Parallel spaced mics on a single instrument

[fred_ersd]

Hi to all.

A technical question for the microphone tecniques dept.

I have seen in various pictures of recordings of classical music that single instruments (cello, wind and string instruments) are close miked with two paralell spaced microphones.
To me this does not sound very appropriate in theory due to possible phase problems.
Can anyone explain on this? Maybe only ONE close mic is used in the mix?
Cardio or omni?

Thanks.

Some examples:
On cello:
David Finckel and the Taipei Symphony Orchestra | Flickr - Photo Sharing!
Teorbo, drums, singer, recorder from the recording of spanish recorder player Vicente Parrilla's most recent CD

[king2070lplaya]

I've found that when you use just 1 spot mic in combination with room mics, especially on vocals, and you mix in the spot, it doesn't sound natural, but rather like it's pasted on there as in a pop mix. So I use 2 mics close together, facing the same direction, and pan them left and right and it yields a bit more natural sound. As long as the source doesn't move much or is placed back a bit on one who does (ie an impassioned singer) the source stays centered. I don't exactly understand why it works, maybe someone else can explain this a bit, but it works like magic.

I use figure 8's for this, but have used and observed cards and hypocards being used as well, so it should be flexible in terms of pattern

This is very common on classical vocalists:

http://www.youtube.com/watch?v=_IlGjXhVwVQ

[pkautzsch]

This is "standard" stereo miking of classical instruments. You want to give each instrument a sense of space, and that's what you get with a closely spaced pair. As the spacing is small, often about 6", the instrument will be quite stable in the stereo image, but not "pinpointed" (like in a jazz or pop mix).
Usually there is a main pair or at least a "room pair" as well.
If a singer moves a lot L/R, one might set the close pair up vertically.

[rumleymusic]

To me this does not sound very appropriate in theory due to possible phase problems.

These would normally be treated as a close stereo spot, so phase between the mics would not be an issue. I would assume omni if the mics are parallel, but cardioid can work also at this range.

[JonesH]

They really blend with the main mics much easier. Mono spots are more obvious. It can make for some trickiness with the stereo image of an ensemble though.

[Yannick]

I have to offer a dissident opinion.
I really hate this sound.

If you need a stereo spot this is the moment to use an ms. You can always make it fit to the mains, as you can change the width and rotate in post.
There really is no excuse to use any other technique.

As an example I love what DGG is doing on orchestral recordings, but Solo voices are quite awful because of this double or even triple spot technique... Comb filtering galore + unstable stereo imaging.

[king2070lplaya]

Hey Yannick,

which vocal recordings are you thinking of on DG that exhibit this comb filtering?

Also, I see where you're coming from with the MS thing, I think reason one would use parallel mics rather than MS is that, say you use MS to spot a soprano standing in the middle of an orchestra, that S channel is really only going to pick up the instruments to the left and right, rather than good usable vocal ambience. If you've had success with this technique in this situation, though, that would be awesome to hear about.

[Plush]

Stereo micing enables you to steer the soloists sound and place it in the stereo picture.
The b&w pics of the vln + lute / theorbo are proper stereo mic technique.


However, I don't think much of the mentioned picture though. (the picture with David Finckel) The mics are are too widely spaced and they are set up to CREATE a specific problem.

Who can tell me what that problem is?

[studer58]

3:1 rule violation ?

[king2070lplaya]

This technique will always defy the 3:1 rule as the mics are so close together that the player would have to be within 1-3" of them to follow it!

If you're talking about the mics on cello w/ orchestra, you're going to get some extreme width issues, i.e. hole in the middle, low end phase cancellation, etc. He'll probably bounce around a bit in the stereo image too.

[Brackish]

Originally Posted by pkautzsch

a closely spaced pair. As the spacing is small, often about 6"

What's mostly used here? Cards?

And they'd be positioned parallel [i.e. side by side]?

[David Spearritt]

Yes, cardioids. I saw some pictures from a previous EBS website that showed the two MKH800's, a little less than shoulder width, 1m away from operatic singers during recording sessions. You can clearly see the mics are set to cardioid.

I tried this myself and got ordinary results, no matter how I panned them.

Not a patch on using a blumlein mic on operatic singers, which I find to be the most stunning solo vocal mike technique of all, when you are in a concert hall standard acoustic.

[Yannick]

Originally Posted by king2070lplaya

Hey Yannick,

which vocal recordings are you thinking of on DG that exhibit this comb filtering?

