Topic: The Myth of Microphone Reach by Shure

[Gutbucket]

Another common myth: The '3:1 Rule' apples to recording with a stereo pair of omnis.

It does not, and would actually be impossible to implement that way or nearly so.

[Gutbucket]

Common TS myth: Omnis behave omnidirectionally when worn on your person.

I hear what you're saying but don't agree.  The mic is still "behaving" exactly the same.  It's just that the sound reaching it is more directional.

I came across some back-up on this while browsing TS today, from a source more credible than myself-

..body-mounted microphones can't possibly function as omnis at mid or particularly at high frequencies..

Here's the full post from the recent 'anyone using omnis exclusively?' thread- http://taperssection.com/index.php?topic=150689.msg1918573#msg1918573

[John Willett]

First of all I agree... there is no such thing as "reach", it's just a perception.

But AT has some diagrams for AT853 capsules which show exactly how much reach they have.  It shows some ratios where cards have a reach of 1, omnis are 0.7, hypers are 1.2, and the miniguns are 1.7 (those figures are from my memory).  If a manufacturer publishes those, it propagates the myth.

These are directivity ratios, but I have never seen them quoted as you have them.

An omni is 1.0
A cardioid is 1.7
A super-cardioid is 1.9
A hyper-cardioid is 2.0
A short-gun is 2.2

This means that a cardioid at 17cm distance will pick up the same sound as an omni at 10cm.

It also means that a short gun (like a 416) will pick up at 2.2m what an omni does at 1m - so a short gun will only just over double the distance compared to an omni.  (and a mini on-camera gun is more like a hyper-cardioid than a gun mic. and even shorter).

It's nothing to do with "reaching out", it's the directivity ratio based on the polar-pattern and the fact that the more directional patterns pick up less reflected sound.

[Gutbucket]

More specifically, those directivity ratios indicate the difference in sensitivity to sound ariving on-axis verses sensitivity to sound arriving from in all other directions. I think those ratios are misleading when converted to actual distance measurements, because that variable aspect will be different in different rooms.  In normal spaces there is more direct sound in proportion to diffuse sound closer to the sound source, but how quickly that changes with distance depends on the environment.  And because it changes with environment, and also with distance within each environment it makes those comparitive distance numbers misleading. For example- in an anechoic chamber, the effective difference between on-axis sound and off-axis sound is identical for all microphone patterns, simply because there is no off-axis sound arriving at all.  That is not a typical recording scenario of course, but emphasises the point that in addition to the the directivity ratio of the microphone, the environment in which it is used also determines how various patterns will behave at various distances.