating +.045 volts. The mixer will see
(+.045v) - (+.045v) = zero volts. In other words, the mixer will subtract or "null out" the sound from the two channels of the mic, exactly as it nulls out induced electrical noise. Of course the elements are not perfectly balanced, and the sound source is not perfectly centered, so there is a slight difference in the left and right channel signals, and that difference is what you're hearing as "very weak" audio.

If you want to use the 822 only as a mono mic, feeding into a mixer with a normal balanced input, then the cable should be as follows:
MIC pin 1 >> MIXER pin 1 and pin 3.
MIC pin 2 >> MIXER pin 2.
MIC pin 3 >> MIXER pin 2.
Note that you're simply connecting the microphone's left channel (pin 2) and the right channel (pin 3) together, and feeding them to pin 2 (the "non-inverting" input) of the mixer.

You also need to be absolutely, completely, 100% certain to check, verify, and double-check that the mixer is not feeding phantom power to the mic jack. Phantom is used only for balanced condenser mics. If you feed phantom (which might be as high as 48 volts DC) to the 822, the mic will become an instant paperweight. And believe me, some day you'll be in a hurry, and you'll do just that. That's just one more reason to use a proper, balanced, mono mic for your application!

Note that if you use that cable some day for some normal balanced mic, it won't work at all and you'll end up pulling out your hair.

And of course if you wire the 822 as shown above, it really won't have the correct pattern for dialog, and the recordings will be less than ideal. (But hey... somewhere in the world, someone is trying to haul elephants in a Volkswagen. Some people just like to defy established experience.)
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Old December 21st, 2012, 05:43 AM   #18
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Re: Using a stereo mic- are they your choice as a sound pro?

Adding a note to Greg's excellent explanation, an ordinary XLR-F - > 2x XLR-M "Y" cable won't work to split the mic in order to send this mic to a pair of the mixer's conventional XLR inputs for stereo. The outputs of this mic are unbalanced and need to be treated as such. You'd need an adapter 'Y' cable made up that connects ...

XLR-F pin 2 to left XLR-M pin 2
XLR-F pin 3 to right XLR-M pin 2
XLR-F pin 1 to BOTH left and right XLR-M pin3
and
both XLR-M have their pin 3 shorted to pin 1 to unbalance the mixer's input.
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Old December 21st, 2012, 12:29 PM   #19
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Re: Using a stereo mic- are they your choice as a sound pro?

Steve, Greg, Gary, Richard, Seth and John.

Thanks so much for your input (no pun intended.)

I'm thinking of retiring the stereo mic for the time being. I'd just like to KISS (keep it simple stupid).

The difference between me and you guys is that you know what you are doing. I'm getting there.

I am even thinking of selling it if there is any interest, and get what I need in for my production purposes: interviews, and so on.

From what I've read, it sounds like I will be looking at both the following:

1) A hard wired lav of some sort. I do a lot of work in hospitals, and with all their equipment, I don't need the added RF headaches of wireless, at least for now while I'm learning and juggling and acting as a one man band.

2) Something like a Rode NTG-3, or Senheisser ME 66/64 Or some other Super Cardiod.

Jonathan
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Old December 21st, 2012, 01:35 PM   #20
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Re: Using a stereo mic- are they your choice as a sound pro?

It's quite possible that your stereo mic is capable of giving you really nice audio quality - so retiring it seems a bit counter productive - as having more mics to do different things is very useful.

You just need to get into your head the concept of stereo mics needing two mono channels, one usually panned left and the other right. Most non-DSLR cameras have had two inputs for many years now. If you use a stereo mic paralleled cable wise to make it 'mono' then that's fine. In fact, why not just make up two adaptors as people have detailed above (which anyone who can solder can follow as pin numbers are on the pins!) then you can have a short male to female XLR that can plug into any socket to give you mono. The other would have a female XLR one end and two male XLRs the other - this would go into a two channel (stereo) input device.

What you have accidentally done is produce something like the circuit inside cheap karaoke machines - these do exactly the same thing to a stereo signal to get rid of the centre components - usually the voice. If you listen again to your recordings you'll probably also detect that they sound very thin and on headphones, have a kind of 'hole' in the middle when you close your eyes and imagine what you can hear.

Most professional stereo one piece mics have a 5 pin XLR, not 3 - making the mistake you have less likely because ordinary cables don't fit!
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Old December 21st, 2012, 04:36 PM   #21
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Re: Using a stereo mic- are they your choice as a sound pro?

Ok. I'm really excited and making a bunch turkey noises like Curley on the Three Stooges!

I gave Redco Audio a call and spoke at great length with Chris. (Thanks for the lead, Richard Crowley!!!)

Very nice fellow, I went over what you guys wrote, and since I take decent photos, good video, good at woodworking and make really good BBQ'ed ribs, soldiering wires isn't something that I want to fuss with, especially since I'm dealing with sensitive audio stuff.

So, they are going to build me two types of cable, wired to the specs per Steve and Greg's suggestion. Actually, Chris knew straight away what I needed.