Also, I see where you're coming from with the MS thing, I think reason one would use parallel mics rather than MS is that, say you use MS to spot a soprano standing in the middle of an orchestra, that S channel is really only going to pick up the instruments to the left and right, rather than good usable vocal ambience. If you've had success with this technique in this situation, though, that would be awesome to hear about.

I dont see why any other stereo technique would be able to pick up more ambience without picking up more bleed.
Thing is, with an MS you can control the bleed afterwards. stereo spotting is more about creating a believable image/width then picking up air. This being said, a figure of eight often picks up more ambience then a cardioid, because you can actually stay further from the source.

I like spotting with bidirectionals, or MS with a bidirectional M mic.
You can aim in quite a narrow plane, ie you can get the woodwins without too much brass or strings, without getting way too close.

Re the DGG recordings, I think most of the orchestral stuff with vocal soloists will apply ? There are some vids around the internet.

[JonesH]

Originally Posted by Yannick

, a figure of eight often picks up more ambience then a cardioid, because you can actually stay further from the source.

Usually a fo8 and a cardioid is described as having the same distance factor of 1,7...?

[king2070lplaya]

@Yannick

My thinking was, with the spaced-close way, you have 2 mics pointed at the same source and getting essentially the same signal, which is dominated by the voice right in front of it. When you pan them out, because of they are slightly out-of-phase relative to each other, they widen the voice in the stereo image. And while the image is still rather narrow relative to the whole field, it is wider than if you just had a single spot mic, and in a way that helps it to blend very nicely with the main stereo pairs.

With MS, you have the 2 mics creating a stereo image, but this time 1 mic is pointed at the source, and 1 places the source in the null, which at that close of range (3-5 ft) means basically none of the source will be heard in that side mic. I realize you can adjust the width of MS by turning up the sides, but in this case, because the side mic isn't picking up ANY voice, the width of the voice won't really become any wider, which seems to me the objective of the spaced technique. Also, MS lacks the out-of-phase cues that give spaced pairs (and your ears) a bit wider set in the lower frequencies.

At least that's my experience here. I haven't used an MS spot in a while though so it's due for another go. I think about how you describe an MS spot on woodwinds and it seems like a terrific idea I will have to try!

I use the spaced technique quite a bit and don't find a noticeable problem with comb filtering, probably because it is panned hard L and R, and I only ever really use it on sources that will fill the center image (so no problems having to pan-in or to a certain spot)

I actually use bidirectionals as spots quite a bit, for the reasons you mentioned.

I was going to say that Anna Netrebko's Russian album is I a great example of the spaced sets doing a terrific job capturing beautiful voice on a DG release, but when I found a video of the session she is singing into a single tlm-170. Guess i'll keep looking!

[king2070lplaya]

Here's a cool one

Project K622 Page 2 | Stereophile.com

In paragraph 14 (pg 2) Tony Faulkner explains why he uses an AKG c24 as a single spot mic.

"Using a stereo microphone like a C24 rather than a single mono mike gives me, as engineer, more flexibility in minimizing that typical pasted-on mono quality of a single spot microphone"

This whole article is pretty awesome actually, check it out

[eveaudio]

I find that if you delay the spot mics correctly, you can blend them into the stereo mix for presence - without that "pasted on" vibe.

[Audiop]

Originally Posted by JonesH

Usually a fo8 and a cardioid is described as having the same distance factor of 1,7...?

Although I lack the math skills to actually calculate it it is my understanding as well that an ideal dipol and cardioid has the same energy response.


/Peter

[Plush]

The answer to my question above is that Finckel moves a lot when he plays. That means that he is one time in the left mic and next in the right mic.

Narrowing the spacing of the spots would get rid of this tendency.

(also a way to use this is to move both mics' panning to the left. One at hard left and the other at 9 o'clock.)

Stereo micing can make the soloist's sound "hover" in the stereo picture if placed correctly--and if that's what the engineer wants.

[Marlan]

An XY is also nice technique to use in this situation. It gives a nice stereo image, can be mixed in sparingly, and is not prone to phase problems.

[Yannick]

Originally Posted by JonesH

Usually a fo8 and a cardioid is described as having the same distance factor of 1,7...?

Exact. You missed the next part where i say you can often put the fig8 further. As they have the same distance factor, the fig8 will have more ambience.

