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Offline Gutbucket

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Re: Oddball microphone techniques
« Reply #195 on: April 08, 2016, 05:35:04 PM »
Straight outa Hollywood Woodstock, of course.

[edited for improved punchline]
« Last Edit: April 21, 2016, 03:45:00 PM by Gutbucket »
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Offline rocksuitcase

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Re: Oddball microphone techniques
« Reply #196 on: April 09, 2016, 11:53:11 AM »
GB, kindms says you have infected our minds with your oddball mic techniques! I say it is a very good thing!  8)
While we would probably reserve this pattern for outdoors, we had a chance to record one of our favorite bands, and another old favorite of mine indoors last night in Saratoga Springs NY.
We had a newly purchased ck22 capsule to test since we now have two so:
what you have here is the two ck22's on the 460 pre-amps spaced at 90 cm, and the AKG 414 XLSII's both in figure 8, but one facing forward and the other at 90 to it (facing sideways).
Once we get them processed we will share.
Once again, thank you for infecting errrr showing us some new ways to use our microphones!    >:D
« Last Edit: April 10, 2016, 09:06:30 AM by rocksuitcase »
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Offline Gutbucket

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Re: Oddball microphone techniques
« Reply #197 on: April 11, 2016, 10:56:07 AM »
YES!

Funky looking setup for sure, love it.  I've been curious about using a forward facing figure 8 rather than other patterns in the center between the omnis.  I've run Blumlein (X/Y 8s) between the omnis years back, pictured rather early on in this thread I think (using ADK TLs and later a Peluso P-Stereo LD mic), but I don't think I played with summing the two Blumlein channels together equally to form the equivalent of a single forward facing 8.  I think I ran the Blumlien as M/S a few times two like you are doing here.  Might have to dig up and revisit those recordings.

A center forward facing 8 between the omnis interests me due to what it may do for the 3-mic imaging and the distribution of reverberance and audience ambience across the playback image.  The 8 pattern has the tightest forward lobe of any 1st order pattern, which produces the most-rapid fall-off in level as the source moves off-axis.  Sound arriving from 45 degrees off axis is -3dB down in level, and level drops off rapidly beyond that at angle of arrival approaches 90 degrees off-axis.  So depending on the appropriate mix level balance we end up with between the omnis and the forward facing 8, we get some interesting behavior. 

Say we set mix levels so that sound arriving from directly ahead will be 3dB louder through the center channel than the omnis.  Sound arriving from 45 degrees off center will be picked up with equal level in all three channels, and sound arriving from anywhere in the plane perpendicular to forward facing axis 90-degrees off to either side, below and above, will be picked up only by the omnis.   That gives us a +6dB Mid verses Side level difference at minimum in the resulting 3 mic mix for sounds arriving from directly in front compared to those arriving from anywhere in the plane perpendicular to forward axis, producing good fore/aft reach for the "center image stuff" and pulling the off-axis ambient audience and room 'verb stuff out to the edges of the playback image.

Putting a 3rd omni in the center goes a long way towards fixing the primary problem with a spaced omni pair.  But a directional mic in the center improves upon the spaced omnis in these other ways as well- increased fwd sensitivity bias, and sharpened directional imaging.  An 8 in the middle may be the most optimal for improvement of directional imaging, where as a supercard (or shotgun) is going to be most optimal for improvement of forward sensitivity.
 
At first glance, the two omnis + center forward facing 8 array would seem fully symmetrical in terms of front/back sensitivity, but it should actually produce some forward sensitivity bias at lower frequencies where the spacing between the omnis and 8 becomes acoustically small in terms of wavelength, because at those frequencies the combination of omnis and 8 will produce a forward facing cardioid shaped sensitivity pattern.

Inside, I'd be tempted to set the forward facing (Mid) 414 to supercard or hypercard pattern, to get more of that forward sensitivity bias across all frequencies.  Without the omnis, that makes the M/S center pair sort of a more forward biased version of M/S Blumlein.
« Last Edit: April 11, 2016, 02:23:14 PM by Gutbucket »
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Offline Gutbucket

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Re: Oddball microphone techniques
« Reply #198 on: April 11, 2016, 11:28:12 AM »
In the small amount of playing with stereo mixdown playback of the recordings made at Springfest last month from the latest array I posted pictures of above, I've found turning the center mic into a M/S pair is very useful in combination with the omnis alone, and far less important but still possibly helpful when the sideways facing OCT supercardioids are in play as well. 

