Topic: Oddball microphone technique (OMT) - part 3

[Gutbucket]

Sure glad I played with LEGO's as a kid.

Totally LEGO-licious!  Chuckling at the hall-of-fame-grade assembly complexity displayed in the above photo.

Cool that you were able to manage the wider spread.  Do you feel that aspect translates in a significantly differently way in the mix?

[EmRR]

Cool that you were able to manage the wider spread.  Do you feel that aspect translates in a significantly differently way in the mix?

I can't tell that it does in this case.  Fairly shallow wide room with long decay time, more ambient than it should be for a loud show.  Stand position is offset from center, so the most significant thing I notice is the change in lopsidedness related to the closer PA stack, which isn't a big deal in the overall mix, the AB being significantly down in the mix for reasonable bass contribution.  In this case I am low-passing the AB at 6dB/oct at 3kHz.

[EmRR]

OK, comparing the standard Manfrotto bar width to this, this sounds definitely wider, maybe too wide for my taste in this room.  Sounds good on speakers, really wide on headphones.  I may make a V shape with AB back some to get a width in between next time.   

The Ambisonic array winds up 71º angle with the most shotgun like pattern available in the Rode Soundfield plug.  The KMR81 is also in the middle, down 12-15dB, and band-passed to lose the hard treble sparkle and bottom.  Lots of early reflections to fight in this room.  AB is down -15 relative to the ambisonic mic levels before they hit the encoder.

[Gutbucket]

Sounds good on speakers, really wide on headphones.  I may make a V shape with AB back some to get a width in between next time.

Over the years I think I've sort of trained myself to target "slightly overwide, yet acceptably so" when assessing using headphones with speakers in mind.. sort of shooting to split the difference in an attempt to satisfy both.  Maybe I've now internalized that as sounding "correct".

I probably posted here not that long ago about recently using a forward angled 'V' AB config, due to the constraint of how I had the near-spaced L/R supercard pair mounted to the telescopic antenna AB arms in my rig.  I'd originally set it up so those supercards were at a near +/- 90 degree arrangement (ala Theil's OCT L/C/R) whenever I used the BAS Shure windscreens on them, even though I arranged it so that I could angle them slightly more forward than that even with the arms in-line pointing straight out to the sides. After deciding that I wanted to modify their angles to +/- 45 degrees even when recording outdoors, I achieved that by temporarily by angling both telescopic arms forward enough to get the L/R supercards to +/-45 degrees. That shifted them slightly forward somewhat in relation to the center M/S pair and pushed the omnis at the ends of the arms much farther forward.  Although those changes weren't desirable (I prefer them in-line, and would rather push the omnis backwards if necessary), I didn't find significant negative impact from dong so, and significantly preferred the more forward angled L/R supercard pair.

A few weeks ago I finally re-worked the way the BAS Shures are supported on the arms before recording at a local outdoor amphitheater so that they now achieve +/-45 degrees with the arms straight out to the sides.  I didn't get good photos of that but I may record at another local amphitheater this weekend and if so I'll be sure to snap a few.

[heathen]

Question for the OMT experts.  I'm finally getting around to working on my JRAD Red Rocks recording from last summer.  I ran DPA 4061s spread as wide as I could...at least 15 feet I'd say.  Going into the show I was planning on sticking with just that but for the hell of it I took a patch from Todd R's MG M200 rig that was set up in the center of the "section" (and thus about the center of my DPAs).  I figured I could use those sweet sweet MGs to fill in the center of the DPAs if needed.

When I started mixing them together, though, the stereo image got weird at times.  It's most noticeable on a guitar solo, where it will sound like it starts to come from one side then shifts to the other side (left/right in the stereo image, that is).  I kept track of which mics were in which channel so I'm pretty confident I don't have the L/R channels mixed up.  I did try swapping the channels of one set of mics and that seriously messed things up so I don't think that's the issue.  Todd's mics were in a near-spaced configuration...I think it was approximately DIN.

Does anyone have an idea about what could be going on here?

[rocksuitcase]

Question for the OMT experts.  I'm finally getting around to working on my JRAD Red Rocks recording from last summer.  I ran DPA 4061s spread as wide as I could...at least 15 feet I'd say.  Going into the show I was planning on sticking with just that but for the hell of it I took a patch from Todd R's MG M200 rig that was set up in the center of the "section" (and thus about the center of my DPAs).  I figured I could use those sweet sweet MGs to fill in the center of the DPAs if needed.

When I started mixing them together, though, the stereo image got weird at times.  It's most noticeable on a guitar solo, where it will sound like it starts to come from one side then shifts to the other side (left/right in the stereo image, that is).  I kept track of which mics were in which channel so I'm pretty confident I don't have the L/R channels mixed up.  I did try swapping the channels of one set of mics and that seriously messed things up so I don't think that's the issue.  Todd's mics were in a near-spaced configuration...I think it was approximately DIN.

Does anyone have an idea about what could be going on here?

Not sure what is going on without listening, BUT, in your case I have done a gutbucket technique of "monoing" the coincident stereo pair for centered imaging but leaving the omnis to provide the stereo cues.

[EmRR]

I might play with MS processing on the center pair to see if it gives any clues.  The other thing would be to try moving the center and AB pairs apart by 6dB, see if it images better with one more predominate. 

[Gutbucket]

It's most noticeable on a guitar solo, where it will sound like it starts to come from one side then shifts to the other side (left/right in the stereo image, that is).

To establish a starting point for the discussion, does each source (wide DPAs, near-spaced MGs) behave the same or differently with regards to this particular guitar panning phenomenon when listened to in isolation?

