Topic: Easy to understand reference for polar patterns X's distance for Newbs.....

[Brian Skalinder]

If I am 100' back from the stage, in a large venue, are you suggesting that I increase or decrease the angle of my microphones?

There's a thread in here somewhere on Stereophonic Recording Angle.  It should answer your question in detail, and far better than I could before I head off to work.

[intpseeker]

Thanks for the explanations and references. I know this discussion may plow old ground, but as a point 'n' shoot taper with forgiving equipment this is great stuff. +T's

[Will_S]

Gratephul, this may help too.
Depth and Dimension

This is a great resource for the discussion at hand andt also raises an important point about high frequency rolloff and perceived distance from the source.

So yes, based on recording angle arguments, you should actually use a wider angle between your microphones as you move back in the venue, to maintain the same perceived source width on playback.

But as you do so, high frequency response suffers based on both increased distance from the source and (for most mics) having the direct sound increasingly off axis, where high frequency response can suffer.  So if you just blindly pick a mic setup to match the stereo recording angle to the perceived angle between the PA stacks (or edges of the stage) from your location, you risk a pretty distant sounding recording IMO.

When it comes to amplified performances of the sort many of us tape, it seems to me like there's not a lot of stereo information in the music anyway.  That's why something like the Nutter/point at stacks approach works for a lot of people.  In this method you point your mics just outside the PA, and then since this usually means a reltively narrow angle betwen mics and this a tendency toward a mono recording, you then move the mics further apart to "compensate" by increasing the perceived spaciousness of the recording.  It's not an ideal approach in terms of angular distortion or a "correct" sterero representation of the event, but for the music there's usually not much stereo image to preserve IMO.   Of course if you can get good sound and set up in a spot where the point at stacks approach is equivalent to a traditional stereo setup like 20 cm and 90 degrees, you get the best of both worlds.  Still it's the crowd and room sound that's in accurate stereo rather than the music (in the sense of the position of each instrument being accurately reproduced).

I think it's good to keep in mind that a lot of stereo theory is developed for recording acoustic sources from fairly close up, when you really are trying to reproducd sound as coming from each individual performer in a distinct location in space.  When that's your goal, the information in discussions like these can be incredibly useful.  But for a lot of what a lot of us do, that really isn't the case much of the time.  So keep in mind what the stereo recording angle means for your image of the crowd and room sound, but also keep in mind what it's doing to the frequency balance of the PA sound.

[Gutbucket]

If I am 100' back from the stage, in a large venue, are you suggesting that I increase or decrease the angle of my microphones?

There's a thread in here somewhere on Stereophonic Recording Angle.  It should answer your question in detail, and far better than I could before I head off to work.

The counterintuitive relationship between the actual recording pickup angle vs. the angle between the mics has always been a tough one to get my mind around.

A Michael Williams paper, The Stereophonic Zoom, discusses this relationship and how to use it and vary it to your advantage.  This link is to the version hosted on the Rycote site, I believe it is also available as an AES preprint and supposedly is the first chapter of a book he's working on.  I emailed him a few years back when I came across the article to ask about the book and got word that it was not yet completed.  He basically extends the standard X/Y, ORTF, DIN, NOS conventions to a spectrum of position, pattern, and angle to achive any desired recording angle.

One thing I think about when trying to get a grasp on all this is that trying to reduce the chioce of mic setup to a simple correlation like "recording angle X with pattern Y and spacing Z yields recorded angle Q when played back over a standard stereo triangle", is that there are other aspects of the recording that may be are in my mind more important than a acurate placement of sources across the reproduced soundstage.  The balance between instruments, the overall frequency balance, the direct/diffuse ratio, the sound of the reverberation in the room, reflections off the side walls, the fact that we are often recording sounds emenating primarily through directional FOH cabinets on either side of the stage vs. independant sound sources distributed across a stage, the acuracy of the off-axis response of our mics, etc. all play a role and are usually more important to optimize than making sure the percussionist is reproduced in the correct position, IME.  I'm rambling, but what I'm getting at is, what was most benifitial to me in the paper was not using the technique he describes to achive recording angle X at distance Y from the source, but understanding the relationship between mic angle, pattern and spacing and the resulting stereo recording angle.

Looks like Will_S just addressed alot of the same ideas while I was typing, but I'll post anyway.

[Gutbucket]

Here's a DPA Stereo Recording pdf that describes the same relationship.  It's more of a 'how to' guide than a discussion of theory, but look for the graphs in each section that relate mic angle, spacing & pattern with the recorded angle and angular distortion.

[edited to fix link, thanks Will +T]

[Will_S]

Here's a DPA Stereo Recording pdf that describes the same relationship.  It's more of a 'how to' guide than a discussion of theory, but look for the graphs in each section that relate mic angle, spacing & pattern with the recorded angle and angular distortion.

Nice link, +T.  There is an extra period at the end of the link though (fixed in the quote above).

[RebelRebel]

an AES membership is a must , if only for the access to the vast library of documents alone..

[dean]

.

[gratefulphish]

Thanks DSatz, Teddy, Gutbucket and Will_S.  I will be reading all of the info.  +T to all for your contributions to my and others' education in this area.

[DSatz]

gratefulphish, sorry to be late in replying, but I had an opera to record last night (yeah, I know, "excuses, excuses").

The confusion, I think, is between two angles which have a cause-and-effect relationship, but aren't the same thing:

(a) the physical angle between the main axes of a pair of microphones, and

(b) the arc of sound from the original venue which they cover (specified as an angle).

The second of these is what Prof. Williams calls the "stereophonic recording angle," and in general, the wider you make (a), the narrower (b) will be and vice versa. That's the big paradox that I referred to earlier.

Most people assume that the wider they spread their microphones, the wider an arc they will cover. It's as obvious as the observation that the Sun revolves around the Earth ... and just as wrong. The arc that you cover with a stereo pair of microphones (coincident or closely spaced directional microphones, anyway) corresponds more or less to the area of overlap between their polar patterns. The wider you spread them apart, the smaller this area of overlap will be, and thus the narrower the angle of stereo coverage will be.

Whenever a direct sound source is picked up exclusively (or nearly so) by just one of the two microphones, it will appear to come from the location of the corresponding loudspeaker during playback. Usually you only want (at most) the very farthest extreme sound sources to be reproduced that way; often it's preferable for not even the most extreme left and right sound sources seem to come from the location of either loudspeaker. You don't want to "advertise" the loudspeaker's exact position, because stereo sound is an illusion and an auditory awareness of the loudspeaker position tends to spoil that illusion.

You want (this being an esthetic convention, i.e. something subjective that is nonetheless advisable because it's the generally accepted paradigm) the direct sound to be spread across "an appropriate amount" of the space between the loudspeakers, depending on how wide the original direct sound source was. A solo piccolo shouldn't fill the entire soundstage width, and actually neither should a solo piano, even if it's one of those huge, long Bösendorfer concert grands. Your choice of the microphone patterns and geometry (angle and distance between mikes, and distance from mikes to sound sources) determines the audibly "apparent" width (what the Germans call the "stereo basis width") that will be produced later over loudspeakers.

--best regards

[Gutbucket]

...Most people assume that the wider they spread their microphones, the wider an arc they will cover. It's as obvious as the observation that the Sun revolves around the Earth ... and just as wrong. The arc that you cover with a stereo pair of microphones (coincident or closely spaced directional microphones, anyway) corresponds more or less to the area of overlap between their polar patterns. The wider you spread them apart, the smaller this area of overlap will be, and thus the narrower the angle of stereo coverage will be...

Sometimes it takes a bit of talkin' until the essence is distilled.  There it is.  Well put.