searching for an explanation of phase

erichenryus

erichenryus

New member
OK. I understand what phase is in a mathematical sense (I majored in physics) so I'm not looking for a webster version or anything like that. I'm just looking for some good online information about phase problems, how to hear them, how to avoid them, how to correct them, and....how to understand what the hell i'm looking at with the phase scope.

Specifically, I've been recording acoustic lately with two mics and noticed that it sounds very cool in a headphone sort of way but I also noticed that when I summed the two channels to mono the track disappeared! I think that's a bad thing but it also seems to me that phase difference in two channels also conveys spatial information so what do you do about this and why is it bad that the mono signal cancelled itself?

Anyone have links to anything I can read or have any real knowledge to share on this topic?
 
yes i did a search and it didn't turn up much that i could sink my teeth into. maybe i missed something?

i actually just did a similar search at recording.org and got a lot more of what i was looking for.

i'm now thinking that a lot of my phase cancellation is due to the fact that i'm using two different preamps for the mics.
 
The preamps shouldn't make a difference. The main issue is that sound from the same source is hitting two mics at different times. It is this difference in distance and time that causes comb filtering and phase cancellation.

There is a rule called the 3-1 rule that can help minimize phase problems. The distance between a second mic should be at least 3x the distance from the first mic as the first mic is from the sound source.

One of the big challenges now is that what causes phase problems in mono mixes can actually be beneficial when the mix is run through a Dolby Surround decoder. So now you have to worry about perfect phase relationships causing mono tracks to sound great but then a DSS box will stick it all in the middle speaker, lol. There's a good middle ground there somewhere and I'm trying to understand it better myself.
 
TexRoadkill said:
So now you have to worry about perfect phase relationships causing mono tracks to sound great but then a DSS box will stick it all in the middle speaker, lol.
Click to expand...

That's kind of what I'm wondering about. I'm panning the tracks hard left and right and it sounds very cool (note, I'm not an audio engineer so I'm thinking what sounds cool to me might not sound cool to someone who knows what they are doing) and I assume that I want some phase difference between the two to create some depth to the track but I also assume that I don't want the track to dissappear when I step back from the speakers and it gets blended together (which it isn't). I'm confused.

When I run both tracks mono I'm definitely getting some serious filtering but the mics are pretty much the same distance from the guitar. I'll try the 3/1 technique.
 
erichenryus said:

When I run both tracks mono I'm definitely getting some serious filtering but the mics are pretty much the same distance from the guitar. I'll try the 3/1 technique.
Click to expand...

In addition to the 3/1 technique try delaying one (or more) of the tracks until the samples align more closely. You would be surprised at the difference this makes on drum tracks particularly between the overheads and the rest of the kit.
 
THIS is probably the best thread I have partaken in on the topic. Should help.


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