Topic: What you can achieve with just 2 mics

[voltronic]

This is one of the more impressive recordings I've heard using just one pair of mics, and easily THE best M/S recording I've heard.

https://www.gearslutz.com/board/remote-possibilities-acoustic-music-location-recording/1023984-mahler-3-two-mikes.html

Having 2 MKH 30 > Nagra VI certainly helps, but clearly technique is the deciding factor as always.

[rocksuitcase]

voltronic,
kindms and I have been doing MS with his AKG 414 XLIIs' since last summer. Usually for large outdoor Rock/jamband shows with huge sound systems, but recently did one indoors at the Capital Theater.
 With gutbuckets guidance, and encouragement we have created a good method for clipping/mounting. None of them are on the LMA but if you are interested, I can set up a location for you to DL from.

my basic analysis is similar to yours; when compared to 2 cards or 2 supercards the depth and realism is quite astounding.

[2manyrocks]

The gentleman who made that recording has decades of experience and is often quick to recommend using quality mics and recorders.  His continual good recordings using two mics captured my own attention as it bucks what seems to be the trend towards more mics and more channels.  My pocketbook would rather pay for two good channels.

[kindms]

voltronic,
kindms and I have been doing MS with his AKG 414 XLIIs' since last summer. Usually for large outdoor Rock/jamband shows with huge sound systems, but recently did one indoors at the Capital Theater.
 With gutbuckets guidance, and encouragement we have created a good method for clipping/mounting. None of them are on the LMA but if you are interested, I can set up a location for you to DL from.

my basic analysis is similar to yours; when compared to 2 cards or 2 supercards the depth and realism is quite astounding.

correction

AKG414XLS not XLII's.

And I thought some of the m/s stuff made it to the LAM no ? Anyway the ARU sounds pretty good. We went Mid = subcard and side = fig8. The room definitely is front and center. I think if i was going to run again from that spot probably would go straigh card for the mid or a SD card. that might help the "attack" but overall happy with it

[rocksuitcase]

voltronic,
kindms and I have been doing MS with his AKG 414 XLIIs' since last summer. Usually for large outdoor Rock/jamband shows with huge sound systems, but recently did one indoors at the Capital Theater.
 With gutbuckets guidance, and encouragement we have created a good method for clipping/mounting. None of them are on the LMA but if you are interested, I can set up a location for you to DL from.

my basic analysis is similar to yours; when compared to 2 cards or 2 supercards the depth and realism is quite astounding.

correction

AKG414XLS not XLII's.

And I thought some of the m/s stuff made it to the LAM no ? Anyway the ARU sounds pretty good. We went Mid = subcard and side = fig8. The room definitely is front and center. I think if i was going to run again from that spot probably would go straigh card for the mid or a SD card. that might help the "attack" but overall happy with it

Good correction on the mics. I am not sure what is on the LMA from our SAT 08-01-14 mainstage MS run. If voltronic wants we can find some for him. But i suspect that rock n roll is not what he is interested in.
 

[kindms]

interesting. the linked thread says he did M/S with 2 figure 8 mics.

I have never thought of running this way. typically i would just go blumlien. might have to try it out one of these days

[voltronic]

I'll repeat some of the comments I posted to that GS thread.  I've never been happy with my own recordings made with the MK4/MK8 combo I borrow.  I get either to much mid/mono, or too much swimmy ambiance depending on how live the hall is.  Part of that is probably due to my limitations on placement forcing me too far away, outside the critical distance for M/S, or maybe my lack of technique and experience.

For the recording linked in that thread, Rolo is using Blumlein M/S, which uses a pair of fig-8s like regular Blumlein, but rotated to be set up like a "regular" M/S array that uses a center cardioid.  There's some debate in the thread on whether or not those mics need to be a matched pair, as you would in Blumlein.  To my ears, this recording has the satisfying sense of space like you would get with spaced omnis.  I suspect that this may be due in part to using the pair of fig-8s.

FWIW, I've never really enjoyed the sound of Blumlein (as opposed to M/S Blumlein), especially with classical.  It always sounds thin and congested to me.

