hobbyist wrote:My preference is for multiple arrays. It offers more flexibility to make the final mix. And it reinforces some learning when you can hear the differences each gave for the same exact set up.
Fair enough, and I certainly agree with the educational aspect of this approach. Presumably, though, the intended aim of learning the character of different arrays in different positions is to be able, eventually, to select the right array and locate it in the right place to achieve the required result first time?
Just for clarity, my background is in live broadcast where a multi-array approach is often not practical (or acceptable). Instead, it is generally desirable to minimise the rig and derig times as well as system complexity, which means employing the simplest mic setup possible to get the job done, and placing those mics in the appropriate positions from the outset to achieve the required balance and perspectives. This was why I was interested to better understand your 'computations' ... But I realise now we were at cross purposes.
Acoustic width seems more important to me.
Fair enough. I think we'll need to agree to disagree on that. For me the most critical qualities of a recording by far are the instrumental balance and the acoustic perspective -- by which I mean the contribution of room acoustic (reverb) against the direct sound. And these properties apply equally as much to a mono recording as a stereo one (or a surround one). These are determined almost entirely by the physical position of the mic/array. Acheiving a satisfactory stereo spread Is trivial by comparison, and is easily done by manipulating the mic array mechanically or electrically after the desired perspective is found. ...in my experience and practice, anyway.
...you often are constrained where the mikes can be put so worrying about the room is less important within reason. My experience is that acoustic perspective is good if you are close enough. Or even at the back of the room like I had to do once as it was the only location available.
We obviously have different experience and priorities -- which is not a criticism, just an observation.
That critical distance is something to avoid.
To avoid it, you have to know what it is -- either by measurement, calculation, or imperical experience. But the point I was making was that if it is known, it is possible to calculate the optimum distances for mics/arrays of different polar patterns, and from that where to place a specific stereo array for good results.
And for anyone unfamiliar with the term, the Critical Distance (Dc) is the distance from a sound source where the sound pressure level of the (directional) direct sound is equal to the level of the reverberant sound. The critical distance is large for a dead room, and short for a very reverberant one. Space or ambient (room) mics are placed beyond the Dc value, while the main pickup mics must be inside the Dc value -- the precise amount determined by the polar pattern(s) and desired wet/dry balance.
The computing of the width is to avoid problems. Doing it first simplifies everything.
Odd... It seems quite the reverse to me!
And of course you must keep in mind room acoustics so as to not make a bad choice of distance for the stereo part but pick a bad location for practical recording.
Ah yes... I think this is where I came in! :-D