Perhaps not surprisingly, when only listening to the center M/S pair on it's own, use of a lot more Side-channel in the decode ratio is appropriate.  In combination with the spaced omnis, less Side is most appropriate, and in combination with both the omnis and the sideways facing OCT supercards, very little Side component if any works best.  In that case, the sideways facing OCT supercards are already contributing plenty of rich near-spaced 'Side' information.  However, in all cases I seem to prefer at least a slight touch of Side from the M/S pair, which seems to make the stereo image spread slightly smoother across center and less center detented when the center is mixed in at higher levels.  But that might be because I was using a supercard center microphone to maximize direct pickup over ambient pickup in that channel,  instead of a cardioid (or even omni) center called for with the OCT technique.  If I switched to a cardioid center, or perhaps spaced the side-facing OCT supercards a bit less far apart, I may not need any additional Side from the M/S 8 to "slightly open and unstick" the center.

So I think in terms of practicality, I'd probably choose either OCT + omnis, or M/S + omnis, rather than both, unless it's easy and I have plenty of recording channels to spare.  But it's a bit too early for conclusions so the experiment continues..  This weekend at Wanee I'm going to limit the channel count to 6 so I don't need to haul and power the V3, and will probably do that by eliminating the rear facing pair all together.  I plan to record the wide-spaced omnis, OCT supercards and center forward-facing M/S pair.  This will allow for more listening to combinations of spaced omni and/or OCT and/or M/S center recordings made in a different recording environment- still outside, but recording from further back at the soundboard in a much bigger outdoor stage setup.  Also the music is less acoustic Americana stuff and more amplified rock stuff.  Likely recording from within the board cage (or immediately adjacent to it), with the board tent and a beer tent immediately behind, so there isn't the same clean rear audience ambiance I'd want to pickup from behind as there is when recording from well FOB in the "excitement zone".

Rocksuitcase- My suggestion in playing with your combination mix is to try bringing up the omnis first, then the center (Mid) 8 in combination with the omnis, and once you get a good level balance between those three, play with adjusting the M/S ratio by bringing the Side 8 into play.
« Last Edit: April 11, 2016, 02:42:41 PM by Gutbucket »
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Offline Moke

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Re: Oddball microphone techniques
« Reply #199 on: April 11, 2016, 11:51:12 AM »
I played around a bit this weekend. I ran a baffle disc with my DPA4060 pair. I also ran a sub-card directly over the top of the baffle, at 0º, and vertically time aligned to the 4060 pair, for a three mic mix.
For me, it is an unusual departure from my two channel stereo approach.
I'm still playing around with it a bit, to see if I like the results.
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Offline rocksuitcase

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Re: Oddball microphone techniques
« Reply #200 on: April 11, 2016, 12:05:01 PM »
I so I think in terms of practicality, I'd probably choose either OCT + omnis, or M/S + omnis.   But the experiment continues.. This weekend at Wanee I'll probably limit the channel count to 6 so I don't need to haul and power the V3, by eliminating the rear facing pair all together. I plan to record the wide omnis, OCT supercards and M/S center pair.  That will allow for more listening to those combinations of recordings made in a different recording environment- still outside, but recording from further back at the soundboard in a much bigger outdoor stage setup.  If recording from within the board cage, with the board tent and beer tent immediately behind the board, there isn't much clean rear audience ambiance I'd want to pickup from behind anyway, as there is when well FOB.

Rocksuitcase- My suggestion in playing with your combination mix is to try bringing up the omnis first, then the center (Mid) 8 in combination with the omnis, and once you get a good level balance between those three, play with adjusting the M/S ratio the Side 8 into play.
We found the V2/V3's sure do suck up a bunch of power, even using the Eco-Charge SLA's!

kindms will be mixing this, and I have directed him to this thread. Thanks for your tips!
What I can say is that we decided to listen to it with the forward facing figure 8 and the two omni channels. We found that pushing the single mid channel up by about 4 dB put just enough oomph in it to really bring out some depth and not so oddly to "reduce" the annoying effect of the chatterers!
We will keep you posted when the shows get upped.
Thanks once again for infecting errr influencing us to try new things!   ;D
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Offline Moke

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Re: Oddball microphone techniques
« Reply #202 on: April 14, 2016, 08:36:42 PM »
A question about mixing a three mic recording.  I ask, because I've never run an M/S array before.

