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Expand LCR to 5.0 Surround array
Old 1 week ago
  #1
Gear Maniac
 
TJP's Avatar
Expand LCR to 5.0 Surround array

Hi all.
Started Field recording a while ago. For most of the time I used a ORTF stereo setup for ambience recordings. Then I added a hypercardioid in between them (facing front side) as center channel inside a blimp and made myself a diy LCR setup. Now I would like to expand this existing array to a 5.0 surround array by adding two omnis as rear channels. In the future I want to build a 5.0 omni Williams Star array, but for now this combination of LCR + two onmis would be my only option. Is this a legit approach? And if yes, how should I position the rear channels to complement the LCR array (position, distance, angle) to get a nice surround ambience recording?
I know that the downside of this is that the recording can't be freely rotated in post, but I would just live with that limitation.

Hope somebody can help me with a clever solution of this tricky situation ^^
Old 1 week ago
  #2
My experience is that Williams-inspired "star" arrays function better on paper than they do in the hall. Many of them have really bad out-of-segment crosstalk, and I find the resulting conflict in localization cues quite bothersome. I've used a number of different surround arrays, but the method I keep coming back to when I'm in a hurry is OCT. For the surround channels, I either add rear-facing cardioids or a Hamasaki square -- sometimes both. I'm mostly not concerned about accurate rear localization or "critical linking" beyond the front triple. If you are, then Williams is worth another look, as are double M/S and full ambisonic techniques.

For a quick introduction look at this old brochure from Schoeps.

David L. Rick
Seventh String Recording
Old 1 week ago
  #3
Gear Maniac
 
TJP's Avatar
Thx for the excellent answer! The plan was to somehow build an (ideally spaced) surround rig, with the equipment that I own. Got a pair of MKH 8040ties, 8020ties, a 8050 a MKH 30, a 8070 and a 418s. The thing I want to try out is LCR + the rears as in an OCT. Im thinking of 40 cm to the LCR and a separation of 1-2 m (maybe with a slight outwards angle). This should generate enough signal separation and a nice image of the rear channels. My theory behind it is: ORTF is a mix of intensity and runtime stereophony. It has therefore a ok diffuse field correlation and an excellent image and localization. Adding a hypercardioid in the center makes the image more robust, adds more detail and makes the signal mono compatible. Arrays based on runtime or intensity have their pros and cons. Adding two spaced omnis as rear channels can sound quite nice, since imaging and localization isn't as high as in the front channels and you get a natural open sound with very little diffuse field correlation. Should I get too much crosstalk, I could attach barrie discs at the omnis effectively making them wide cardioids.... The other plan is to try out fig8 + spaced omnis in addition to the LCR.
Old 1 week ago
  #4
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i'm mostly not much concerned regarding pickup of rear surrounds and i have been using many different mics (from the usual suspects) in various ways (pretty close and therefore easy to handle to very widely spaced and therefore less easy to handle) and with almost every pattern (from shotguns to omnis), all of which i found to be useful in certain situations.

quite often i'm using a l/c/r system as mains and any pair of spaced mic's for surround recording; surrounds can be positioned on the sides of the stage or at the far end of the venue - what approach i'm using is mostly determined by the availabe setup time and the soundfield i'm aiming for. double m/s, double ortf and soundfield are very easy to deploy. depending on system, monitoring on location can be a bit more tricky though (due to necessity of decoding)...
Old 1 week ago
  #5
You can make a workable front triple out of two 8040's and an 8050. I would caution that it's difficult to design a good LCR array by simply guessing, but quite simple to do with a tool like Image Assistant.

The 8040's plus MKH30 will also make a fine double-MS rig. When working in a hall, I would suggest adding some decorrelated sound by using widely-spaced 8020's in the reverberant field. Be prepared to slide the latter forward or backward in time when mixing so they integrate well.

Few independent recordists own enough MKH30's to make a Hamasaki square, but it turns out that a "Hamasaki pair" is still useful. You can add a pair of widely-spaced omni's farther back and get much the same utility. Consider picking up a second MKH30 when the opportunity arises. (It will also let you do Blumlein stuff.)

David L. Rick
Seventh String Recording
Old 1 week ago
  #6
Lives for gear
 

forgot to mention something: to me, it makes a difference whether i'm solely relying on a surround mains mic system (and very few spots) or if i'm using multiple/lots of spots - for the latter, i prefer using a near coincident main mic system as alignment of spot mics is much easier and results in much better phase coherence between the mains and spots. for the former, more widely spaced system can be quite nice.
oth imo profit from very large rooms/halls; actually, i cannot remember a surround recording i did in a small(er) room which i really liked, no matter what technique and tweaking i used! on those occasions, i liked upmixing (with a little bit help of the studer vsp panning and a quantec surround reverb) better than 'true' surround mixing...

and on the topic of exanding from l/c/r to 5.0: most of my surround mixes heavily rely on the front mics, possibly up to 70 or 80% and only very rarely an ensemle/orchestra is into getting things mixed much differently: if so, it helps immensly to know about any preference or one risks to put mics in the wrong place...
also, don't forget about the lfe channel! i often but a blm or pzm behind the conductor; of course this is also helpful for 2.1 (or to record an organ) - much fun! i recommend using proper tools for alignment though.
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