Topic: Oddball microphone technique (OMT) - part 3

[Gutbucket]

[..] it integrated perfectly into the stereo image when panned as pointed with respect to the overall array. It does not come out sounding asymmetrical.

I assumed that channel was panned center in the mix, or wherever it needed to be to reinforce the the apparent center of the direct-sound portion of the image.  Are you saying instead it worked best panned so as to emulate the same angle in which it was physically pointed?  If so that something of a head-scratcher.

Forgive me if we already talked about this back when. 

[EmRR]

[..] it integrated perfectly into the stereo image when panned as pointed with respect to the overall array. It does not come out sounding asymmetrical.

I assumed that channel was panned center in the mix, or wherever it needed to be to reinforce the the apparent center of the direct-sound portion of the image.  Are you saying instead it worked best panned so as to emulate the same angle in which it was physically pointed?  If so that something of a head-scratcher.

Forgive me if we already talked about this back when.

Yes, you're reading that correctly. 

[Gutbucket]

So counter-intuitive.  I'll have to think about that some more.

[EmRR]

Maintaining relative phase must have a lot to do with it.  If you pan center, it tilts the image opposite the original angle. 

[Gutbucket]

Might be.. maybe in its interaction with the signals from the mics spaced away from it.  It should in theory retain the the same phase relationship with any mics it was coincident with regardless of pan position, excepting any artifacts from a real world realized, never quite totally perfect coincident alignment. 

How well left/right balanced was the sound in the recording position to begin with during the performance?  Was it well balanced enough that the decision to point the shotgun toward one PA rather than the other was arbitrary or was that side significantly louder?


One thing I like about these arrays is a somewhat greater ability to re-balance a lopsided image afterward.  Usually I do that through some combination of level balancing the various pairs in combination with panning the center Mid - whatever works and sounds right.  Can only do so much with the spaced pairs level-panning wise without throwing the overall level/power distribution out of whack, so panning any mono center contributor becomes a powerful tool for centering things.  Even though that also alters the power distribution it seems to do so less severely for the same amount of correction in the mix.  If I get the power distribution of the spaced mics about right, I can sort of force center balance with center signal panning.

The thing is, to bring the center image back to where it should be by panning the mono center stuff, I'm compensating by panning toward the quieter side.  What's odd is that's the opposite of what you describe (I'm presuming here that the center shotgun was pointed toward the louder PA side), and yet the resulting playback image remains balanced with it panned the opposite way, toward what was presumably the louder side rather than away from it.


Part of what may be going on is another thing I like about the arrays subjectively, yet sometimes nags me a bit philosophically in an objective sense, which is this- L/R imbalances seem less problematic overall and somewhat less nakedly obvious in general.  Sure I hear them and work to correct them, but they often aren't as severe as I expected them to be when I was making the recording.  Now that could be that in order to listen to the recording I'm going through some of that balancing process anyway in getting the various channels roughed in (less the center panning part).  What nags me is a niggling thought that if it were unbalanced live, I'd think that imbalance would be conveyed in something of a more obvious (accurate?) way, even though to some extent it is, just somewhat less than I expected. Might be that the well-conveyed, general sense of openness and immersion, which tends not to be unbalanced, sort of covers for that.

Then I remind myself that this is all an auditory illusion anyway, and the ultimate goal of these arrays was never absolute localisation accuracy which perfectly corresponds 1:1 with real-world source placement, but a convincingly real sounding recording with seemingly accurate and precise source placement that supports the musical listening experience.  Maybe these arrays are sort of applying the same spatial filter to everything, but I try hard to listen for that and am not able to identify it in any obvious, or at least negative, way.

[Gutbucket]

For those of you checking out the OMT array PDFs, you may have noticed that the only one fully circled with a red check mark was the OMT8 I'm currently using.  While I do think its the best one of the bunch overall, I may go back and circle/check a few other particularly useful setups.  I've not done yet that as its somewhat redundant with the circled red stars in the left margin already indicating which are generally best.  The red circle and check on that OMT8 array is something of a personal conceit!

