Question On The 3:1 Theory

[bradjacob]

The theory of 3:1 states that for every unit of measure the mics are awayf from the source, they should be 3 units of measure away from each other.

For overheads, where does the source get measured FROM? The toms are lower that the cymbals, and the snare lower that the toms.

Is it simply a case of using a happy-medium? For example, using the toms as the point of source (since the snare is lower and cymbals are higher)...

What does everyone do in this situation?
_________________
- Brad
www.GhostsOfTheParting.com
www.MapleLaneRecording.com

[locosoundman]

The three to one rule applies to spot mic'ing - e.g. if you have a trumpet player and a saxophone player in the same room, and you put a microphone on each instrument, the saxophone player should be much closer to his mic than he is to the trumpet mic and vice versa. When mic'ing up a drum kit, this would apply to the individual drum mic's - the diaphragm of the snare mic should be at least 3x closer to the snare than it is to the high hat.

With overheads, you are dealing with a different scenario. Rather than trying to pick up a single instrument with a single mic, you are generally trying to pick up multiple instruments with (usually) a pair of mic's. The two mic's are acting more like your ears - they are working together as an array to reproduce the sound of the drum kit. 3:1 does not apply here. In this case, you are placing the mic's in such a way that you will pick up a blend of the overall kit. Rather than thinking of each drum individually, you are mic'ing the entire drum kit as a single instrument (sort of).
_________________
"We have met the enemy and he is us"
- Pogo Possum

[subatomic pieces]

[the finger genius]

[farview]

The 3 to 1 rule does not apply to stereo micing techniques.

The 3 to 1 rule is about isolation. The most common use for it is when there are multiple instruments playing in the same room, each with their own mic. Like the trumpet player and the sax player in the last post, the sax player needs to be three times farther away from the trumpet mic than the trumpet player is, otherwise you will end up with phase cancelation due to bleed.

Which brings us to another source of confusion about the 3 to 1 rule: Phase. The 3 to 1 rule can make it easier to avoid phase problems, but only because it isolates one mic from the other. It's the isolation (the lack of bleed) that keeps the phase problems in check, not because it's some magic point in space where all the frequencies become time-aligned. (that can't happen)

As long as the two mics are at equal gain (not equal volume) the signal coming out of the distant mic will be 9db lower than the close mic. That difference in volume makes the phase cancellation (which is still there, by the way) so quiet that it isn't a problem.

However, if you match the volume of the close and distant mics, you will have all the phase problems you would expect.
_________________
Jay Walsh
Farview Recording

[locosoundman]

To be even more precise, the 3:1 rule (guideline, theory, whatever) applies to multiple sound sources with the same intensity level (more or less). It wouldn't help you much if you were trying to record an mbira in the same room as a Marshall stack.

[rhythm ranch]

[Professor]

Well said by everyone.

I like to teach it as the "Greater than 3 to 1 recommendation" because of all the confusion that seems to surround how it is usually taught.


I'll also toss in the notion that as a ratio it is reversible, meaning that the distance between two mics can be the "1" and the distance from the mics to the source can be the "3". That helps make sense of something like an ORTF pair over a drumset.


-Jeremy

[rhythm ranch]

Excellent point (as usual) Jeremy.

[rwc]

what makes more snese to me is having the mics not pick up the same thing. the 3 to 1 rule is one way of not having mics pick up the same thing, but it confuses people who ask "then how does ortf/XY work?", Unless you want to use phase fuckups to your advantage, which is something I wouldn't recommend to anyone who hasn't already made great, phase coherent, interesting recordings, I say fuck this rule, and go for what sounds good, and try to keep a stereo pair from picking up the same thing. get to know your mic's pickup pattern, and how it hears things. Get to know how it hears things in conjunction with the other mic you are using for a stereo pair, whether it is matched or not. instead of aiming to obey the 3 to 1 rule, aim to do what the 3 to 1 rule is trying to get you to do in the first place.. keep you from pointing two mics at the same shit from different places.

the 3 to 1 rule exists to keep you from having mics pick up the same shit and cancel out, like a spaced pair 20 feet over a piano that are pointing down, parallel, that are 3 feet apart. but you can do this with mics right next to each other far from a source.. like blumlein, or xy, or ortf.. so fuck this rule!

like when newscasters get close together and you can't hear them as well.

there's also a sick world of sonic creativity between phase coherency and total mess that creates larger than life sounds and stereo fields you'll never get from adding reverb, panning, or standing in the room.

but, you can also dig a miserable hole for yourself when stuff sounds like cock and balls. this is why listening to what you are doing is important when you are doing some retarded bullshit to get a sound you want. do not satisfy yourself with being impressed by the fact that shit works and you hear something faintly resembling a drumset, or a choir, or a piano while recording. Do not satisfy yourself with the fact that musicians aren't walking out on you because of your perceived incompetence. Do not fear that musicians will get pissed off at you taking time to dial in a sound, because it's them who will ream your ass for the rest of your life to everyone they meet when their record sounds like unrefined crap!

do not stop moving shit, swapping shit, hacking away in the daw/console until you have something that sounds like what you have in your head. and if you have nothing in your head, get something in your head that sounds like a finished record by listening to everything you can, from every genre, on as many stereos as you can, for the rest of your life.

it's your trip.. have fun.

I've been drinking since 11 AM. time for sleep.
_________________
Real friends stab you in the front.

Oscar Wilde

Failed audio engineer & pro studio tech turned affordable modern gizmo repairman and tech for various studios along Manhattan's grimy 30th street.

[mwingerski]

[rwc]

[MoreSpaceEcho]

[roscoenyc]

like the Proff said 3:1 is a suggestion.

main places I use it...


1. If I've got a band playing open (w acoustic and or amps) together in the room I'll measure the OH to Snare and set up the band that distance X 3 around the drums probably with some go-bo's too. This same thing works well for a live vocal in the room (especially with a mic like the M-500 positioned null towards the drums)
Also good distance for room mic.

2. multiple mics on a guitar cabinet
_________________
http://www.cowboytechnical.com/
http://ericambel.com/

[farview]