Topic: Figure 8 mics

[John Willett]

Now, the biggest problem with most coincident stereo recording methods such as M/S is their lack of perceived spaciousness--a quality which depends critically on the pickup of difference information at low frequencies. So this rolloff, while it makes great sense for dialog and effects recording, is the opposite of what would normally be desired for music recording.

It's funny you mention this (and I apologize for the slight hijack).  I was just revisiting some M/S recordings I made (using and Avenson STO omni mid and an MKH30 side), wondering why they didn't sound that great to me.  I tried playing with the low freq. in the side mic and I found I liked it better rolled off a bit.  Basically, it allowed me to add more side before it sounded too phasey.  With more bass in the side mic, I had to keep it's level down a bit and the image was more narrow. 

I've heard others mention the uncorrelated low freq. being key to spacious coincident recordings, but my own experience does not match that so much.  Don't we hear lower frequencies in mono anyway?  Taking an M/S recording and lowering the bass on the side mic, then turning the side mic gain up higher gave me a much more spacious image.  Obviously, we each have our preferences.   

Sounds like you need to read up on Alan Blumlein's Shuffling technique.

[DSatz]

leddy asked: Don't we hear low frequencies in mono anyway?

No; that's a myth or at least a "mythunderstanding" (promoted unfortunately by some manufacturers of combined subwoofers). We don't localize low frequencies nearly as readily as we can localize in the upper midrange. But directional information at low frequencies (i.e. differences between/among the channels) is as vital to stereo sound reproduction as it is in other frequency ranges; it just serves a different function. At low frequencies it mainly affects the "feel" of the recording and the sense of being immersed in the space where the recording was made rather than the space that you are in when you're listening; localization isn't the point.

Of course there are different tastes and preferences--sometimes a lot different. A lot also depends on how your loudspeakers are set up and how your listening room works acoustically. The big risk when post-processing any recording is that your settings will solve the particular problems of your own playback system and environment, and then will sound odd or inappropriate when someone else listens to them somewhere else over different speakers.

[leddy]

Now, the biggest problem with most coincident stereo recording methods such as M/S is their lack of perceived spaciousness--a quality which depends critically on the pickup of difference information at low frequencies. So this rolloff, while it makes great sense for dialog and effects recording, is the opposite of what would normally be desired for music recording.

It's funny you mention this (and I apologize for the slight hijack).  I was just revisiting some M/S recordings I made (using and Avenson STO omni mid and an MKH30 side), wondering why they didn't sound that great to me.  I tried playing with the low freq. in the side mic and I found I liked it better rolled off a bit.  Basically, it allowed me to add more side before it sounded too phasey.  With more bass in the side mic, I had to keep it's level down a bit and the image was more narrow. 

I've heard others mention the uncorrelated low freq. being key to spacious coincident recordings, but my own experience does not match that so much.  Don't we hear lower frequencies in mono anyway?  Taking an M/S recording and lowering the bass on the side mic, then turning the side mic gain up higher gave me a much more spacious image.  Obviously, we each have our preferences.   

Sounds like you need to read up on Alan Blumlein's Shuffling technique.

It's my understanding that you add a low frequency boost to the side channel.  Is it more complicated than that?

Perhaps the issue is the MKH30 has more extended bass than my mid mic to begin with.  At some point, I'm sure you can have too much low frequency in the side mic.  Perhaps my mic choices are starting me at that point, now that I think of it.  Anyway, I don't want to hijack anymore than I have. 

Thanks.


 

[Gutbucket]

..A lot also depends on how your loudspeakers are set up and how your listening room works acoustically. The big risk when post-processing any recording is that your settings will solve the particular problems of your own playback system and environment, and then will sound odd or inappropriate when someone else listens to them somewhere else over different speakers.

+10

[DSatz]

leddy, I for one don't find this very much of a hijack, since it's directly relevant to the way that figure-8 microphones are used most often.

Blumlein's "shuffler" circuit was actually a way to increase the low-frequency difference energy between a pair of closely-spaced omnidirectional microphones. His famous patent discusses the technique of crossed figure-8s that later became associated with his name, but it was a theoretical discussion, since at the time, he only had access to EMI microphones and they didn't make a high-quality figure-8. His famous early stereo recordings were made with near-coincident omnis plus this "shuffler" circuit. So the shuffler isn't strictly relevant here, except as testimony to the great importance of picking up difference energy at low frequencies.

--best regards

[Tom McCreadie]

Blumlein's "shuffler" circuit was actually a way to increase the low-frequency difference energy between a pair of closely-spaced omnidirectional microphones.....

Yes, Blumlein's shuffling technique in his paper could actually be considered as his workaround to derive a Fig-8 mic - which, as you mention, didn't exist as commercial mics at that time - using the mics that he did have at his disposal, viz. omni's. Nowadays the meaning of shuffling has morphed and also diverged a bit. When applied to coincident mics, it is often a gentle bass boost of ca. 1-2dB somewhere between 250 and 650Hz, But it is a far more complicated than that.

