Topic: Schoeps mk6 figure 8 frequency response curve.

[yug du nord]

Gutbucket...  I'll try to play around with the DMS tool some more today and try to answer some of your questions.

Like I said, this is new software to me.....  so maybe I don't know how to use it correctly yet.......  but it seems to be working nicely for M/S in my first outing with it. 
I'll report back after I play with it some more. 

This could be the first time that I've ever disagreed with DSatz.....  this plug-in might be magic!   

[Gutbucket]

Thank you sir D.  Safe travels.

Ungleyug: Not magic when you know how it works, but can still be awe inspiring.  I use a similar ambisonic decoder and it's pretty amazing even knowing what's going on under the hood!

Still doesn't make any sense to me.

The way i understand the double MS, there are two cardioid elements one at 0 degrees and one at 180. By summing and phase, one can arrive at a single, mono microphone pattern- in largely the same way dual diaphragm LD microphones can have a continuously variable pattern (let's not debate weather or not the "omni" pattern created is "real").

In the schoeps DMS decoder, that rear facing cardioid microphone can also give rear channel information.

But, if there is no rear facing element, how can the pattern be varied at all?

You have it right.  I'll work though it..


Here’s the deal: A cardioid pattern is equivalent to the sum of and omni and a figure-8 mixed at equal signal levels. 

If you have forward and backward facing cardioids, then a straight sum of the two adds their omni components.  The figure-8 components of the two cancel out, since they face opposite directions and have opposite polarity.  So you end up with just the omni part X 2. 

If you change the polarity of one of the microphones first (say the backward facing one) then the omni components have opposite polarity so they cancel out and the figure-8 components add together so you end up with just the figure-8 part X 2 (forward facing).

By mixing the two in different amounts (changing the ratio) you get different patterns between omni and figure-8.  And by changing the polarity of one or the other you point that pattern forward or backwards.  Cool so far?



What the Dual M/S plugin probably does is apply capsule equalization to the files first,  then sums the forward and back facing cardioids and divides the result by 2 to get an omni.  It also takes the same forward and back facing cardioids and inverts the polarity of the back one before summing them and dividing by 2 to get a forward facing figure 8.

The plugin then has 3 basic patterns to work with: an omni, a forward facing figure-8 and the side facing figure-8.  That’s horizontal only ambisonic B-format.  It’s then straight forward to mathematically derive first order patterns pointing in any horizontal direction, with patterns and angles independent of each other.


If the rear facing cardioid isn’t there, the program does the same math.  It sums the forward facing cardioid with zero (the missing back mic) and gets a forward facing cardioid instead of an omni.  It also sums the forward facing cardioid with the inverted polarity the missing back mic (negative zero) and gets a forward facing cardioid instead of a forward facing figure-8.

It then does the same B-format processing, but the omni (W component) and the forward facing figure-8 (Y component) are actually forward facing cardioids instead of the expected omni and 8.  So if you set the program to give you just a mono omni, it thinks it is doing that and displays an omni on screen, but the audio output is a forward cardioid.

Without the extra back facing cardioid, the output of the plugin becomes standard two channel M/S decoder, but the graphics and controls don’t realize the back cardioid is missing and still act like it’s working with all three signals.

The reason I suggested dialing in a mono mid and changing the pattern from omni through figure-8 and back and listening for timbre vs level changes is because if what I outline above is correct, the actual audio output will be a forward cardioid for all of those settings, but the output should increase in level as you adjust things toward the cardioid position in the middle of the adjustment range and decrease in level towards the omni or figure-8 settings.  That’s because the plugin is expecting the rear facing cardioid and is still dividing the sums involving it by 2. If you specify a forward facing cardioid, it doesn’t do that and the resulting output level should be higher.

If you did include the backward facing cardioid input, then doing the same would change the pattern from omni through cardioid to figure-8 as expected (and as displayed) and the timbre of the sound would likey change, but the level should not.

Hope it makes sense and I hope I got it all straight.

[noahbickart]

got it.

It seems like double m-s might be a great option for those who can record 3 channels.

[yug du nord]

After further review, my experience with the DMS is as Gutbucket describes.  I know that the rear information is not there in my standard M/S file.....   but when shifting the "polar pattern" dial around, it visually formed different, various patterns....   but also shifted the sound around.  But it turns out that when using standard two-channel M/S, the "polar pattern" dial acts the same as the "microphone angle" dial...  but kinda opposite on the dial as the "polar pattern" dial.  So with my being rather excited to play with this tool....   I've had the file for a year or more, but never loaded it into my DAW....  and finally got it loaded yesterday, I was overly rambunctious!  My mistake.

It does seem to work great as a two-channel M/S tool also.  Much quicker and more precise than my "copy/paste/invert" method. 

Am I missing anything regarding if this an appropriate/inappropriate tool for standard M/S?
I don't need to be mixing any "invisible/non-existent" surround channels into my standard, two-channel M/S decoding..... 

Thanks for the help....  sorry for the misinformation.


edit:  FYI:  I modified my earlier posts regarding the false info that I've reported.

[Gutbucket]

Am I missing anything regarding if this an appropriate/inappropriate tool for standard M/S?
I don't need to be mixing any "invisible/non-existent" surround channels into my standard, two-channel M/S decoding..... 

Thanks for testing it. 

