Topic: 3 mic (LCR) distance

[Chanher]

Best sounding might be just two channels.. or six, or whatever.  Too many variables to predict best sounding, and a lot of it is how you set things up and how you use whatever you've got.  Mostly I think using more than two microphone channels can help to stack the deck in your favor, making it more likely you can produce a great sounding recording given all the real-world constraints under which tapers record.

I wanted to note an experience this weekend that applies to anyone thinking of adding more mics or currently doing it. I showed up early to a local jazz jam, hoping to get some good 3-4 mic onstage action. Due to multiple circumstances I made the smart decision to ditch all the new gear and just run a simple stereo setup in the sweet spot of the room. Very glad I did. I could just tell the onstage mix would be skewed; they mic'd the quieter instruments through a small PA so out in the room would get the best mix of all instruments and thus the best recording. Ended up with an excellent recording that is very listenable.

My point is don't be afraid to master the art of 2-mic stereo recording as well. I thought of doing 3-mic LCR in the audience, with the center channel picking up some sweet sound direct from the stage, but 2 discrete mics just felt better than a larger 3 mic setup as I was right in front of the majority of the viewing audience. Real-world constraints. I ran at853rx cards PAS straight into the XLR's of the warm mod pmd661 and I couldn't be more pleased.

Side note I'm getting fatigued with the at853 hyper capsules, I think I'm gonna save them for the shittiest of venues and/or extra chatty situations. This is my first time using the warm mod 661 and I think it is just as smooth but more detailed than the mp2. I personally find these mods to be subtle yet still adding pleasing frequency bumps in the right areas. They (usually) make raw files more listenable, skipping tedious post work IMHO. I can't wait to try the CM4's into it.

Also that Schoeps app is VERY cool.

[Gutbucket]

-I should definitely mention that even though I had the center mono hyper ~1 inch AHEAD of the CM4's (as recommended), I ended up visually lining up snare hits on ALL sources/feeds. I did some quick listening to the 3 mic mix with the center mic left alone and then with it visually aligned (the actual difference was miniscule) and if I'm being honest I didn't hear any difference so I left it lined up. I know Gutbucket talked about moving the center mic forward more in relation to the distance of the outside (left right) stereo pair and perhaps in future recordings I can experiment with that.

Saturday I installed smaller Movo windscreens in place of the big Shures in my recording rig for a day of recording Sunday. While doing that I was checking the 3-microphone L/C/R portion of the array against what is suggested by the Schoeps Visual Assistant for this combination of pattern, spacing and angle.  In it, playing around with the center forward spacing mostly affects how correctly the imaging links up between the L/C and C/R segments of the array.  I found that given the pattern, spacing and angle I'm using between the L/R microphones (supercards, 24" [61cm], 45 degrees), Visual Assistant suggests more center forward spacing than the ~6.5" I am using currently.  Alternately or in combination with that, I could push L/R farther apart and/or angle them wider.  Shifting L/R a bit farther apart is what I think I'll do when I rewire everything at some point, as that's when I have the opportunity to adjust wire-lengths and move things around more freely.  The current L/R spacing was originally setup for use with a wider L/R angle, but I found I like the L/R pair more on-axis with the PA so I now angle them +/-45 degrees, and should increase the spacing to compensate for that change in angle.  Ideally I'd like to figure out a way to easily adjust the angle of the L/R pair to anything between, say, +/-30 deg and +/-90 deg when setting up in the field, then adjust spacing to fit the angle.  Would be super slick to build the bar-clamp mechanism in such a way that things are mechanically linked, so the angle would change simultaneously as spacing is adjusted, and all incorrect combinations are automatically avoided, but that's more mechanical complication than necessary.

The only 3-mic arrangements in Visual Assistant that work with no center spacing at all are super-wide arrangements of omnis (typically) in a line. For relatively-narrow arrangements with L/R spacings closer to that of typical 2-channel near-spaced arrangements, the only solution via Visual Assistant is to push the center microphone position much farther forward, something like 1 to 2 meters or more (in plan view the LCR triangle becomes very tall with a narrow base, rather than wide at the base with relatively minimal height), which then requires the application of delay or manual time-position shifting of the center signal in the DAW such that an impulse from the stage is time-aligned across all three channels.  That's not a practical taper arrangement at all though, as front back spacing is usually more difficult to achieve in taper situations than left/right spacing.

As mentioned earlier in this or in another thread, if free to adjust pattern, spacing and angle, the sweet spot for tapers with regard to forward spacing of the center microphone position might be to use whatever arrangement achieves good image linking while placing the baseline of the L/C pair perpendicular to a line to the left PA stack,  and vice-versa for the C/R pair and the right PA stack.  Sort of PAS with regard to the each baseline on either side of center.  That should optimize imaging as well as transient arrival from each stack to each side.  It will also tend to produce a triangle arrangement that is significantly wider at the base (L/R) with relatively minimal forward spacing of the center.

[Chanher]

My very crude visual depiction of gutbuckets “triangle” explanation of how to place the forward Center mic in an 3-mic LCR arrangement. As I understand it, you want to make an imaginary triangle (math people plz tell us the type of triangle) with the Left mic, Center mic, and left PA speaker, and then a second triangle with the Right mic, Center mic, and right PA speaker. I plan on trying this the next chance I get.

Please correct or add anything.

[Gutbucket]

Yes, that's what I'm proposing as a reasonable, relatively easy to apply rule of thumb that aims to get time-alignment right natively without needing to do anything in the DAW, while also achieving about the right forward-center spacing needed for good image linking.

[Gutbucket]

Below is a screen-shot of the L/C/R microphone arrangement currently comprising the center portion of in my rig, simulated in Image Assistant after measuring it up last weekend.  The angle of the L/R microphones in the rig are currently constrained to +/-45 degrees.  From the Image Assistant curves it appears this arrangement would benefit from a bit more center forward spacing so as to achieve optimal image linking.

So in the second image, I've shifted the center mic 5cm farther forward, which visually improves linking in the graph, but also widens the SRA a slightly by doing so.

BTW, it sounds good as is, without using any time alignment - and the forward spacing is pretty close to achieving the geometric alignment Chanher and I discuss above.