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Are we micing drums wrong with common techniques?

Discussion in 'Drums' started by jscott, Nov 30, 2001.

  1. jscott

    jscott Guest

    There's a concept at work out there, that if you think about it, makes some sense. At least to me it does.

    For speakers, you want the excursion of the woofer to be outward with the thump of say a kick drum (in phase). And then of course theres all the argument for time alignment, etc. To accomplish this, the diaphragm of the mic needs to be pushed in as the wave hits the mic. Given most mic the kick from the inside of the batter, this is almost a given to occur. Well, consider what happens as you hit the snare, or toms, and at what direction the mic is facing. The wave of the hit of the drum is thought to be 180 degrees out due to the movement of the head by the stick. So the argument is being made that in fact all mics placed in the downward position on drums should actually be phase reversed electrically. Now before someone jumps all over me and says, no you're doing it wrong, I'm not doing anything other than rasing this topic for discussion, or the merits of...

    This argument to me makes sense because to my ear, as a drummer, I prefer the tone of the kick miced from the outside of the batter head when other mics are facing down at the heads. The whole of the kit seems to be more even. Although from a time alignment perspective, I wonder if the whole kit is not out of align by a degree? If you don’t change the overhead phase, then when micing the kick from the inside or out front (assuming nothing else has changed) would result in an out of phase condition for the kick. I got to thinking about this because of a comment I made about the May internal mic system and the need to reverse phase if you have mics on the inside of the toms/snare facing the batter head. It may actually be that to the contrary, only the mics on the outside (such as overheads) may need to be reversed (of course it depends upon where placed and direction facing. But lets assume for the argument, the overheads are on top facing doen towards the batter heads).

    I have read that it is common practice for some to reverse phase of the overheads to gain more warmth and depth out of them when used either on their own, or when in combination with close mics. And in practice, I have found that to be the case. It seems that when overheads are used on their own, reversing the phase electrically would explain why the warmth and depth comes out if in fact they are now truly in phase, giving credence to the concept. However, if the overheads are used in combination with the close mics, and the close mics have no reversal, yet the overheads do, its possible its just a cumulative effect of a phase at a given frequency, which explains why it can be touchy to place mics overhead.

    Has anyone experienced this? Thoughts?
     
  2. pan

    pan Guest

    are you talking about absolute phase?
     
  3. jscott

    jscott Guest

    Originally posted by pan:
    are you talking about absolute phase?

    Well, I believe I am, but I could also be wrong on that issue? I am always willing to be educated.
     
  4. RecorderMan

    RecorderMan Distinguished Member

    Joined:
    Mar 28, 2001
    1. there is no such thing as absolute phase. You mean absolute polarity. While phase is the measurment of an angle (remember trig?) and as such can be 0 degrees, 180 degrees, 45 degrees, 270 degrees , ect... Absolute polarity can either be in or out. period. This happens by "flipping the phase" i.e. switchin pin 2 and pin three of your mic cable, or the equivalent, of any piece of gear that let's you do it.
    2. All other phase that we speak of when speaking of busing or otherwise combining multiple microphones together is known as RELATIVE PHASE.
    3. Buy a phase polarity checker. You know...that litle gizmo that comes in two boxes. One makes and asychronous clicking sound...the other one is the reciever.
    4. Since the kick is the lowest fundumental source in the kit and probably the most affected by relative phase, make sure the kick mic is in absolute polarity. This will mean that a positive waveform applied to the mic from the kick will reproduce a positive excursion from your speakers (as opposed to "sucking in");thereby making a fat,punchy kick.
    5. NOW. USE YOUR EARS. all other mics placed can now be checked(by flippng phase on the micpre,module,ect) so that the RELATIVE POLARITY SOUNDS BEST TO YOUR EARS( btw I'm only capitalizing to make key points stand out-I am not neing rude)

    6. Over heads can go "in or out" of relative phase, with themselsves and against other mic's (kick,snare,toms...etc). Height above the floor can be played with to achievew a spot where the relative phase is pleasing.

    7. If you try the OH mic placement I gave on the OVERHEADS thread this will stop being an issue because they'll then be in relative phase with the kick and snare.