I ran with my DPA4060 pair as baffled omnis; nothing too unusual about this.  I typically use a rather tight spacing from the disc face. But this time, went even closer, ~1" naway from the disc face, each side.
I also ran a single L.A. CM3 sub-card directly over the baffle, and maybe only 2" in front of the omni pair; so the timing alignment is really quite close.
In post, and after I did my main mix, I farted around with trying a quasi-M/S mix by taking the omni pair and flipping the phase on the left channel of the baffled mics.
In the mix, it sounds great thru headphones; but presently, my main stereo amp that is hooked up to the DAC/Computer, seems to want to be a two channel mono amp, so I'm not getting any stereo separation, except via headphones.

The mix consisted of the tightly spaced baffled omni pair, with the center sub-card mic sounding best when left a couple of dB below the omni pair.

OK,.... thoughts?  Am I right in thinking this might be called a quasi-M/S mix? Can the pair of tightly spaced omnis be thought of as a figure of eight response with an omni low end?
 
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Offline 2manyrocks

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Re: Oddball microphone techniques
« Reply #203 on: April 14, 2016, 11:39:13 PM »
^don't believe its m/s.  M/s could be possible with two cards on each side with one omni in the center, but one figure8 for the sides LR is the usual mic of choice.  My limited understanding is alignment of the card capsules is the problem and why a fig 8 pattern is normally used instead.

Having two Omni's for LR is why you sense mono when you playback. 

At least that is what I think, but I may be mistaken.


Offline John Willett

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Re: Oddball microphone techniques
« Reply #204 on: April 15, 2016, 04:40:25 AM »
A question about mixing a three mic recording.  I ask, because I've never run an M/S array before.

I ran with my DPA4060 pair as baffled omnis; nothing too unusual about this.  I typically use a rather tight spacing from the disc face. But this time, went even closer, ~1" naway from the disc face, each side.
I also ran a single L.A. CM3 sub-card directly over the baffle, and maybe only 2" in front of the omni pair; so the timing alignment is really quite close.
In post, and after I did my main mix, I farted around with trying a quasi-M/S mix by taking the omni pair and flipping the phase on the left channel of the baffled mics.
In the mix, it sounds great thru headphones; but presently, my main stereo amp that is hooked up to the DAC/Computer, seems to want to be a two channel mono amp, so I'm not getting any stereo separation, except via headphones.

The mix consisted of the tightly spaced baffled omni pair, with the center sub-card mic sounding best when left a couple of dB below the omni pair.

OK,.... thoughts?  Am I right in thinking this might be called a quasi-M/S mix? Can the pair of tightly spaced omnis be thought of as a figure of eight response with an omni low end?
 
The rig can be seen here:
http://taperssection.com/index.php?topic=176324.msg2184245#msg2184245

No - this is not MS in any way.

You may find it an effective recording method - but it's *NOT* MS.

Offline Moke

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Re: Oddball microphone techniques
« Reply #205 on: April 16, 2016, 04:21:27 PM »
OK,... thanks.
I guess I'll call it sub-card_mid/omni-8_side.
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Offline voltronic

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Re: Oddball microphone techniques
« Reply #206 on: April 16, 2016, 05:23:39 PM »
^don't believe its m/s.  M/s could be possible with two cards on each side with one omni in the center, but one figure8 for the sides LR is the usual mic of choice.  My limited understanding is alignment of the card capsules is the problem and why a fig 8 pattern is normally used instead.

Yes, you want a figure-8 Mid mic.  Not only that, some people will tell you that to really make a proper M/S recording, you should only use a single-diaphragm figure-8, rather than  a dual-diaphragm arrangement (either fixed or in a multipattern mic) which is less expensive but much more common.  Others here will be better equipped to speak to how valid that advice may or may not be.  There are only three single-diaphragm figure-8 condenser mics out there I know of: the Senn MKH 30, Schoeps MK8, and Neumann KK 120, and they're all pretty expensive.  My experience doing M/S with the Schoeps MK4/MK8 combo tells me they're worth it, though.  You could use ribbons which are always figure-8 and obviously also single-diaphragm, but I don't know how well they would mix tonally with a non-ribbon Mid mic.  Or you can use two ribbons in a Blumlein setup, and that solves that the tonal balance problem at the expense of your bank account.

