is a phase problem sonically obvious?

[sadworld]

how would i tell if i had a phase problem.... is it possible i've already had this problem and didn't even know it? it's probably difficult to describe in words but what should i be listening for? thanks....

[entropy]

hey sadworld

yes, it is sonically obvious. out of phase speakers give me a headache in no time at all but i guess it depends on what's out of phase. in a monitoring setup, an out of phase tweeter is (to an untrained ear) pretty hard to spot as opposed to a whole monitor being out of phase. and certainly, phase cancellation between mics on a drum or guitar setup can be difficult to hear if you don't know what you're looking for.

what to look for? the most obvious sign is bottom end punch and definition disappearing, the top end? i can only define it as having a "swish" (for want of a better word) and a smearing. the easy way (if it's a source) is to isolate the sound (yes, use the solo button if you want) and monitor it in mono. is it changing/ thinning/disappearing? if so, chances are it's out of phase. Try using the phase button on you're console, does it make a difference for better or worse?

Just back to the "what to listen for"? If it's 180 degress out, it just makes me feel queasy/nauseous. grudge

hope that helps

[Clueless]

It can be very obvious. I had a pair of outboard EQs feeding a mixer and due to a routing error, I had the same signals going both to the console and the outboard EQs. Strangely, I notice that as I bought up the outboard EQs, the sound level decreased. I traced the problem to phase error. This in turn led me to contact the EQ vendor, since it wasn't a phase wiring problem on my side. They confirmed that, lo and behold, in all the years nobody had reported this phase problem with their EQ units before.

Fortunately the fix was trivial: I changed an internal jumper from "Pin 2 Hot" to "Pin 3 Hot" and the phase error was fixed.

[natpub]

it can be very obvious. figure it this way, if you get a long enough time seperation in two identical instances of a signal, we can call it chorus, flanging, or phase shifting :-)

[LTA]

Originally posted by mdbeh
If you have multi-miced drums, overheads plus close mics, etc., listen for anything that sounds muffled or out-of-focus, like a snare that, instead of clearly cracking, has a sort of 'whoosh' around it.

Also, the "untrained" ear has a far easier time picking out the effects of the change in comb filtering, rather than the effect itself. Move one mic towards or away from a farther away mic, and the effect should jump right out at you (like flanging). Once you know what to listen for, it gets easier hearing it.

If you can't hear it with drum mics right away, try it with a nice distorted guitar using a close and distant mic pair.

Or, if you are speaking of monitors, throw up a center-panned track and sit in the monitor sweetspot. If the sound is apparently coming from anywhere other than dead center (as in, off to the sides or even "behind" you), one of your monitors is out of phase with the other. Might as well check the polarity of your speakers too. A positive waveform should make your woofers come out towards the listening position. Be creative, make a low-frequency wave form and cut off the second half of the cycle. Pull off your speaker covers and watch the woofer move when you play back, noting the direction. Reverse polarity of the wiring to fix the issue.

[sadworld]

sorry. yes, i was talking about micing drums and other instruments.... thanks.

[5down1up]

simple way to start ( still takes 3 people ) set up a snare and 2 mics . do one close mic and a room mic . flip the phase on the room mic and carry it around till you get a real " tiny " sound .
then flip the phase and listen .

maybe that helps ?

[PTMixer]

Originally posted by sadworld
how would i tell if i had a phase problem.... is it possible i've already had this problem and didn't even know it? it's probably difficult to describe in words but what should i be listening for? thanks....

the sound will disappear when you combine left and right channels

[mdbeh]

Originally posted by PTMixer
the sound will disappear when you combine left and right channels

For the situation he's asking about--multiple mics on drums, etc--that'll never happen in practice. The sound will only disappear completely if the channels are identical, and phase is then flipped on one of them.

If you're combining signals from different mics in different places--like overheads and kick drum--there will be phase cancellations, but it'll amost never be as dramatic as sound/no-sound. It's more the lack of bass, punch, clarity, etc. that have already been described on this thread. Using 5down1up's method, you can sometimes get the out-of-phase signal _close_ to gone, but you'll still hear something.

[5down1up]

yep , you will still hear something ... thats why its so hard to explain !

maybe you start with 2 mics and make sure they have "excatly " the same distance form ONE soundsource ( like a snare drum ) .
so the signal needs the same amount of time to get to both microphones .
in fact of we are living in a 3D world you can imagine how many possibilities there are . ( of course most are useless , some are good )

i suck in mathematics so maybe someone who knows that stuff for real JUMPS IN !

[djui5]

The best way to understand what phasing does is to flip the phase of one of the master buss channels (L or R) and listen...that's the most dramatic way to hear what's going on.


When you mic up a drum kit there's really no way to keep everyting "exactly in phase". That would suck anyways...a lot of what makes a nice stereo sound is slight phase differences between one speaker and another.

Another good way to hear phase cancellation is to solo a bass track and duplicate it...then nudge one copy a little bit untill it starts to sound weird and the volume decreases....the more you move it the more it will start to come back.

Phasing is a difference in time a waveform arrives at your ears and you have to have more than one source for phase to occur. You can't solo a single snare and hear phase cancellation.

Then there's the 3-1 rule...for every 3 feet you move away from the source you should have the mic's 1 foot apart for proper phase coheriency. Though different frequencies will change this formula a little....it won't work the same for a bass cab as it will for the ride cymball....

[LTA]

Originally posted by 5down1up
i suck in mathematics so maybe someone who knows that stuff for real JUMPS IN !

The math in the end is unimportant. Microphones are basically just physical embodiments of conic sections. Inverse square law and the relationship between distance and time are simple algebraic interactions. Then there is the empirical 3:1 rule.

Oddly, it is something you can learn to visualize without the math, just by using some simple tools such as a few mini-mag flashlights, a tape measure, a length of string, and some rudimentary concept of geometry. I'd love to explain this one more, but a simple 5 minute demonstration would translate into pages of text that wouldn't make sense without a bunch of pictures of something difficult to capture on film (or with a ccd).

You'd be surprised at how few most correct choices there are for any one single given circumstance. It is VERY similar to framing a shot with a camera. Sometimes you want a telephoto lense, sometimes you want a wide-angle one. And yet other times, you are so close to the source you need to pull out the macro feature. Ever seen 2 cameras on a single stand being used to create stereo cards? Or how about this?