By by far the most erudite and thorough treatment of the topic Shuffling has been by Michael Gerzon, and I strongly urge you to get your hands on the following two literature articles:

- "Application of Blumlein Shuffling to Stereo Microphone Techniques", M.A.Gerzon, J. Audio Eng.Soc. Vol 42, no. 6 (1994), p435-453
- "Stereo Shuffling:  New Appproach - Old Technique", M.A. Gerzon, Studio Sound (UK), July 1986, p122-130

Remarkable person was Gerzon. Like many audio giants, he too died far too young. Besides doing the theoretical spadework for the Soundfield mic, he was also ,as I understand, involved in developing the Waves plugin stereo imager modules (which do contain a shuffler).

[notlance]

"By by far the most erudite and thorough treatment of the topic Shuffling has been by Michael Gerzon, and I strongly urge you to get your hands on the following two literature articles:

- "Application of Blumlein Shuffling to Stereo Microphone Techniques", M.A.Gerzon, J. Audio Eng.Soc. Vol 42, no. 6 (1994), p435-453
- "Stereo Shuffling:  New Appproach - Old Technique", M.A. Gerzon, Studio Sound (UK), July 1986, p122-130"

The second article from Studio Sound is available online here:

http://www.audiosignal.co.uk/Resources/Stereo_shuffling_A4.pdf

"Remarkable person was Gerzon. Like many audio giants, he too died far too young. Besides doing the theoretical spadework for the Soundfield mic, he was also ,as I understand, involved in developing the Waves plugin stereo imager modules (which do contain a shuffler)."

There is a thread here about Mr. Gerzon:

http://taperssection.com/index.php?topic=130689.0

[DCaswellUK]

Hi everybody,
I'm a bit confused by the positioning of the schoeps mk8 in a mid side array..in the picture on the Schoeps page the mk8 is placed 'lying down' alongside the other mic, so that is clear, but could someone help me by explaning the setup for mid side using two schoeps mk8s. Are they both placed horizontally (as the mk8 is when used in conjunction say with the mk4) Are the caps then arranged so the mid mic fig 8 shows 8 while the other is rotated sideways??
Or is the mid mic fig 8 needing to be vertical.
In xy blumlein, can the fig 8s just be crossed as if they were cardioids, or do the caps need to be facing at one another and then the angle created by rotating them?
I'd be very grateful if someone could explain it!
Many thanks,
David Caswell
 

[SmokinJoe]

David, I don't have explicit experience with Schoeps, but I think it's a generic question.

In theory, whether the SIDE mic is horizontal or vertical shouldn't matter, as long is it's sides are pointing Left/Right. Most people think of using a card/subcard/hypercard for MID and with an end-address mic, the "horizontal pair" configuration makes sense in regards to mounting.  I saw someone do that with an AT-4050 side/Octava MC012 card mid (I don't know how it sounded, but it caught my eye when I saw it).

With 2 side address mics like my AKG414's, they are generally stacked vertically, probably because it's just easier to mount 2 mics that way, and tradition.

If you want to use a Figure8 for the mid, basically you set it up like blumlein, and rotate the whole assembly 45 degrees so it's point MID=front/back, and SIDE=Left/right.  The idea of "vertical stacking" comes to mind similar to the 414's, but you could have them both horizontal at 90 degrees, much like SD cards are set up for XY.  One possible advantage to vertical stacking is that with the horizontal XY approach you would have the other mic's body partially obstructing one of you Fig-8 lobes, which may (or may not) effect the resulting sound.

[boojum]

I use the Schoeps CMC64 + CMC68 for MS and use the CMC68 horizontally on the bottom with the CMC64 above and parallel to the CMC68.  I usually use a KC5 cable and the $20 Schoeps plastic connector to attach the CMC64 to the top of the CMC68.  The sound and imaging are excellent and the two combined present a very small package to interfere with sight lines.

I really like this setup as it is small, unobtrusive, easily set up and allows some tweaking in post.  Despite some folks dismissive comments about MS I find it works very well.

[DSatz]

Hello, my fellow David (Caswell). The picture on the Schoeps site (actually I don't know which picture you mean, but your description of it is clear enough) is appropriate for mid/side recording where the M microphone is "forward facing" or "end-addressed" or "axially addressed" or "end-on" or such terms. That type of arrangement wouldn't work if the M microphone is a figure-8, which is "side-facing" or "side-addressed" or "radially addressed," etc.

For M/S recording with two figure-8s two arrangements are possible, with a variety of options in between if for some reason that suits you better. Arrangement #1 would be with the capsules placed "head to head" vertically. The 0° axis of whichever mike you designate to be S will be facing to the left of the direct sound sources, while the 0° axis of the M microphone will face straight forward toward the center of the sound sources. In other words, it's simply a traditional Blumlein array rotated 45°.

But since the figure-8 pattern is three-dimensional, the S microphone could, if you like, be mounted horizontally as long as its 0° axis still is aiming to the left (as in the Schoeps picture). Or if the mood strikes you, you could tilt the "S" microphone at any other angle you like between the horizontal and the vertical.

The corresponding "twist" for the M microphone would be to install it "non-vertically," but that would invariably create a left-right asymmetry that is exactly what to avoid in such setups.

--best regards

[DCaswellUK]

Many thanks for the help and advice. In particular to David Satz.. I have read many of the threads about ms in which you have contributed, and am really grateful for the insight into this technique that your observations have given me..I've had a lot of fun renting different caps for my cmc6s to experiment with all the different combinations possible..The mk8 pair 'blumside' will be the next to try!
Thanks again,
Kind regards,
David Caswell