Side note: I just now realized that DPA doesn't offer a figure-8 mic at all; they must be one of the only high-end mic builders not to offer that option, even in a multi-pattern mic.
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Offline Gutbucket

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Re: Oddball microphone techniques
« Reply #207 on: April 18, 2016, 12:46:45 PM »
Ha! Thanks for the paint-stick adapter post, Walter.

Mike, you can theoretically produce a dipole (figure 8 pattern) using two closely spaced omnis.  To do so you'd invert the polarity of one of them then sum them together.  Problem is that then they mostly cancel each other out that way and produce very little output.   The closer together, the better the dipole but the greater the cancellation too.  Without the two mics mounted very close together there will be less cancellation at high frequencies, but at that point you'll no longer have a figure-8 pattern with uniform phase and reverse polarity, you'll instead get the random phase relationship spaced omnis provide.

However, in the situation you describe above, you have the advantage of a baffle between the two omnis.  The mics are mounted quite closely together and are also no longer acting like omnis at all frequencies.  The baffle will make them behave somewhat like back-to-back opposed cardioids at high frequencies. 

I wouldn't call it a normal Mid/Side setup, but if you want to try a mid-side mix, here is how you can go about doing it-

Load the two omni channels into your editor.
Invert the phase of the right omni only.
Sum the two omnis and adjust the relative levels of the two to achieve the maximum cancellation possible.  Low and low mid frequencies should cancel significantly, you should hear only high mids and highs in the resulting mix of the two.
Save that sum as your "synthesized figure 8 Side" file, then use it as you would a regular Side signal from a single figure 8.

It will not work to simply sum the Mid and left omni and route that Left, and sum the Mid and inverted polarity right omni and route that Right.   Or rather that will produce sound,  but will not be a M/S manipulation. You need to first sum the omnis with one of them inverted to produce the Side signal, then use that side signal the normal way along with the Mid signal in a M/S matrix.

Since the omni-difference Side signal will be mostly high-frequency information, the resulting M/S output will be strongly monoized at low and mid frequencies and have increasing stereo width up top. 

Should be an interesting experiment.  I suspect the straight-up baffled omnis plus some amount center to taste will work best for you though.
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Offline Moke

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Re: Oddball microphone techniques
« Reply #208 on: April 18, 2016, 01:20:50 PM »
Thank you very much GB! You understand the concept to which I was eluding.
I messed around a bit with it. I flipped the wrong channel polarity; left channel flipped, not right. 
Also, I don't think that I have an MS decoder available in the editing programs that I have (Audacity, Sound Studios, Reaper).
I've got some homework to do in tracking down an MS decoder ring. So I will try to mess with it a bit later.
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Offline Gutbucket

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Re: Oddball microphone techniques
« Reply #209 on: April 18, 2016, 01:53:35 PM »
Once you have a Side signal, you can "roll your own" MS decoder in your sound editor if you like rather than using a M/S decoder plugin.  It's a lot easier and straightforward if you do the step outlined above to produce the side channel first, rather than attempting to do both parts in a single editing session.

Once you have both Mid and Side channel files, you can produce Left/Right using three channels in the editor-
Mix Mid and Side to produce the virtual Left microphone.
Mix Mid and polarity inverted Side to produce the virtual Right microphone.

You'll probably want both Side levels to be similar, yet keeping the side levels matched absolutely is no longer critical at that point.   If you were to use a bit more inverted Side for virtual Right than non-inverted Side for virtual Left, you'd simply be changing the pattern and angle of the virtual microphone on that side independently of the other side.  That could be useful in some situations where the situation is unbalanced left/right, like recording from off to one side or whatever.

Or you can simply download a VST plugin.  Many are free.  Here's a page link to the free Voxengo MSED plugin which is very useful- http://www.voxengo.com/product/msed/ It includes two M/S instances in the single plugin, so in addition to the simple task of decoding a Mid/Side recording to Left/Right (or switching a L/R recording to M/S), you can also feed it a L/R signal, adjust the Mid/Side balance of it to your liking, and have it output the modified L/R signal again.  That can be very useful for mastering.  You can use it to make stereo width adjustments on any stereo recording, or to process the Mid information differently than the Side info before recombining them to Left/Right.
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