[Gutbucket]

M/S with two 8's is the way Blumlein did Blumlein!

There are some advantages to doing it that way:

With the 414's M/S provides the easy-option to quickly change the mid pattern to something more forward biased if necessary (or just to try something different sets to set or whatever).   The 414 has what, 5 patterns to choose from total, maybe 7?  That provides at least one, and maybe two super/hyper-ish patterns between cardioid and fig-8.  And those are the Mid patterns I'd be interested in for a config which has more Blumlein-ish qualities than M/S using a cardioid Mid, yet is likely to work better in most situations than traditional crossed 8's, due to the forward Mid bias.  It will also have a bit more bottom octave bass extension.

If the mics are not closely matched, M/S 8's will be more robust than L/R crossed 8's.  Any differences will manifest across the resulting stereo image symmetrically, between the center and both sides, rather than asymmetrically with one side different from the other.

There is a thread I started here years ago about why hall ambience recorded with Blumlein sounds more like spaced omnis than other coincident or near-spaced configs.  If I can find it I'll like it here.

[voltronic]

M/S with two 8's is the way Blumlein did Blumlein!

There are some advantages to doing it that way:

With the 414's M/S provides the easy-option to quickly change the mid pattern to something more forward biased if necessary (or just to try something different sets to set or whatever).   The 414 has what, 5 patterns to choose from total, maybe 7?  That provides at least one, and maybe two super/hyper-ish patterns between cardioid and fig-8.  And those are the Mid patterns I'd be interested in for a config which has more Blumlein-ish qualities than M/S using a cardioid Mid, yet is likely to work better in most situations than traditional crossed 8's, due to the forward Mid bias.  It will also have a bit more bottom octave bass extension.

If the mics are not closely matched, M/S 8's will be more robust than L/R crossed 8's.  Any differences will manifest across the resulting stereo image symmetrically, between the center and both sides, rather than asymmetrically with one side different from the other.

There is a thread I started here years ago about why hall ambience recorded with Blumlein sounds more like spaced omnis than other coincident or near-spaced configs.  If I can find it I'll like it here.

Everything I've ever read indicates that Blumlein had his array such that the the sound source is 45deg off axis.  There is very little I can find about doing M/S Blumlein, and all of it relatively recent.  Can you point me to anything that says otherwise?  It's the array where the center of the source is off axis that I don't enjoy as much, and I wonder if the phase cancellations have anything to do with it.

http://www.emusician.com/how-to/1334/blumlein-pair-stereo-miking/38232

EDIT: It actually turns out that Blumlein had both arrangements on his original patent.  See page 37, left column:
http://decoy.iki.fi/dsound/ambisonic/motherlode/source/British%20patent%20specification%20394325%20Blumlein%201933.pdf

[Gutbucket]

Yes, from Blumlein's original patent (thanks for linking it above, it is interesting and recommended reading for recording geeks) and from his biography I read a number of years back.  The biography is rather dry and not particularly well written, but quite thorough in detailing his research and patents up to his tragic death developing airborne radar during WWII. 

Here's the thread I mentioned above: Why Blumlein sounds more spacious than other coincident or near-so arrays- http://taperssection.com/index.php?topic=110861.msg1480342#msg1480342

[Gutbucket]

It's the array where the center of the source is off axis that I don't enjoy as much, and I wonder if the phase cancellations have anything to do with it.

I've found that I often prefer to err on the side of a bit less angle than 90 degrees between microphones for Blumlein.  It solidifies the middle nicely.  Easy to do that by adjusting the mix ratio from a Blumlein pair setup as M/S since one needs to decode it to L/R anyway,  but the same can be done with an X/Y Blumlein pair by matrixing over to M/S, adjusting ratio and matrixing back to L/R again.  Maybe that's what you are hearing?

Not sure what phase cancellations you are referring to.  Ideally setup with the mics fully coincident, there won't be any phase differences between the two microphone signals, only full polarity inversions.  If not setup sufficiently coincident, the incident angles of maximum summing error will be from 45,135,225 and 315 degrees off-axis for a M/S Blumlein pair, and 0/90/180/270 degrees for a 90 degree X/Y Blumlein pair.

