Quick spaced pair question.

[DrewPeterson7]

Hmm... I feel like I've read about the 3:1 rule pertaining to a spaced pair on a single source in a few books, and heard it mentioned in a few video tutorials. I'll have to investigate further. I do appreciate everyone's professional responses to my question when it's obvious I'm a greenhorn. Yeah, on the kick mic.

Glen's right- I've seen it a ton of places too, first I think in an article on micing acoustics that cited the rule as a reason to make sure a spaced pair (say, one on the 12th fret and the other on the soundboard) were at least 3x the distance from each other as they were from the source.

While that may (or may not - it's been forever since I've mic'd up exactly like that, since my guitar (and technique) seems to work pretty well with an X-Y setup) be good advice and I certainly believed that to be the 3:1 rule when I first joined here, I've since been (politely but persuasively) informed I was incorrect.


EDIT - of course, what you call it matters absolutely nil - as long as you're getting good-sounding, in phase recordings, you can call it the "Alan Jackson with a head full of acid, counting backwards from 20" spacing technique, and while it'll make for some interesting online debate, ultimately it's the recorded results that matter.

 

[SouthSIDE Glen]

Yeah...but is it organically grown?

I don't know; do hydroponics count as "organic"?

G.

 

[moresound]

I don't know; do hydroponics count as "organic"?

G.

As long as there is plenty of horse sh!t on it............ I think it's a good qualification.

 

[miroslav]

As long as there is plenty of horse sh!t on it...:

There's plenty to go around!

 

[moresound]

Yes there is....... but be sure not to step in it!

 

[mshilarious]

A fundamental principle of spaced pairs (or even near-coincident pairs) is that there is a phase difference; that's part of (or in the case of spaced omnis, nearly all of) the difference in the channels that creates the stereo image. And the same is true with our ears; they are spaced too. Our brain is an extremely sophisticated processor, so when it sums these two sources we hear it as spatial information rather than phase cancellation.

But it's important that the left/right signals not be electrically (or digitally) summed before being broadcast back to our speakers, otherwise all our brains will decipher is a source with no spatial information and a lot of phase cancellation.

This is why coincident mic techniques are said to be "mono-compatible", because no phase cancellation occurs if the signals are summed. If mono compatibility is important, don't select a spaced pair (although many techniques involve more than two mics, partially to mitigate that problem).

Back on the topic of spaced pairs and the 3:1 rule. The 3:1 rule is primarily useful in live sound (where multiple sources WILL be summed to a single channel), although it does have application in the studio as well, for example if you are recording an ensemble live with close mics and wish to preserve isolation between instruments. A critical presumption of 3:1 is that there is no source in between the two desired sources. That's untrue for virtually every stereo recording situation, whether it be a piano or an orchestra. Obeying 3:1 in that case will always create a "hole in the middle"; adding a center mic to mitigate that will violate the 3:1 rule.

In conclusion, if you obey 3:1 in stereo micing, you will have a mono-compatible two-channel signal that is worthless as a stereo recording.