Topic: Mono Mic Advice

[obsidian]

I sent the below question to Gutbucket, as I really value his knowledge.  So I thought in addition to his comments I would get some thoughts on this from the whole community.

I've been thinking of using a mono mic (Countryman or similar) and using a stereo preamp.  My plan was to dial the left knob on the preamp slightly to the left, and the right knob slightly to the right ... would this make a "simulated stereo" signal going into the PCM-M10? The reason I ask is that I mount the current mics I have so close to each other that I doubt I am getting much stereo separation as it is.  I am curious to read the comments.

Not to sound corny, but please explain your thoughts as this topic is something I really want to learn from.

Thanks for the time and knowledge.

[admkrk]

All mics are mono, unless, of course, you have a stereo mic with two capsules mounted in the same body. Most preamps will have at least two channels . I am not familiar with the PCM-M10, but it looks like it only has mini (3.5) inputs. I have always run PP mics, so what I say might not be accurate.

The gain knobs on a preamp should all work in the same direction. In other words, if you turn one down and the other up, it would be the same as turning the "balance" knob on a stereo which will only make one channel louder than the other.

The distance between capsules is only relevant if you have omni mics. Several directional mic patterns rely on the capsules being close together.

It can be possible to "simulate" stereo, in a mono recording, by offsetting the left and right channels by a few milliseconds (20, for example).

[obsidian]

i feel like a newbie now ... i don't know what I was thinking about with the "slight left and right" thought process.  thanks for the great comments.

[Gutbucket]

I'll respond here, for anyone else following the discussion-

I've been thinking of using a mono mic (Countryman or similar) and using a stereo preamp.  My plan was to dial the left knob on the preamp slightly to the left, and the right knob slightly to the right ... would this make a "simulated stereo" signal going into the PCM-M10? The reason I ask is that I mount the current mics I have so close to each other that I doubt I am getting much stereo separation as it is.

You can do that (I'll discuss a couple technical details on that and make a couple comments on Admiral Kirk's post following), but you would end up with the same mono signal in both stereo channels,  call that "dual-mono' if you like.  The result would be the same as recording one mic only into one channel of the M-10 and simply recording silence in the other channel, then splitting the resulting WAV file into two mono files, discarding the silent one, and making a new stereo WAV file from two duplicates of the mono WAV that has the the recorded sound in it. Or the same as routing any single recorded channel to a stereo output bus in a mixer or stereo editing software, and panning the input to center. 

The result is still mono either way.  Nothing wrong with mono, but it's not stereo if that's what you want.  You can do some kinds of post processing to turn that into pseudo stereo afterwards, but I don't find that works very well and often prefer straight mono on it's own.

However, there are ways to get more stereo information from two microphones which are otherwise mounted too close together based on changing the way they are setup, and also by some simple manipulation afterwards.  The most appropriate option will probably be using your current mics in a slightly different way, and maybe doing some simple stuff on the computer after.  Let's explore that avenue.

What kind of microphones are you using now and how are you mounting them? 

[Gutbucket]

Technically to do what you first asked (realizing that you are simply recording two channels of the same mono information, not stereo) you'd need to split the signal before it reaches the preamp.  Then changing the relative gain through the two channels of the preamp results in panning that mono signal to a position somewhere between Left and Right, same as playing back a monophonic recording and using the balance knob on your stereo to move the mono image left or right.  It's still mono, just panned one way or the other to varying degrees.

If your goal were to use one microphone to record the same mono information on both channels of the stereo file (at the same level, thus panned "center") it would be better to use just one channel of the preamp and split the signal after leaving the preamp to feed both channels of the recorder.  Or if the M-10 has a mono file recording feature, just use that and avoid the need for doing any signal splitting with Y-cables.  I don't use an M-10 so I'm not aware if it offers that function, but some recorders do.

The distance between capsules is only relevant if you have omni mics. Several directional mic patterns rely on the capsules being close together.

This is incorrect and misleading.