You're not missing anything and the plugin should work fine for standard M/S as long as you ignore the display and inconsistent knob interactions.  If you just adjust settings while listening until you home in on the best setting, it's all good.  Who cares what the actual pattern and angles actually are, unless you are trying to duplicate the same setup again later? 

I've actually done that by remembering what decoded angle and pattern worked out best in a particular situation. Then when the same band setup the same way in the same room again, and I was setup in exactly the same location but recording using a different setup with two standard coincident mics, I arranged that pair to duplicate the settings that I arrived at previously.  Otherwise I would never have set them up the way I did- as a M/S pair with a hyper mid at center stagelip, directly in front of the drum kit but angled more than 30 degrees to the left to balance a guitar amp over on that side louder than everything else, but it worked out great.

You don't need to worry about accidentally mixing in any surround channel stuff to the stereo output.  The surround channel outputs of the plugin may or may not output something, but just ignore that.  Just to be clear, you are changing the pattern, but at the same time as the angle.  The relationship is linked.  The pattern will always be supercardioid-ish for the settings you end up with but will be more cardioid-ish at narrow angles and more figure-8-ish at wider angles.

[Gutbucket]

Seems to me Schoeps should modify the plugin to display correctly and eliminate the mislabled controls in this situation by either having a manually selectable two channel M/S mode, or by having it detect the absense of a the rear facing cardioid input and automatically enter standard two channel M/S mode.

[yug du nord]

You can just MUTE the "C, LS, RS" channels so that you're left with just the "L,R" channel. 
It's new to me though the way that adjusting the angles is so simple....  so if I "create" a cardioid pattern with the "Polar Pattern" dial, it's kinda neat IMO that you can visually see the angle of the stereo cardioid pattern move accordingly. 
IMO as awesome as the display is,  I agree that it could use a simple, selectable two channel M/S mode to ease the confusion a bit. 
But it is a very simple plug-in to work with!

[WiFiJeff]

got it.

It seems like double m-s might be a great option for those who can record 3 channels.

Another way to do this is with a forward (as well as side) facing figure-8 and an omni cap, the sum will give a forward facing cardiod and the reverse polarity forward figure-8 sum with the omni will give a backward facing cardioid.  This is what my new Josephson C700S does.  I have only made one recording so far (next concert, with vocalist, is Friday), but the feedback is good.  A friend with lots of high-end listening equipment writes: "The sound of the C700S is very striking.... It's like increasing my musical IQ, you hear so much more information...there are no words to describe this. Every note is so much more interesting, you just have to sit up and listen."

Shoulda got the C700S four years ago.

Jeff

[yug du nord]

^are you using the Josephson on stage/above stage/distant from stage?  just curious how you utilize the surround sound??.....

[WiFiJeff]

The hall is a geodesic dome lecture hall with stadium seating, very good if lively acoustics.  The soloists generally locate forward of halfway between the lowest row of seats, which is level with the "stage," and the curved back wall.  My stand goes on "stage" near the seats, center.  I raise the mics about 7-8 feet up and aimed down at the talent.  That's how I've run an AKG C426B Blumlein for a few years, and how the folks at Josephson think I should use the C700S too.  When I run omnis on a Jecklin disc or Schoeps MK22s on a Vark bar I generally place them similarly.  I have not dine any 5.1 mixes yet, but hope to experiment soon.

Because the stand is on the same floor as the performers, I have had issues with feet taping, something that goes directly up my stand to create a nasty bass clunk.  The internal suspension of the C700S seems to minimize this, but I have not yet had enough experience with it to be sure.

Jeff

[Gutbucket]

Jeff, I'm curious if you arrived at the 7-8' up and aimed down a the talent mic position on the sound picked up from the performers or room alone or for other reasons such as getting the body of the mic above sightliness or reducing pickup of the audience by angling the rear lobes upwards. 

I ask because I know the raised above pointing down at an angle setup is common, often with the mics higher than 7-8', but I almost always run similar Blumelin/ambisonic setups lower, with the mic pickup plane arranged horizontally, simply for practical reasons.  I haven't compared the difference in sound of that with angling the mic down so it's pickup plane is no longer horizontal.  Might depend on the room, the instrumentation, and the audience I suppose.  Maybe I should make an effort to give that a try.

[WiFiJeff]

I find that the sound is best at that height (the sightlines for a raised mic are not the issue, with stadium seating you can't get high enough not to block someone!).  I have gotten some nice recordings of string quartets lower down and more horizontal, but also then pick up a bit too much of the page-turning, breathing and humming that goes on.  I might experiment a bit with this, but for piano I'm pretty sure I've got a good optimum.

Jeff

[Gutbucket]

Funny you mention piano, which was party my motivation for asking.  It can be a difficult instument to record well horizontally and I've imaged a raised position could work better.  I can see it cutting down on humming and nose-whistling and possibly page-turns with string players.  Have you had any issues with the violin/viola getting screachy from above?

[WiFiJeff]

I haven't noticed this, but basically I just get a chance to set up and check levels, no relocating based on careful sound tests.  My bigest fear on violin and viola is that when the hall fills up the soloist, seeing tiers of people rather than the empty seats that were there when he/she was warming up and I was setting up, will step back away, doubling the distance from the mic stand and throwing off the balance with a piano that stands still.  Going up helps mitigate this a bit, too, as the distance changes proportionately less.

Jeff

[Gutbucket]

Thanks.

Appologies for the off topic mid-thread lane change.