[Gutbucket]

Didn't end up recording this weekend, but snapped a few photos in the parking lot yesterday while starting rework on the rig, currently in process.  Latest changes are the repositioned L/R big Shure windscreens to angle that pair ~ +/-45° when the main arms are +/-90° in-line with each other.  Note the holes in the front of them, through which the antenna arms formerly passed, angling that pair ~ +/-75-80°.

Other changes are the addition of a gaff-wrapped bent-coat-hanger support-wire to help support the rear-facing pair (similar to what I've long used to help support the main arms), and the addition of the hinged AT mic-clip for the center M/S pair, which was rigidly mounted previously, making for easy vertical angle adjustment which helps point up at PA somewhat and reduce the pickup of audience in the center as well as making for more compact rig stowage without disassembly with the mic folded down so as to be nestled in with and parallel to the others.

You may note the extra, currently unused stubby XLR up there, which I'll probably eliminate. 

I'm thinking of adding a flexible vibration isolation assembly between the center hub and stud which mounts to the stand, extension, or clamp, shock-isolating the entire assembly.  I'll need to determine the right stiffness for that to work effectively: flexible enough to reduce transmission of noise through the the stand or clamp, yet stiff enough to not wobble excessively.  They exist to isolate entire Decca trees and the like, but if I rework the center hub to which the antennas attach I may build something which incorporates some thick Sorbathane I have on hand.

[EmRR]

Looks great

[rocksuitcase]

Nice looking changes. I especially like how it all folds up and looks like a gang of Big Ass Shures! 

[Gutbucket]

Thanks. With all five Big Ass Shures in place and without the center mic being able to fold down I couldn't fully close the 30" x ~7" diameter padded bag I had been using, and was just toting it around half zipped.   The rig fit nicely in that bag using the smaller indoor-only windscreens everywhere except the center M/S pair, but I decided its too much hassle and stress on the wiring and windscreens to switch regularly back and forth to the BAS, so I decided to leave the BAS on basically all the time unless I'm in a situation where a smaller visual impact is especially important.  I searched to find a more appropriate sized bag and ended up with the Neewer photo gear bag.  Overall its slightly larger than necessary and than I'd prefer, but of everything I came across this was closest to the dimensions required. The big stand lays across the top of the bag and secures in place with two integral clip/cinch straps.  If not using the big stand I can fit clamps, telescopic extension bar and folding tripod foot in the main compartment, which can be somewhat compartmentalized using 3 provided velcro-placeable dividers.

The F8, TallentCell battery and peripheral recording stuff fits in the padded front pocket and I plan to cut a pass through into the main compartment for the cable snake.
 
The DPAs all use Naiant PFAs plugged directly into the recorder except the center supercard which uses a DPA phantom adapter which up to this point I had mounted aloft directly behind the mic at the hub.  I've had it set up that way ever since I transitioned from a single rear-facing mic to a pair.  I'm now rearranging things to move the DPA adapter down to the recorder along with the PFAs by using a CD-Int female-microdot>male-microdot extension cable, which explains the extra XLR up top which is now unused.. thinking I may leave it up there to facilitate experimentation with alternate center microphones.

The Naiant PFAs terminate in pairs to mini-xlr plugs to which the snake to the mics attach.  The strips of gaff-tape on those and on the PFAs themselves identify which is which, by feel in the dark if necessary.

[prepschoolalumniblues]

I have a MixPre-3 but have only used it with a stereo pair. This week, I picked up a Manfrotto 154 triple mic bar (65cm wide, or just over 2 feet) and a handy-dandy custom three-channel XLR cable from Ted, so I’m really excited to try out a new approach.

Here’s what I’m currently thinking: I’d like to try wide-spaced subcardioids (using the full width of the bar, 2 feet) with a hyper in the center. I typically record amplified music indoors in small, not-great-sounding, weirdly-shaped rooms. My thinking is that by using subcards I’m taking the more “standard” OMT approach of spaced omnis and making it slightly more directional to compensate for a limited footprint (I would have a hard time going beyond 2 feet wide in the rooms I record in) and the room acoustics. The hyper would provide center clarity and help avoid any perceived hole in the middle.

Am I off-track here? Any thoughts on angling the subcards versus having them point straight ahead like an A-B omni pair? (Should I just go with an omni pair?)

[Gutbucket]

I'd give it a go initially with the supercardioid in the center facing directly forward and the spaced-subcardioid pair angled ~ +/-45 degrees.. then experiment further from that as starting point.  If in a bad room, it may help to angle them so that they are directly PAS, even if that means they are angled less than +/-45 degrees, and you might consider switching the subcards to a more directional pattern like cardioids or supercards.  Outdoors you might want to angle the subcardioids wider, up to +/-90 degrees, as their response should remain well-behaved far off-axis.  That may seem extreme, yet it represents a ~12" spacing / 90 degree inclusive angle between the center microphone and each microphone to either side, akin to two standard 2-ch stereo DIN configs placed adjacent to each other. 

[prepschoolalumniblues]

Thanks! I'll report back once I have a chance to try it out...

I'd give it a go initially with the supercardioid in the center facing directly forward and the spaced-subcardioid pair angled ~ +/-45 degrees.. then experiment further from that as starting point.  If in a bad room, it may help to angle them so that they are directly PAS, even if that means they are angled less than +/-45 degrees, and you might consider switching the subcards to a more directional pattern like cardioids or supercards.  Outdoors you might want to angle the subcardioids wider, up to +/-90 degrees, as their response should remain well-behaved far off-axis.  That may seem extreme, yet it represents a ~12" spacing / 90 degree inclusive angle between the center microphone and each microphone to either side, akin to two standard 2-ch stereo DIN configs placed adjacent to each other.