[voltronic]

I'm taking about the rear lobes of the X/Y fig-8 picking up the signal from the other side in inverted phase.  DPA says it better:

http://www.dpamicrophones.com/en/Mic-University/Stereo-Techniques/Blumlein-Stereo.aspx

Taking an X-Y Blumlein and running it through M-S processing is an interesting idea.

If you go back to the GS thread I linked, you'll see that I'm involved in a bit of back and forth with a couple members who are saying these two Blumlein variations are identical mathematically and in sound.  While that may be true at the time of capture, and if the gain levels are the same, I don't see how that is still true after processing the mid mic of M-S in your decoding matrix, especially since you'll likely adjust its level, making the interaction between your pair of mics different than it would be in the X-Y type of arrangement.  I was wondering if you or DSatz could weigh in on that - the people over there don't seem too interested in the post-processed M-S aspect of what I'm talking about, or I have a serious misunderstanding somewhere.  It wouldn't be the first time.

[Gutbucket]

They are identical mathematically.   They'll vary slightly in actual implementation due to the inability to mount them so they are truly coincident, and also due to the pattern-response variations in real-world microphones.  But those differences should be minor if done properly.

Let's assume a pair of well behaved 8's, mounted so they are as coincident as possible.  The direct L/R output of those microphones when arranged in a 90 degree X/Y configuration will be very, very close to the matrix decoded L/R output of the same microphones if arranged Mid/Side, and decoded with a 50:50 ratio.  Changing the ratio of that M/S decode is doing exactly same thing as changing the physical angle of the X/Y pair.  Using all Mid signal matrixed with zero contribution from the Side signal (100:0 ratio) is the same as angling both X/Y 8's so they both point directly ahead.  As far as the output signal is concerned, both situations are equivalent to a single forward facing figure 8 mic.

Likewise, using all Side signal with no Mid in the M/S matrix (0:100 ratio) is doing exactly the same thing as pointing the X/Y pair 180 degrees apart, with both mics facing directly to the sides.

Note: The behaviour described above only applies to two figure 8's. When the Mid/Side ratio is adjusted using any other Mid pattern than fig-8, not only will the angle between virtual microphones change, but the virtual polar pattern will also change, simultaneously.  Crossed 8's are unique with regards to two channel M/S matrixing due to their front/back pattern symmetry.  Their virtual patterns always remain 8's regardless of the Matrix ratio.

The L/R output from either a 90-degree X/Y or the equivalent 50:50 Mid/Side ratio will be a signal with the same (positive) polarity in both channels for all sounds arriving at the microphones from the quadrant in front.  Sounds arriving from the rear quadrant will also produce signals with the same polarity in both channels, but polarity of those signals will be inverted (negative) relative to sounds arriving from the front.  Sounds arriving from the side quadrants will produce signals with positive polarity in one channel and negative polarity in the other.  No phase differences between the signals in the L/R channels will occur, regardless of angle of arrival.

Extra credit question: How are sounds handled which arrive from directly above and below a Blumlein pair of 8's when in X/Y? ..and when in M/S?
Lab credit: Take an Blumlein X/Y recording and run it through a L/R>M/S>L/R matrix and play around with the matrixing ratio.  Can you get it to sound similar to the Blumlein M/S recordings you've expressed a preference for?  The Voxengo MSED plugin (its free- http://www.voxengo.com/product/msed/) is an good way to do that.  It only does M/S matrixing so isn't overly complicated.  Leave the pan controls centered and use it's "Inline" mode to do the L/R>M/S>L/R adjustment thing, which is two matrixing operations with your matrix ratio adjustment being done between them.

[mfrench]

I got tired of rolled off bass with figure-8.
So,... use a center cardioid!?!
That would be the other steeply rolled off bass pattern.

Now, maybe with a wide/sub-card. But, the rolled-off bass thing always bugged me.

[voltronic]

^ ^

Thanks, now I get it.