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Gear / Technical Help => Microphones & Setup => Topic started by: thunderbolt on September 29, 2011, 04:19:35 PM
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Since I haven't done Blumlein before, I want to make sure I'm orienting the capsules correctly.
It is this (figure eights at 90 degrees, one left and one right 45 degrees from center)
Source
X
Where the "east" and "west" openings are the null points. (The X is only to illustrate, because it would be more accurately represented by a cross turned counterclockwise 45 degrees.)
Rather than this
Source
+
which would really be more of a M-S configuration (e.g., in a cardioid-blumlein, one mic facing straight ahead, and a figure eight 90 degrees off axis).
Is this correct?
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The X is correct
source
X
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Blumlein
(http://i1108.photobucket.com/albums/h413/akgmike/4sale/my%20AKGs/DSCN1423copy2.jpg)
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Source
+
which would really be more of a M-S configuration (e.g., in a cardioid-blumlein, one mic facing straight ahead, and a figure eight 90 degrees off axis).
As long as you use 2 figure 8 patterns, you could do an M-S blumlein with an adjustable angle.
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The good Mr. Blumlein did it both ways.
Most think of it with 'X' orientation, but either are correct and both work well. '+' M/S orientation is better if you have two mis-matched or different mics since it makes any error due to those differences symetrically distibuted between the center and both sides evenly, instead of between left verses right. 'x' orientation is simple since it doesn't need any decoding for playback and might technically work better if your figure 8 mics have a slightly different response to the back than to the front as some do, since it makes those error symetrical left to right. If really serious about it and equally open to doing it either way, and you have well matched mics with even response in both directions, then consider '+' when the sound source is primarily centered (it puts the mid mic directly on-axis), and 'x' for mostly PA amped gigs so the mics are more on-axis with stacks as the primary sources of sound, but that's probably splitting hairs.
Blumlein himself reportedly prefered using the M/S orientation, but probably doesn't mean that much. He was doing other signal manipulation stuff and M/S converting anyway. Keep in mind that mic technology has changed significantly a bit in the intervening 80 years. He was using the very first figure 8 mics, which likey had major limitations in comparison to the mics we use. ;)
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I ran Blumlein last night with the '+' M/S orientation simply because I wanted to use the mid channel for another array as well and didn't want to have to mess with decoding to get a forward facing 8 for it. Otherwise I would have done it as 'x'. Of course now I need to decode the M/S for Blumlein but that's fine. The point is that what made up my mind about which way to do it was a different factor altogether and I didn't feel like I needed to worry about other the other stuff.
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Thanks for all the helpful replies. I appreciate it. M-S with two figure eights sounds very interesting. Doesn't seem like too many people try it.
On a separate note, regarding M-S: When using a recorder with a built-in or add-on M-S matrix decoder, do you pan hard right and left for the recording and adjust the width of the stereo field in post, or do you get a "rough" matrix mix while recording, and then fine-tune in post?
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Most choose to record the mid and side channels separately, so they can dial in the best settings later when able to listen more acurately. Using the recorder's M/S matrix on the record side (or the mic's, some M/S mics offer the option of switching between M/S or X/Y output) is most useful if you want to setup the mics as M/S but don't want to bother with decoding it to a regular stereo X/Y later.
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If you got the Milab DC196's you can run Blumlein like this:
http://taperssection.com/index.php/topic,111000.msg1483734.html#msg1483734 (http://taperssection.com/index.php/topic,111000.msg1483734.html#msg1483734)
(http://taperssection.com/index.php?action=dlattach;topic=111000.0;attach=86834;image)
super cool! some day... I'll have a pair!
--Ian
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If you got the Milab DC196's you can run Blumlein like this:
http://taperssection.com/index.php/topic,111000.msg1483734.html#msg1483734 (http://taperssection.com/index.php/topic,111000.msg1483734.html#msg1483734)
(http://taperssection.com/index.php?action=dlattach;topic=111000.0;attach=86834;image)
super cool! some day... I'll have a pair!
--Ian
The 196s are unique in that since the diaphragm is rectangular, you can alter the pickup pattern for where you want the widest covered direction (either vertical or horizontal), so chosing between vertical alignment like the akg414 picture or the horizontal setup means more then just sheer logistics. It doesn't make much difference, but it evidently makes some.
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If you got the Milab DC196's you can run Blumlein like this:
http://taperssection.com/index.php/topic,111000.msg1483734.html#msg1483734 (http://taperssection.com/index.php/topic,111000.msg1483734.html#msg1483734)
(http://taperssection.com/index.php?action=dlattach;topic=111000.0;attach=86834;image)
super cool! some day... I'll have a pair!
--Ian
The 196s are unique in that since the diaphragm is rectangular, you can alter the pickup pattern for where you want the widest covered direction (either vertical or horizontal), so chosing between vertical alignment like the akg414 picture or the horizontal setup means more then just sheer logistics. It doesn't make much difference, but it evidently makes some.