One cable will be a mono cable so that I can plug in to one channel, basically turning my stereo mic into a mono combined L+R input device.

The second cable, which he said is the preferred method, so that it can be used as a true stereo mic, is a Female xlr to dual male xor (two separate channels). I guess I would then use the pan controls for each channel and pan one channel hard left and the other hard right.

They know all the solder doodle stuff, and both cable cost me about $40.00US plus shipping. A bargain in my book to get this the way you guys have been so patiently trying to pound into my 56 year old head.

Agin, I thank you for your time and suggestions and if you have any more comments about what I just did, please post them.....here.

Happy holidays all.

Jonathan
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Old December 24th, 2012, 07:18 PM   #22
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Re: Using a stereo mic- are they your choice as a sound pro?

Quote:
Originally Posted by Jonathan Levin View Post
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. 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.
You don't use a putter in a sand trap. You don't drive with a wedge. An X/Y stereo mic is not a good choice for dialog for the very reasons you have described; square peg, round hole. If you want to use a stereo mic on dialog try a M/S mic with a front facing capsule and a side facing figure of eight. Still a bit of a challenge, especially when you're working the boom between two or more people because, if you intend to unfold the M/S into stereo, you have to be aware of left and right and swinging the mic can cause some really wacky sound field shifts.

The Neumann RSM 191 is a killer stereo mic, BTW. Here's a review I wrote some time back.
https://www.dropbox.com/s/haka1tz53c...nn_RSM_191.txt

Regards,

Ty Ford
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Old January 13th, 2013, 12:28 PM   #23
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Re: Using a stereo mic- are they your choice as a sound pro?

Greetings everyone.

Well my new cable/adapters arrived from Redco. I've had a chance to test them out with the AT 822 Stereo mic and Shure FP33 mixer and all I can say is WOW. What a difference! Best 30-40 dollars I've spent in a while!

The first thing I noticed with both the mono and stereo adapters is that there is no longer much of a dead spot when speaking directly into the mike!

The other thing I noticed is with the gain set at about 8, the meters only get to -10 to -7 with mike placement about 12" away from mouth. Does this seem normal? All inputs are set to MIC level.

Thanks to all of you, I now want to re-record everything I've ever done! I think I'm getting closer to better audio all the time, thanks to all of you.

I'll probably get the Y XLR-Mini output adapter so I can use this set up with my Canon HV30.

I am currently looking into Lav options and short shot gun and I think I'll be in real good shape, unless I get a camera that has xlr inputs, then I'll be in real good shape.

Jonathan
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Old January 13th, 2013, 12:56 PM   #24
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Re: Using a stereo mic- are they your choice as a sound pro?

Quote:
Originally Posted by Jonathan Levin View Post
The first thing I noticed with both the mono and stereo adapters is that there is no longer much of a dead spot when speaking directly into the mike!
PLEASE REMEMBER that this is a STEREO microphone!!! When you say "speaking directly into the mic" if you mean that you are in "front" of the mic ON AXIS with the microphone you are NOT "speaking directly into the mic". You are, in fact, speaking "off axis" into TWO microphones, NEITHER of which is aimed at you. You can experiment by slowly turning the microphone to discover what "directly" means for the left channel, and what "directly" means for the right channel.

Quote:
The other thing I noticed is with the gain set at about 8, the meters only get to -10 to -7 with mike placement about 12" away from mouth. Does this seem normal? All inputs are set to MIC level.
Assuming you are referring to the channel level knobs on the FP33. Assuming you are talking about the meters on the FP33. Assuming you have good batteries or power for everything.

You didn't state whether you were talking about one or the other channel (or both) (REMEMBER YOU HAVE A STEREO MICROPHONE). You didn't state where the pan pots were set or the master level control. I agree that running the channel volume at 80% is NOT normal. But all of these issues are somewhat more complicated by using a stereo microphone instead of a conventional microphone.
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Old January 13th, 2013, 04:00 PM   #25
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Re: Using a stereo mic- are they your choice as a sound pro?

Hi Richard.

Loud and clear on the directionality of the mic. Definitely a left and right side. However with the new adapters, the "deadish" spot front an center seems to have gone away, or is at least Far less noticeable than before I got the adapters at Redco. I even hooked up the xlr cable without adapter, and there was that dead spot!

As far as settings on the FP3, when using the adapter that plugs into input 1 and 2, both pan settings set to center. And the gain (volume) knobs for both channels at 8. Batteries read well into test "good" area of VU. I may try a different AA battery in the mike itself to see if that raises level a bit. Interestingly enough, even though the meters read -10 or so, sound good through headphones with the headphone volume set to about 7
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Old January 13th, 2013, 04:30 PM   #26
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Re: Using a stereo mic- are they your choice as a sound pro?

'both panned centre' ...... what ? You have just made a stereo mic MONO.

The left output of the mic going to ch1 should be panned LEFT and right output of the mic ch2 should be panned to RIGHT.
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Old January 13th, 2013, 04:49 PM   #27
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Re: Using a stereo mic- are they your choice as a sound pro?

