Mics far apart - phase adj in post

R

RecNewbie

New member
Hi,
I've recorded a string orchestra concert in a small auditorium.
There were a couple of pieces with soloists, and I used an NT2A for accents.
I was forced to put my Zoom H4n in the stage direction platform, quite far from the stage, for security reasons (every other place it would have been in the path to the emergency exits so no dice).

Now I'm listening to the recording and can't seem to gel the accent mic with the general stereo recording... guess I have to delay it by some amount.
Is there a way, preferably in Reaper, even with a plugin, to see a phase cancellation diagram for two tracks and decide how much to delay it?

Or do I just do some math based on a distance of let's say 15m, an optimal position of let's say 4m from the other mic, and thus repositioning the audio tracks roughly 11/340 = 32ms apart (is the math even correct)?
(Edit: I've just tried moving the Rode track 0.032s forward and it sounds quite better, maybe it's just placebo effect?)

Newbie, so please correct my reasoning if wrong in any (or all) part(s) :)
Thanks a lot in advance
 
I'll use the math to get it close then use my ear to make it sound right. Or I'll skip the math and get it close by eye.

One trick is to use precedence effect. Match the level of the solo instrument in the near mic and the far mic, pan them hard to opposite sides, then slide the far mic on the timeline until it sounds centered. If they're level matched you can often hear a subtle panning effect where the first arrival sounds more present. This works best in headphones.

Another trick is to listen to the phase effect. Match the levels of the solo instrument, pan them both center, then slide the far mic until it sounds most clear. A variation on this is the invert the polarity of the far mic and slide it until you get the most level drop, then invert it back.
 
I think if you hold down alt, and click within an item, you can slide the actual audio without moving the item itself, basically setting the start time offset for the underlying audio.

Doing it by eye is almost always quicker and easier than doing math, even if it's simple math. Find a part of the recording where it's just the soloist, zoom so you can see both waveforms with some detail, alt-drag one til the squiggles match as closely as possible. Then listen and slide it around til it sounds right to you.
 
RedNewie I didn't get your math example(?
bouldersoundguy said:
I'll use the math to get it close then use my ear to make it sound right. Or I'll skip the math and get it close by eye.

One trick is to use precedence effect. Match the level of the solo instrument in the near mic and the far mic, pan them hard to opposite sides, then slide the far mic on the timeline until it sounds centered. If they're level matched you can often hear a subtle panning effect where the first arrival sounds more present. This works best in headphones.

Another trick is to listen to the phase effect. Match the levels of the solo instrument, pan them both center, then slide the far mic until it sounds most clear. A variation on this is the invert the polarity of the far mic and slide it until you get the most level drop, then invert it back.
Click to expand...
That's an interesting approach, I wouldn't have thought of. 'Pan shift via precedence is potent and it's in full effect in less than a millisecond difference in arrival. I wonder how it would fair with the close+far combo's differences? Maybe go with one far one close at a time first?

Another is visual align on the sharpest transient you can find.
 
Thanks all... I tried different delays and was satisfied with around 55ms for the mic nearer to the soloists.

@mixsit sharp transients are a rare thing in this recording... bowed instruments only, no percussions, no pianos, no pizzicato etc.

@ashcat can't rep+ you yet
 
Good.. progress :>)
For fun, went back to your math example. 15 - 4M. I solved in feet, ;) but 8M - 29MS.
Back again ...scratch that I totally screwed some simple math :facepalm:
11M 36' 32MS
Once I started... "I gots to know.. :>)
 
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mixsit said:
The distance of interest -for this exercise is the distance of near to far mic.
Click to expand...

I was calculating a resulting distance of about 5m because among the few things I know (or I think I know :P ) about mic placement is that 3-1 rule... so I was trying not to get the two mics too close, albeit "virtually".

I had a plan of the venue, but there is no scale on that plan, so it's pure guesswork...
 
RecNewbie said:
I was calculating a resulting distance of about 5m because among the few things I know (or I think I know :P ) about mic placement is that 3-1 rule... so I was trying not to get the two mics too close, albeit "virtually".

I had a plan of the venue, but there is no scale on that plan, so it's pure guesswork...
Click to expand...

The 3:1 rule of thumb (a guideline, not a real rule) is for multiple mics on multiple sources (like close mics on a drum kit), not for multiple mics on a single source (like a soloist with a close mic and a far mic).
 
bouldersoundguy said:
If the near mic is on the path to the far mic it's the same thing. If the near mic is placed off the line to the far mic then it's what I said above.
Click to expand...
I know you know your stuff' I'm just trying to get my thick head around what you were saying. :)
Let's see if this helps (me.. grins

.... Far mic.....time/distance to be compensated.....Near mic.....Instrument
Same relative mic setup, but the instruments back some
.... Far mic..........same compensation..................Near mic.............Instrument
 
mixsit said:
I know you know your stuff' I'm just trying to get my thick head around what you were saying. :)
Let's see if this helps (me.. grins

.... Far mic.....time/distance to be compensated.....Near mic.....Instrument
Same relative mic setup, but the instruments back some
.... Far mic..........same compensation..................Near mic.............Instrument
Click to expand...

Think of it like this, far mic in front of source at 15 meters. Option 1, near mic 1 meter from source, directly in line with far mic. Option 2, near mic 1 meter from source, above source, 90° off the line to far mic. Different mic-to-mic distances, but same compensation, time equivalent to 14 meters.
 
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bouldersoundguy said:
Think of it like this, far mic in front of source at 15 meters. Option 1, near mic 1 meter from source, directly in line with far mic. Option 2, near mic 1 meter from source, above source, 90° off the line to far mic. Difference mic-to-mic distances, but same compensation, time equivalent to 14 meters.
Click to expand...
Thank BSG. Now... I go back and read what you said the first time it makes perfect sense. Sometimes I'm just thick :)
 
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