There is to my mind a bit of tension in how many arrays to include for each channel count.  Good to keep it simple with only a few of each I think, yet also show and explain the logical progression and possibilities.  I tried to limit them to only those I feel are useful.  If a few more big red circles help home folks in more quickly on whichever ones may be appropriate for them instead of overwhelming them with too many options I'm all for it.

[mccordo]

Hey hey.  I've recently been working on revising the Illustrated OMT booklet PDF linked in my signature, long over due for an update.  Still working on addendum stuff: introduction & overview, channel assignments & file management, mixing, playback options, technical discussions, a brief history of OMT development, potential advanced arrangements, table of contents.. 

However, I think I have the setup section with diagrams of OMT3 through OMT8 setups pretty much nailed down. Attaching those here, pre-release, potentially still subject to final edits.  May roll most of these and a few others into a single document and replace the outdated version in my signature prior to getting everything completed.

Thanks, Lee. I’ve been following the OMT from afar for my any years and have had the opportunity to make a “standard” tape next to it a few times. This time I’ve downloaded the PDFs and will look into some other configurations based on this. This has really got me excited!

[fireonshakedwnstreet]

OMT6 is my base setup. The extra presence you get from the cumulative effect of the coincident and near-spaced directional mics really makes a difference. If you have actives or any of that kind of compact gear, it's a no-brainer. I do it with full size mics, except for the AT853 omnis.

[Gutbucket]

I’ve been following the OMT from afar for my any years and have had the opportunity to make a “standard” tape next to it a few times. This time I’ve downloaded the PDFs and will look into some other configurations based on this. This has really got me excited!

Fun times and looking forward to the next one! If you want to try this stuff and have questions, just let me know. Of course there is nothing wrong with a "standard" tape, especially if you know what you are doing, which you do.  This all adds complication, whether it's worth it is your call.

OMT6 is my base setup. The extra presence you get from the cumulative effect of the coincident and near-spaced directional mics really makes a difference. If you have actives or any of that kind of compact gear, it's a no-brainer. I do it with full size mics, except for the AT853 omnis.

Thanks for taking up the OMT6 addition of the wide-near-spaced pair, you are one of the first to do so.  In my mind, one of the significant changes reflected in the new PDFs is the elevation of that pair over the rear-facing microphones with regard to which channels should usually come first in the channel-count progression hierarchy of OMT6 and higher arrangements.  I've certainly not lost any love for the rear-facing channels, it's just that the wide-near-spaced pair addition is a more important fundamental contributor, used consistently every time.  The rear facing mics provide something lovely and valued, but more delicate and nuanced, more just-right seasoning than primary ingredient.

[EmRR]

Not sure if there's a better place for this, putting it here.   AB spaced pairs of omni and figure 8, to make virtual patterns, if needed.  The omni's have pressure build-up rings to increase upper mid sensitivity and treble directionality. 

Immediate need, grand piano in a big band setting with the drums right next to the piano.  Nulls of the 8's towards the drums.  Who knows what's gonna be best, but I have options.  Also feeding a PA, so gives FOH options too.  The omni's are already well proven for this job, never have drums been so close though. 

[rocksuitcase]

wow EmRR- nice. Would you mid telling us which mics these are? I can sort of guess from your sig line. but....

As to micing grand piano in a big band arrangement. I assume (at least for the FOH send) you have tried the somewhat typical fig 8 or cardioid under the lid positioned near the strings about 10" from the hammers?
One of my mentors used to put a 414 in fig 8 in that position.

I like the idea of pointing the nulls of the 8 toward the drums.  Thanks for sharing the picture and idea.     

[Gutbucket]

AB spaced pairs of omni and figure 8, to make virtual patterns, if needed.

Very cool. 

Attached is an appendix section I've been working on for the new OMT booklet revision, with potential advanced OMT arrangements, a number of which incorporate this kind of omni+fig8 combination at the wide spaced omni positions, providing post-process control over polar pattern in both front and rear facing directions.  In this way one can do things like derive different wide-spaced forward facing patterns, and simultaneously derive separate wide-spaced rear-facing pair patterns, while also retaining full low frequency omni extension.  Alternately one can use them more simply to to tailor the pattern in a single direction in the way EmRR is using them above, and thus the direct/reverberant pickup balance in the wide-spaced pair, controlling how much hall reverberance is included while retaining good wide-spaced reverberant decorrelation.  Might make for the ultimate OMT in that it provides much post-adjustability over the wide-spaced omniness.