[Yannick]

Originally Posted by king2070lplaya

@Yannick
I realize you can adjust the width of MS by turning up the sides, but in this case, because the side mic isn't picking up ANY voice, the width of the voice won't really become any wider, which seems to me the objective of the spaced technique. Also, MS lacks the out-of-phase cues that give spaced pairs (and your ears) a bit wider set in the lower frequencies.

Actually i turn down the sides, not up. A soloist in the mains is not very wide, in a MS spot it would be too wide without turning down the S component.

An MS will also give out of phase cues, the bleed will mainly be out of phase, and low level so it will not interfere with the mains.
If the spot has some coherent pickup of the orchestra, yo can always adjust width and rotation accordingly.

[Yannick]

Originally Posted by Plush

The answer to my question above is that Finckel moves a lot when he plays. That means that he is one time in the left mic and next in the right mic.

Narrowing the spacing of the spots would get rid of this tendency.

(also a way to use this is to move both mics' panning to the left. One at hard left and the other at 9 o'clock.)

Stereo micing can make the soloist's sound "hover" in the stereo picture if placed correctly--and if that's what the engineer wants.

Narrowing the spacing would also worsen the comb filtering.
A narrow MS would also counteract the soloists movement, and you can even follow the anti-panning during mixdown

[JonesH]

Originally Posted by Yannick

As they have the same distance factor, the fig8 will have more ambience.

Ahhh you mean since the Fo8s are more narrow and you won't get as much bleed from sources to the sides? Yeah, then it makes sense again.

[Plush]

Originally Posted by Yannick

Narrowing the spacing would also worsen the comb filtering.
A narrow MS would also counteract the soloists movement, and you can even follow the anti-panning during mixdown

I'm just mentioning how it works in practice, not in theory.
There is no comb filtering.

MS is the wrong type of pick-up for a soloist because it extends the width of the picked up sound. That is definitely not what we want because we want to be able to pan and place the soloist pick-up into the stereo picture.

YOu never use a pick-up with exaggerated left-to-right on a stationary playa.

[Yannick]

Originally Posted by Plush

I'm just mentioning how it works in practice, not in theory.There is no comb filtering.

MS is the wrong type of pick-up for a soloist because it extends the width of the picked up sound. That is definitely not what we want because we want to be able to pan and place the soloist pick-up into the stereo picture.

There is comb filtering, as there is inter-aural crosstalk between the two speakers, unless you listen on headphones.

Strangely, my case in favour of MS is exactly that: you can narrow it, you can pan it and you can place it, even rotate it and skew it.
If you can do all that with AB setups (in post !) without additional comb filtering (which will happen if you do not pan the two mics full L and full R) then you must know some secrets.

[mpdonahue]

Yannick,
This seems to me to be a bit of a solution in search of a problem. The main reason I use a pair of closely spaced microphones as spots is to specifically get the sound of spaced microphones (usually not omni's for spot mics), much the same way I also use spaced omni array's for mains rather than coincident systems.
As to the whole comb filtering issue, I'm with Hudson. There is enough comb filtering going on between the spot and the mains that the comb filtering of the spot pair really is of no consequence. FWIW, you are getting comb filtering above 2k in the case of a 6" spaced pair.......not really a big issue. As to the IATD, this is what we are using to diffuse the sound of the spot mic in the mix and make it sound more natural. This is what allows you to use a little more of the spot pair to get a little more of the soloist when compared to a single spot mic without getting the ugly mono spot character.
Finally, the closer you space the pair of solo spots, the wider you can pan the pair, ultimately hard left and right, where comb filtering of the pair goes away completely. (to be honest, we need to remember that this is an issue of summing. If you can get away without panning the spots, there is absolutely no comb filtering.....)
As always, YMMV.

All the best,
-mark

[Brackish]

Originally Posted by Plush

You never use a pick-up with exaggerated left-to-right on a stationary playa.

So what type of stereo spot do you recommend on a soloist?

[Brackish]

Originally Posted by mpdonahue

the closer you space the pair of solo spots

So what are you using mostly? Cards in parallel at about 6" apart?

[mpdonahue]

Originally Posted by Brackish

So what are you using mostly? Cards in parallel at about 6" apart?

I typically end up anywhere from 6" to 18" depending on the source and situation. As to patterns, it really can be anything..... depends on what I'm looking for soundwise.
All the best,
-mark