phase cancellation question

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kawika
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2018/01/02 22:36:50 (permalink)

phase cancellation question

Re: live drums
My overheads  (in phase with each other and toms) are out of phase with my snare. I noticed 2 solutions both of which appear to yield same results, but I wondered about conventional wisdom (oxymoron?).
 
1) Print out of phase and reverse (or nudge, or use relevant software) afterwards.
 
or
 
2) reverse polarity before tracking and print in phase.
 
thanks

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    Cactus Music
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    Re: phase cancellation question 2018/01/02 23:41:28 (permalink)
    Sorry I'm not good at totally understanding exactly what I SHOULD do so I just flip the phase and use which ever setting sounds the LOUDEST. Not very scientific eh.. 

    Johnny V  
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    #2
    LLyons
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    Re: phase cancellation question 2018/01/03 00:33:41 (permalink)
    Live tracking - now that takes time to learn.  First - to me, its all about mic placement, even one inch makes a difference. As I am setting up, I try to record a bit, then listen AND look at the phase relationship in the waveform - so I print with any phase reversal.   It used to take hours to get it right,  now - it takes less than a few hours to get a really successful placement. 
     
    I used to nudge after, a LOT, to get the tracks to phase align but I do this a lot less now.   It doesn't sound full and like standing in the original room listening to the take. Sometimes I have to nudge to fix afterwards, like when I rush a setup, and the audience is already coming in the door.
     
    What helps me equally, is to ISOLATE all the other mics on the kit from the snare, like toms, high hat, even bass drum.  The less snare in these mics help a bunch, at least to my ears - and gates are my friend for live work.    

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    kawika
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    Re: phase cancellation question 2018/01/03 02:29:26 (permalink)
    Thanks for the info. Just wondered about pros/cons of printing vs changing at mix down. Yea, I noticed engaging the phase on my interface printed the reversal including the new visual waves. I also noticed that Sonar reversed the phase afterward but did not direct it to print during tracking.
     
    thanks
    #4
    bitflipper
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    Re: phase cancellation question 2018/01/03 16:00:21 (permalink)
    There is no difference, other than getting phase sorted out prior to tracking saves the additional step of having to correct it later.


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    ooblecaboodle
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    Re: phase cancellation question 2018/01/03 16:41:37 (permalink)
    they're probably not completely "out of phase" - as in, phase-flipped. It's more likely that they're not time aligned. 
    The snare mic is far far closer to the sound source than the overheads, so the snare hit arrives at the close mic before it does on the overhead microphone(/s).
     
    You can either tweak the location of the mics a bit until you find a good compromise, or use the appliance of science, by delaying the snare channel so that it perfectly lines up with the overheads (or, slip the overheads earlier so that they line up with the snare).
    This technique is used almost always when recording classical performances in large venues, and I'm not entirely sure why it's not "the done thing" with drum kits. I tried it many years back, and found that it really adds a solid low-mid BANG! to the snare, so I stuck with it.
     
    I find that it can help the toms cut through a bit as well, but in my drum room, there's insufficient low-end from the bassdrum being picked up to cause any issues, so the bassdrum doesn't cause much concern. Time-aligning it can add a more defined attack to the bassdrum sound, however.

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    Cactus Music
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    Re: phase cancellation question 2018/01/03 17:36:31 (permalink)
    I always record bands I play in just for fun and make an 18 track recording. Because the board didn't have direct outs or spare Aux sends I would just use extra mikes direct to my interface.  I was using 2 SDC's in front of the kit at about 3' hi. Very pleased with the results. 
     
    I also would record the stereo out from the board via the USB. I guess because of the differance in latency between the Tascam us1641 and the Yamaha mixer ( WDM mode) it would instantly make the drums, vocals or guitars go dead when you pulled the Yamaha board tracks up in the mix. Flipping the phase on  the Yamaha mixer track brought it right back. 
    It's one reason I like to use as few mikes on the drums as possible. Unless you have either a tried and true set up, or all day to fuss about, drums are tricky. I keep forgeting that rule... 3:1 right? 
     

    Johnny V  
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    #7
    fret_man
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    Re: phase cancellation question 2018/01/03 19:54:53 (permalink)
    Once the mic picks up the sound it makes no difference if the polarity is toggled during or after tracking. However, mic placement will affect the phase shift (time delay) seen at the various mics compared to the other mics. For example, the snare picked up by the overheads will be delayed compared to the snare mic. Flipping the polarity will not change this.
     
    A good rule-of-thumb is to remember the speed of sound is about 1msec/ft. If the overheads are 2ft away, then they will see a 2msec delay. This corresponds to a half cycle of 250Hz, which is where you'll see a notch in the frequency response (or peak when you flip the polarity of the snare mic). 
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    kawika
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    Re: phase cancellation question 2018/01/04 09:15:13 (permalink)
    Thanks guys!!
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    Anderton
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    Re: phase cancellation question 2018/01/04 09:48:12 (permalink)
    Cactus Music
    Sorry I'm not good at totally understanding exactly what I SHOULD do so I just flip the phase and use which ever setting sounds the LOUDEST. Not very scientific eh.. 



     But good advice nonetheless 

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    #10
    GreenwoodStudios
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    Re: phase cancellation question 2018/01/04 09:59:12 (permalink)
    IMHO fixing phase issues first is the optimum choice because especially for drums chances are you are sending various levels of these drum inputs to a reverb (vst or hardware) via an aux send, which is heard on the stereo bus so having those in phase mics in phase is best rather than waiting to address it later.
    #11
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