When I added the ball attachments for the omnis, it was sort of a cheap/easy way of achieving some degree of this, yet with far less flexibility and no post-adjustability.

[Gutbucket]

I don't mean to speak for EmRR, but it appears, and I presume the omnis are Sennheiser MKH 20 and the fig-8's MKH 30. The pressure rings are interesting, acting similar to a ball attachment in their on-axis frequency effect. 

The following details won't matter for EmRR's application, but here are a few things I've realized in thinking about such omni+fig-8 "dial a pattern" combinations:

1) By inverting polarity of the fig-8, you point the derived virtual pattern the opposite direction. In the arrangement pictured above that would sound quite different from a forward facing pattern due to the omni facing the forward direction, a difference made even greater by the presence of the pressure ring.

2) That difference may be okay or even desirable depending on the application.  However, if identical front and rear-facing patterns are desired, either an omni small enough to be truly omnidirectional throughout the audible range would need to be used, or the omni could be oriented like the Mid of a M/S pair, facing outwards.  That would create forward/aft facing patterns that remain symmetrical to each other, yet balloon outward at high frequencies.

3) If a truly uniform virtual pattern shape across the entire frequency range is desired, both mics will need to have identical frequency response, frequency extension (and phase match).  Any differences between them in either category will alter the shape of the virtual polar pattern in that range.  The effect of the pressure ring will serve to make derived virtual pattern somewhat wider in the same range in which it effects frequency response, by providing a touch more omni signal than fig-8 signal in that range.  The effect of the typical roll-off in lowest frequency sensitivity of the fig-8 will cause the virtual pattern to grow wider and eventually transition to near omni at the lowest frequencies.  Senn MKH30 has a more extended low-frequency response than other 8's so it has some advantage there in maintaining pattern.. If that is what is needed.

4)Like Mid/Side, this can be used to advantage by intentionally equalizing the omni and fig-8 differently to alter the derived virtual polar pattern by frequency.

[EmRR]

Gutbucket ID’d the mics correctly.  I also had the treble boost on the omni’s, then counterintuitively shelved down the treble so the live mix was more omni-card range in the bass and more card-8 in the treble, with the on axis treble maximized before shelving it all down.

The 414 approach is normally what we do for FOH, I really prefer the AB approach for the capture/broadcast side if possible. This time we were out of space and inputs, so the 414 was dropped.

wow EmRR- nice. Would you mid telling us which mics these are? I can sort of guess from your sig line. but....

As to micing grand piano in a big band arrangement. I assume (at least for the FOH send) you have tried the somewhat typical fig 8 or cardioid under the lid positioned near the strings about 10" from the hammers?
One of my mentors used to put a 414 in fig 8 in that position.

I like the idea of pointing the nulls of the 8 toward the drums.  Thanks for sharing the picture and idea.   

[Gutbucket]

I also had the treble boost on the omni’s, then counterintuitively shelved down the treble so the live mix was more omni-card range in the bass and more card-8 in the treble, with the on axis treble maximized before shelving it all down.

Cool approach.  To clarify for everyone, to achieve the modification of polar pattern with frequency that EmRR describes (more omni-ish in the bass, more 8-ish in the treble) the high-shelf attenuation is applied to the omni prior to mixing with the 8.   Applying a high-shelf boost to the 8 instead would have the same effect with regards to pattern, yet would modify things the opposite way in terms of frequency balance.  This is the same as EQing the Mid and Side channels of a stereo pair differently.

Applying EQ to the combined output of both mics affects frequency only without affecting pattern.

Using the rings applies a sort of EQ preemphasis, which effects both tonality (more obviously) and pattern (because it does not boost the fig-8 by the same amount), which can be further enhanced or compensated for with the later EQs.  Where that EQ is placed in the signal chain is what determines if it will affect frequency balance only, or both frequency balance and pattern.