difficult question - phase issues

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elan
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difficult question - phase issues

Post by elan » Wed Mar 11, 2009 2:50 pm

hello

i've recorded a bass from a svt cl.. and i've reamped some tracks, electronics drums.. etc.. i've putted the mics in a strange position.. near the opposite angle of a big room.

because i liked how it sounds, there was a lot of "boing" and long decay on the kicks and everything, but in a pleasant way.

now i've checked all, i like the effect, but i have some big anti-phase in some points, in some notes..

i've panned the two tracks, and aligned, than moved with the track delay to find a sweet spot.

but i still have some anti-phase, i think they are cool, because the bass (synth bass) is always very big and this creates some "imperfection" some "movement" some space, specially a more 3d sound.

but, there are ways to solve this problem?
or do you think that mixing, equing, the problem goes away?

thanks

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Post by Scodiddly » Wed Mar 11, 2009 3:34 pm

Hmm... room mode standing waves that end up out of phase with the direct (or even reamped) wave?

Not sure how you'd get rid of those, though. Maybe try filtering out narrow notches around the room mode frequencies?

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Post by Professor » Wed Mar 11, 2009 3:58 pm

OK, that kind of phasing is caused by the delay of the sound traveling across the room before arriving at the microphone. And the cure for that is indeed the delay that you have already setup on the track and adjusted to your favorite spot.
But you still have some bits that are out of phase...
And that's the whole idea.
Part of why you like the sound of that microphone placement is because of what is going on in the room. And what is going on in the room is more than just the sound racing across the space from the amp to the microphone. That same sound energy is also bouncing off of the floors, and the walls, and the ceiling, and the bookshelves, and empty beer cans, and whatever else is in there before arriving at the microphone a little later than the "direct" sound. That's the part of the phasing that you want. That's the good stuff. That's why it sounds like a room

So the easier answer is, don't sweat it.
You have done exactly what you need to do to preserve the impact and power of the original signal, and the extra stuff you are seeing are just the juicy tidbits that you were looking for when you stuck the mic on the other side of the room.

That's not to say that more severe phasing wouldn't be a problem, or that more phasing translates into more spaciousness. But a big part of spaciousness is parts of the sound bouncing around and arriving late.

-Jeremy

elan
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Post by elan » Wed Mar 11, 2009 7:02 pm

Professor wrote:OK, that kind of phasing is caused by the delay of the sound traveling across the room before arriving at the microphone. And the cure for that is indeed the delay that you have already setup on the track and adjusted to your favorite spot.
But you still have some bits that are out of phase...
And that's the whole idea.
Part of why you like the sound of that microphone placement is because of what is going on in the room. And what is going on in the room is more than just the sound racing across the space from the amp to the microphone. That same sound energy is also bouncing off of the floors, and the walls, and the ceiling, and the bookshelves, and empty beer cans, and whatever else is in there before arriving at the microphone a little later than the "direct" sound. That's the part of the phasing that you want. That's the good stuff. That's why it sounds like a room

So the easier answer is, don't sweat it.
You have done exactly what you need to do to preserve the impact and power of the original signal, and the extra stuff you are seeing are just the juicy tidbits that you were looking for when you stuck the mic on the other side of the room.

That's not to say that more severe phasing wouldn't be a problem, or that more phasing translates into more spaciousness. But a big part of spaciousness is parts of the sound bouncing around and arriving late.

-Jeremy
thanks professor, you are the kind of professor i wish i had in all the schools i went.

btw, the room is a big room, something like 12 meters to 5.. or something like that, all the ceiling is wood, solid wood, not painted with anything, and the floor is moquette.. and the sides are cork. i like how the room sounds, even if it isn't treated with bass traps.. so there are points in the corners where some freq resonates a lot!! and the amp is on one short side, while the mics are one (re20) in the corner but near the amp, at the same level of the upper speaker pointed to the other corner, and in the other corner at 12 meters more or less, there is an oktava 319 modded :P) pointed to the re20..

i think is pretty strange.. but i like how the lows resonates here, and also some mid highs in the oktava..

the oktava is more mid, mid/highs, and some ambient noise, the re20 is much darker and deeper, so i have the left lower and the right higher (in frequencies)

in some points of the song, are not a lot at the first glance, say that one note is a lot more in the left and the second note is all on the right (i'm talking about the lows, not the rest)

so, at the first glance seems good in that way, i like it, but i like to receive suggestion about how to manage that, i mean if i have to be careful in some things.. or if i can improve also the mono in some way.

i mean maybe i'm worrying too much about that, as you say, but is the first time i face that kind of situation, and in the past i've done some mess with the phase.. i mean going in a big studio to check it the kick wasn't so solid and even the bass was strange.

but this time seems all ok :) for now.

i have to be very careful because all instruments are 3/4 or even more tracks..are all synths..

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Post by ashcat_lt » Wed Mar 11, 2009 7:29 pm

I'm not completely convinced that it's a phase issue so much as "simple" acoustics. Like, if you were actually standing where the mics are, you'd hear the same thing. Some frequencies are stronger at the one point then the other. Do you get the same effect with the direct tracks muted?

In any case, you could try some "bass management". You can roll your own by sending both mics to a mono low pass filter, and then hi-passing the channels themselves. If you're ITB, there are a number of plugins which will do automatically to a single stereo bus.

If it is a phase issue, you could try delaying it more. Rather than sliding toward the direct sound, slide back later, so that the delayed material correlates less to the direct. This will sound like an echo, rather than a comb filter.