Page makes a good point. Even with mics that have round diaphragms (where the response of the diaphragm itself should be symmetrical)*, horizontal verses vertical orientation of the mic body might make somewhat of a difference. That's because one of the unique aspects of the Blumlien configuration is that it picks up sound evenly and without bias for all horizontal directions across a full 360 degrees. The polarity changes from quadrant to quadrant, but ideally sensitivity doesn’t change at all for any horizontal direction. So the presence of any object near the capsules has much more potential to make a sonic difference than with other stereo mic configurations which favor sound arriving from the forward direction. That includes the presence of microphone bodies themselves. It might not make a huge difference, and at least any differences it does make should manifest symmetrically left/right on playback, but it’s something to consider.
I prefer the vertical orientation, mostly because it is more compact and less visually intrusive.. I consider the better horizontal symmetry and more open space in the horizontal plane around the capsules a bonus, even if it doesn’t make a big differnece. I realize that many might setup Blumlein with the mic bodies horizontal simply because it might be easier to do with whatever mounts are available.
Figure 8 mics with rectangular elements like these Milabs, some Pearls, and ribbon mics don’t have the same response horizontally and vertically. I’d be more wary of setting them up with the bodies horizontal as pictured for that reason and would make a stronger effort to run in a vertical orientation. With the bodies horizontal, the figure-8 pattern in the horizontal plane is likely to be less accurate, When set up with the bodies vertical, that same response characteristic should produce a somewhat more reduced sensitivity for sounds arriving off axis above and below the horizontal plane than round diaphragm mics. That could be considered beneficial (a feature, not a bug).
* unlike speakers, I’ve never seen a polar plot of response in the vertical plane for any microphone. Maybe Milab publishes them to show how their rectangular capsule response changes with orientation. If so I’d love to see it.
In the horizontal plane, some figure 8 ribbon microphones do not have a symmetrical response between their front and back sides and that difference should be apparent on standard horizontal pickup pattern plots. Two of those mics would be better set for Blumlein in the ‘x’ configuration than the ‘+’ configuration so the different response of the ‘back side’ of both mics points either to the front or the rear, with left/right symmetry.
Just an idea, but those Milabs are so small you might be able to take that standard Sure vert bar apart and flip the sections around so the mic attachment points are at the top and bottom ends of the bar instead of the center and have enough room to mount the mics vertically. To do that with bigger mics, people mod the bar with a longer threaded rod and a spacer section in the middle between sections, but if those Milabs are small enough, you may get lucky and be able to do it with the stock bar. Those are really cool mics, I’ve wanted to try a pair for a long time.
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Don't get me wrong, I don't doubt the Milabs are capable of making fantastic recordings arranged as Blumlein with the bodies in the horizontal orientation. This is all minutiae, but discussion this stuff is what TS is for right?
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This is all minutiae, but discussion this stuff is what TS is for right?
exactly. ;D
I was going to make a snarky venn diagram, but that took effort.
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More rectangular element Blumlein minutiea-
Assuming the Milab's figure-8 response in the vertical plane just cuts off more sharply to a wider null region between front and back than it does in the horizontal plane, which is supposedly what it does and how a vertically oriented regtangular element should behave in theory.. and assuming that it does so in reality just as smoothly (which is the more suspect part in my thinking).. and ignoring any influence that mic bodies might have in the horizontal plane as mentioned above.. then.. (whew, this is getting almost like lawyer speak!)
..Then, with the Milab bodies setup horizontally, you might want to angle them a bit less than the standard 90 degree inclusive angle for the most even imaging across the stereo soundstage. Polar plots indicating a different position of the -6dB off axis point in the vertical verses horizontal plane would suggest if that would make any difference or not.
[/recording geek minutiea]
:P Where else do I get to talk about this stuff?
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Speaking with a fellow TS'er this weekend whom wants to go Blumlein...we spoke about phase on the Figure 8...I got the proverbial blank stare
(http://upload.wikimedia.org/wikipedia/commons/thumb/7/71/Blumlein_-Stereo.png/250px-Blumlein_-Stereo.png)
As in the diagram above...it appears to me that one lobe is the opposite phase of the other...one side Positive and the other Negative...This is also what makes decoding MS possible... Left = Mid + Side, Right = Mid − Side
Did I miss something in Figure 8 101???
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You got it.
To be technically accurate and hopefully reduce confusion, the opposing sides of a figure-8 microphone have opposite polarity not phase, but that (mis)use of the term phase is pretty common.
It's true that the opposite polarity lobes of the side mic is part of what makes M/S possible, yet the mid mic doesn't need an opposite polarity lobe- there is one in the case of M/S Blumlein or if you use a supercardioid mid mic, there isn't if you use a cardioid or omni for the mid mic.
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Ah...Polarity not phase thanks...that is most likely the reason for the look...