Quote:
Originally Posted by Jonathan Levin View Post
with the new adapters, the "deadish" spot front an center seems to have gone away
I am afraid we are not getting through to you. "Front and center" is NOT ON AXIS FOR EITHER CHANNEL!

I have to go back and ask what you are trying to record. If you are trying to record a symphony orchestra or a choir or a string quartet, or the sound effects down at the beach, etc, then a stereo mic is marvelous. But if you are recording someone speaking, then a stereo microphone is NOT the right choice.

Now you can make it work by picking one channel (left OR right) and aim that channel of the microphone at the talker's mouth and use just that side of the microphone. Certainly it is going to look "goofy" to have the microphone seemingly aimed at one of the talker's ears. But the microphone capsule INSIDE the microphone will be properly aimed directly at the talker.

But you keep combining two different microphones that are aimed AWAY from the talker's mouth. That certainly accounts for some of the drop in level that you are experiencing.

Please UNPLUG one of the channels. PLEASE discover what TRUE ON-AXIS means for your favorite channel and do the same experiments as a MONAURAL MICROPHONE.
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Old January 13th, 2013, 06:52 PM   #28
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Re: Using a stereo mic- are they your choice as a sound pro?

Brian,

That makes sense. Thanks for that. I'm getting it.

Richard, this mike will be used for ambience, maybe group of musicians and so on.

I really do get it about the purpose of this mic, and learning to get the most out of it.

Most of my sound work will be sit down interview so for me a good wired lab is in my future (mono of coarse), as well as a hyper or super cardiod short shot gun of some kind.

I believe this will set me up for some decent audio.

Obviously the stereo mic is not ideal for most of what I do, and I appreciate the help in just getting it set up correctly with the right cables settings and so on. I'll play around with the pan per Brian and your suggestion. I'm guessing with one channell panned hard left and the other panned right my little front on dead spot will reappear. And I understand that the mic is meant to be off access to talent I.e if I had two singers one would be just to the left of center of mic and the second singer to just right of center on mic. This would then render a stereo 2 channel recording. Hopefully I got it.

Thanks Brian and Richard!

Jonathan
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Old January 13th, 2013, 10:02 PM   #29
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Re: Using a stereo mic- are they your choice as a sound pro?

Quote:
Originally Posted by Jonathan Levin
I'm guessing with one channell panned hard left and the other panned right my little front on dead spot will reappear.
No. With the left channel panned hard left, and the right channel panned hard right, IF the talent is located on the axis of the mic body, you will hear him equally on both channels, and it will sound almost like mono. There will be no dead spot.

You got the dead spot because the two channels were originally out of phase, so they were cancelling each other. Now that you have the correct cables, and the two channels are correctly in phase, you will hear a correct stereo image.

But that's still not what you want for dialog (i.e. a single person's voice). Because with the mic panned to stereo, you will get stereo background noise, air handler rumble, etc.; besides, the voice will never be perfectly centered. For dialog, you want to pan both mic channels dead center; that will give you a mono signal. And you keep that perfectly centered for your final mix, even if the fx and music are stereo.

It seems you aren't grasping this yet. I suggest you carefully re-read the above posts, especially #6, #15, and #17. If it still doesn't "click" then ask more questions. You really need to understand this basic concept if you intend to do sound work.

Last edited by Greg Miller; January 14th, 2013 at 07:44 AM.
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Old January 14th, 2013, 10:33 AM   #30
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Re: Using a stereo mic- are they your choice as a sound pro?

Greg,

You are absolutely right! Upon further testing with the pan controls in various position, things sound really quite nice. I'm finally getting a feeling for this stereo beast. Thank you so much.

I thank everyone for tearing their hair out for me on this.

Keep in mind that this whole thread started with me having a problem that I didn't even know I had: not having the proper connector (wiring) and being "out of phase". Both then new to me.

Before I go on to my next point, I want to let you know that I realize that the right equipment for the right job is what I'd adhere to. I (now) wouldn't use this stereo mic for a sit down one on one interview anymore than I'd use a 4x5 view camera to shot action shots at a football game. A lav for that, or properly placed/boomed cardiod mic.

HOWEVER: I was thinking that in a pinch, one could use the AT 822 Stereo for an interview if you had two people placed at the correct L/R angles to the mic. One person feeding mostly into chan 1 and the other mostly into chan 2, setting the pan appropriately of coarse, also allowing for some leeway in post.

Or I'll go out on a limb further and say (with a question mark) that if you were recording sound at a table where two three people were sitting across from one another (6 people total) you'd have 3 people on one channel and 3 people on the other. OR setting the pan to dead center and getting both sides but in MONO. I also bought a mono adapter from Redco that I'm now wondering if I'll need other than to free up an input on the mixer, which I suppose is possible.

Again, doing the above if you were in a bind and didn't have two separate (mono) mice pointing at opposing sides of the table. I also understand that with the separate mic situation, you have more flexibilty for positioning.

Thanks.

Jonathan
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