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Post by elan » Wed Mar 11, 2009 7:55 pm

well i can't try that now, but i think that if i mute the mono tracks i haven't that effect, i mean it changes in some way.

i have 5 bass track, one is the ITB track of the soft synth (and is panned C), another is the direct of a re20 (C) another is a oktava at 1.5 mt than i've done another reamp.. and is the one with the re20 and the oktava in the corners.

so the first three mics are all in the center.. while the two in the angles are L-R

the point is that the rest of the song seems solid, there are just some points where the lows oscillates.. but is still solid, but has also that effect..

i don't know if can compromise the mix..

maybe tomorrow if i can i post something

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Post by jesse_baccus » Sun Mar 22, 2009 11:35 am

another excellent response by the professor!

i will add, that there isn't a 'cure' for phase, only band-aids- in a pinch where a mic was placed very poorly in a room on a guitar amp, i have had success with multi-band upward expansion. but it still doesn't 'fix' it, only makes it less troublesome when the other program material is summed with it across the mix bus.

phase is how we hear depth and dimension, and is not a bad thing. the ridges on our outer ear create phase discrepancies which allow us to tell where a sound is coming from. the same thing goes for working within a soundstage on a mix. if you like the way it sounds then don't worry about, unless your gut is telling you its a serious problem.

all rooms have nodes, anti-nodes, and modes- which define a rooms characteristics, based on the rooms fundamental resonance. it sounds to me like the mic was in a null point at the frequency of the notes which are disappearing. This is the same reason why when recording bass guitar some notes will really BOOM and others wont, and is a matter of positioning and room treatment (balance and control).

if you are working digitally, sliding the waveforms so that their envelops are moving together (similar to the delay technique), will help make the discrepancies sound more intentional and solid. Because yes, the if the bass has phase issues, and you try to balance a kick in with it, both will change and loose impact.

It sounds like you're on the right track, and thinking, so keep experimenting and you'll lock it in!
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Post by Waltz Mastering » Sun Mar 22, 2009 5:22 pm

It's fairly easy to tell if something is out of phase. Sum the two sources to mono, if the low end diminishes or the track sounds thinner it's out of phase. If two sources are 180 degrees out of phase they will cancel out completely.

You can fix it by reversing the phase on one of the channels. Some plugs and most consoles have that feature. You can also move the wave form by samples until the waveforms are in phase. The company that makes the re-amp also make a box called phazer. There probably a couple more fixes as well.

TW

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Post by jesse_baccus » Mon Mar 23, 2009 11:19 am

Waltz Mastering wrote:It's fairly easy to tell if something is out of phase. Sum the two sources to mono, if the low end diminishes or the track sounds thinner it's out of phase. If two sources are 180 degrees out of phase they will cancel out completely.

You can fix it by reversing the phase on one of the channels. Some plugs and most consoles have that feature.
TW
ahh!!! this from a mastering engineer???

what TW is referring to switches the electrical POLARITY, and has little to do with acoustical PHASE. if the two signals are a perfect 180* out and envelopes resemble one another, switching the polarity can help a bit, but phase is far more complex than making negative propagation positive, and vise versa.

for example, i got a record in to mix from an engineer who used the blumlein technique on an acoustic guitar upon my suggestion that had never done it before, and accidentally placed one of the two mics facing backwards. the problem was immediately apparent, and by switching the polarity of the backwards capsule allowed the track to be usable. it wasn't fixed, but it was usable.
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Post by MoreSpaceEcho » Mon Mar 23, 2009 12:41 pm

jesse_baccus wrote:ahh!!! this from a mastering engineer???
WTF?

new guy. you sure talk a lot.

you know, the board didn't just spring into existence with your arrival two days ago. many of us have been here for years and we have in fact discussed the difference between "polarity" and "phase" many, many times in the past. i'm pretty sure we all understood what mr waltz meant.

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Post by jesse_baccus » Mon Mar 23, 2009 1:20 pm

MoreSpaceEcho wrote:
jesse_baccus wrote:ahh!!! this from a mastering engineer???
WTF?

new guy. you sure talk a lot.
pardon me for contributing.
you know, the board didn't just spring into existence with your arrival two days ago. many of us have been here for years and we have in fact discussed the difference between "polarity" and "phase" many, many times in the past. i'm pretty sure we all understood what mr waltz meant.
one should say what they mean, make records not assumptions. if its been covered thoroughly then why do i hear the mistake so much? on boards and in real life. who's to say everyone reading that post has read these other discussions? the reader will still take the wording as fact, and continue spreading misinformation.

phase-v-polarity is a pet peeve of mine, i don't feel i was aggressive or condescending, and i expect an equal level of stickler-ness from you in keeping my posts accurate for other readers (so i do appreciate you checking me). quality control.

my exclamation was in jest, a fact which tom is aware of through private messaging.
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Post by ashcat_lt » Mon Mar 23, 2009 8:29 pm

Yeah, there's a lot of confusion in the real world re: phase vs polarity, and the statement in question was posed in such a way as to be very misleading.

I'm kind of sick of typing and reading about the difference myself, but there are newbies and random googlers coming through here all the time. I find it best to clarify these matters for their benefit, not mr MoreSpaceEcho (or most any of the regulars, for that matter).

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Post by MoreSpaceEcho » Mon Mar 23, 2009 9:41 pm

sorry...being an old curmudgeon on a Grumpy Monday..don't mind me.


mr MoreSpaceEcho is my dad.

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