Distance between the two microphone capsules of a stereo pair is always relevant, regardless of the pickup pattern of the mics used.  It is true in general that one can use less spacing between directional microphones than is commonly needed between omnidirectional microphones, but it depends on the stereo configuration, and there are exceptions (both ways)!  Yes, one can use directional mics with no spacing between them if they are directional enough and angled sufficiently away from each other.  But one can also place omnidirectional microphones very close to each other if using something between them which acts as a baffle, which blocks some sound from arriving from the opposite side to each mic - the microphones could mounted on the opposite sides of a piece of cardboard or something, with essentially no spacing between them.  Even mounting the omnis with minimal spacing and nothing between them, but simply pointing the omnis in opposing directions will provide at least more sense of stereo than using a single microphone and recording in mono.  It won't be great, big, open, lush stereo, but it will have more stereo qualities than a mono recording, and won't have mono>pseudo-stereo problems.

As Kirk mentions, one method for making pseudo-stereo from a mono recording is by introducing some delay between the two channels.  There are also other methods.  Sometimes something like that can be useful.  But as mentioned, I'd not do that as standard operating procedure. I think we can figure ways of modifying your existing microphone configuration to improve the stereo quality of your recordings without having to introduce more spacing between the microphones, and I expect that will be the better option.

[admkrk]

This is incorrect and misleading.

How about over simplified and not worded well? Since he did not say what mics he was using, I just made a blanket statement to point out that spacing the mics farther apart does not necessarily mean more of a stereo image.

[Gutbucket]

Nah.. and that's also incorrect.  Here, I'll break it down..

The distance between capsules is only relevant if you have omni mics.

^
This is totally incorrect and very misleading.  (is that better?  )  The distance between capsules matters very much when using microphones of any polar pattern.  Spacing is the most basic variable in any stereo recording microphone microphone technique.  It's simply that when using omnis in a typical spaced pair arrangement, that's pretty much the only variable we have control over with regards to the stereo configuration.  With directional mics the amount of spacing or lack of it between microphones is equally important, yet now there are also two other variables in play- the specific pickup patterns, and the angle between the microphones.

Several directional mic patterns rely on the capsules being close together.

^
This is not worded well.  Directional mic patterns are attributes of individual microphones, unaffected in most cases by how they are used in pairs for stereo recording.  A more properly worded statement would be "Stereo microphone configurations using directional mics often use little or no spacing at all between the microphones."  Since certain combinations of pickup pattern and angle between microphones correspond with using minimal or no spacing between them.

Spacing the mics farther apart does not necessarily mean more of a stereo image.

^
This is incorrect and misleading and poorly worded.  It certainly affects the stereo image, dramatically (the incorrect part).  I'm not sure what "more of an image" means though (the poorly worded part). Spacing is one of the three primary factors which come to play in determining the stereo imaging qualities achieved by a stereo pair of microphones, and the most basic and important one.  It is the only factor of major consequence when using omnis (outside of special application tricks like using a baffle as I mentioned above), and of equal importance to the shape of the pickup pattern in combination with the angle between microphones when using directional mics.

Just keeping it real.  No offence meant.  Love ya brother. 

[admkrk]

No offense taken.

I tend to say things using the fewest words possible, without over thinking anything (or thinking at all). Let me try again.

A larger distance between capsules is usually desirable with omni mics, while directional mics often rely on them being closer together. I did not include angle as I was only referring to:

...I mount the current mics I have so close to each other that I doubt I am getting much stereo separation...

 
I am not disagreeing with any of the points you made about microphones, just the way I deliver a message, and I do agree on most of those points as well. You always give a very detailed explanation, while I give a very abridged version that usually is only applicable a single situation. I do not have the patience to cover even the most common variables.

fwiw, I do not consider using a baffle as having the mics closely spaced, or even spaced at a distance. To me, that is more like running ambient and SBD, as they are physically separated.

I also have a prediction. I see you doing this after reading this: 

[Gutbucket]

 

Putting directional mics close together only works well when they are angled apart enough from each other, which how they are usually setup.  But if they aren't angled apart very much, they need to be placed further apart.  And if both directional mics are pointing directly ahead, parallel to each other, they'll need the same spacing that omnis would.


We haven't heard back from obsidian, but I'll jump to what my suggestions will most likely initially be: 

On the microphone configuration end of things, if the mics cannot be mounted any further apart, I'd suggest angling the mics further apart from each other if using directional mics like cardioids, or putting a baffle of some sort between them if they are omnidirectionals.  A baffle can be anything that blocks sound from reaching the other side- his head, his body, a piece of cardboard, a Jecklin-disk a chair back, or whatever.

fwiw, I do not consider using a baffle as having the mics closely spaced, or even spaced at a distance. To me, that is more like running ambient and SBD, as they are physically separated.

Well you should. Consider this- what a baffle does is make an omnidirectional mic directional at high frequencies.  The size of the baffle and the distance of the microphones from the baffle, affect the degree of directionality, the shape of that directionality, and the frequency at which that directionality becomes effective.  As far as high frequencies are concerned, the mics are physically separated, but at low frequencies they are not physically separated.  The low frequencies don't "see" the baffle at all, they go right around it as if it were invisible or not there at all.

Spacing between microphones matters when using a baffle just as it does any other time.  In fact, in some ways getting the spacing right matters even more.   Moke makes some classical recordings using a tiny square baffle with his miniature DPAs mounted almost right up against either side, very little spacing between the microphones and between the microphones and baffle.  It's very small and very compact.  And that might something obsidian can try.  At the opposite extreme, Ray Kimbers gigantic ISOphone system (I think that's what it's called) uses a giant baffle that needs a crane to lift it, and uses a mic spacing of something like 8-10' or more.   Over the course of his career, Jorg Jecklin- the guy the Jecklin Disk is named for, revised the dimensions of his baffle slightly and the suggested mic spacing majorly, all because spacing matters.

I did a series of experiments up at Live Oak 10 years ago, trying all kinds of different mic spacings while using the same baffle, from the same spot in the amphitheater.  Each spacing sounded considerably different.  As a way of reducing the very wide spacing I wanted to use for the omnis, I at one point I considered making two tiny baffles, one for each mic, and placing each relatively close to it's own baffle, then spacing the baffles apart on a mic bar.

Spacing matters with a baffle.  Spacing always matters. 

I've another suggestion for something to try afterwards on the computer, which can help somewhat when an insufficient amount of spacing and/or angle has been used.

[admkrk]

You still seem to miss that I purposely left out angles, and only responded to spacing. In the context I was using angles were not a factor.

I am curios how the two baffle deal worked out, if you tried it. For most situations, I would visualize a baffled pair as two lavaliere mics, back to back. Low frequencies do have a tendency to go everywhere and through everything, and as a former bass player, I know this well. The baffle blocks the reflections from one side reaching the other, or at least at the same time, which accounts for the separation. Of course spacing still matters, because the reflections on the baffled side will change accordingly, also.

[Gutbucket]

Never did the flat mini-baffles (was thinking of something about the size of a CD case, maybe using the clear plastic disc that came atop a spindle of CDRs). Conceptually it would have worked and offer lots of tunability- not only adjustable spacing between the baffles but also  the ability to angle each baffle independently of the other, so they could be angled forwards facing 90 degrees apart or whatever, similar to pointing a pair of cardioids. 

Instead, I started flush mounting the omni lavs in dense hard foam balls, which act similarly by making the omnis slightly directional at high frequencies while also providing a presence lift, with a smoother off-axis curve around the ball, while being smaller, less visually intrusive and easier to manage and fly on the telescopic TV antennas.  Also worked to as a safety against eye-pokeage, as I often use this way FOB or at the stage-lip.  So using the balls turned out to be advantageous in lots of ways, but the original intention was figuring out a way to use the omnis with less spacing between them.  I don't use the balls on the rig you saw me running last year at Wanee, because there I extend the omnis out further to 5' or 6', about twice as far apart as in these photos.

Some photos of the small ball-mounted omnis at a Bear Creek Fest up at Live Oak. You may be familiar with these from the Oddball Mic Techniques thread.  You'll see 4 balls on stalks in these photos, since I was running 4 omnis in a diamond pattern sort of a Decca-Tree thing for surround playback, but it works the same with a typical single pair.  There are windscreens on the balls in the last photo with Robert Walter on the organ in the background-

[admkrk]

That is an interesting approach. It reminds me of mounting omnis in a "dummy head". I would imagine that a pair, spaced right and angled slightly forward from 180 degrees, would give a similar result.

[obsidian]

I get a sick thrill out of reading all this stuff.  It's amazing the amount of knowledge that is freely available on this site.

I apologize for not giving more information, as I have sold my previous setup (a set of AT853 which I clipped under collar) and was asking about the mono mic as an option while doing some basic research for a new setup.