    There is always a null at some frequency between any two or more mic's. All you can do is pick that freq. by adjusting the positions and polarities of the mics, so that the null is high enough, so as not to be a problem.

    Happy phasing
     
  5. Kev

    Kev Well-Known Member

    Joined:
    Nov 13, 2001
    Interesting topic!

    Go back .... way back ... at a time when all this was just getting started. The BBC, Telefunken, Paul Klipsch, James Bullough Martini(Lansing), Ken Decker etc....

    Anyway rather than bore you with a long essay full of mistakes because I can't be bothered to get out of my chair, there was a convention with Microphone and speaker makers but it seems to have gone???

    Take a JBL woofer and a 1.5 volt battery. Connect positive to the red and negative to the black on the speaker and you may find the cone moves into the basket. Your other speakers like RCF may move out from the basket.

    It is not so easy to do simple tests on Microphones but I believe that most hold to the same convention but beware there are some that have a different idea.

    Any way the point is ... the early convention was , if you push the diaphram then the speaker would go into the basket which is the reverse to what you suggested so you can see how the convention has got messed up. In the PA business it might make more sense to to have FOH the other way round and this is usualy the case BUT the monitors are often reversed to FOH if you align the monitor across the front of the stage with FOH near by.

    Is any of this making sense??? I'll shut up now.
     
  6. jscott

    jscott Guest

    Originally posted by Kev:
    [QB]Interesting topic!

    Any way the point is ... the early convention was , if you push the diaphram then the speaker would go into the basket which is the reverse to what you suggested QB]

    I need a clarification on your comment. Are you saying that due to polarity issues, that when the siaphram of the mic is in an inward motion, the excursion of the speaker is also being sucked into the basket? I remeber the battery thing from a long time ago. But taking off on Recorderman's discussion, wouldn't it also stand to reason that in fact, at some distance away from the head, either direction of excursion is possible due to relative phase?

    The discussion was not so much of an " I need to know how to tell phase" as much as it is a theoretical topic that I am trying to get a better handle on. I mean, how many reverse phase for the kick drum when placed inside pointed at the beater? If all the other mics in a close miced situation are acceptable picking up the sound of the stick with the head moving in a outward motion, why wouldn't the kick be captured in reverse phase with the mic aimed at the beater?
     
  7. Kev

    Kev Well-Known Member

    Joined:
    Nov 13, 2001
    quote:

    "how many reverse phase for the kick drum when placed inside pointed at the beater?"

    I have a friend who does this when working with his PA system.... everytime I've tried this I end up with the system howling so I have to back the normal .... ie reversed.

    As far as recording I just hit the phase swithces until I'm satisfied with the results - then record. I have tried to think about it logically but have concluded that there was too much going on with phasing between toms and HiHat bleed that getting scientific just didn't help.

    As far as the comment on the distance away from the head, either direction of excursion is possible due to relative phase?

    Low frequency can have a very long wavelength and it depends on how low you are concerned with. I think 30Hz is 16 feet .... it's late and I could be wrong. Anyway the point is , inside the kick drum is a very small place with respect to the fundamental for the drum.
     
  8. sixpence

    sixpence Guest

    I think I mentioned something about that here a while ago.
    It was a concept of Jay Graydon's(producer for Al Jarreau and a few others). It makes sense to me from an absolute polarity point of view. However the actual phase at the mic depends completely on frequency and distance.
    Comb filtering occurs when 2 mics (or more) pick up the same source at different distances away. Obviously some frequenies will be out of phase (relative to each other) at the mic. it only really matters at lower freqs because the ear can't distinguish CF at higher freqs (the dips in response are too close together).
    Practically I'm trying reverse phase on all downward pointing mics to see if it makes a difference. funnily enough I noticed some older samples i made have a negative phase starting waveform when viewed in soundforge(i.e. proving this theory)!. Also I try not to let the OH's overlap too much in their pickup area to prevent phase related problems. As I go on I more and more firmly believe that phase is the key to getting even better recordings.

    on a boring sidenote Studiomaster (rip) had a desk that had the LR reversr polarity to the subgroups so if you routed to LR and a group (say when you wanted vocals higher quickly) you'd loos it all-Very clever!

    Sean
     
  9. RecorderMan

    RecorderMan Distinguished Member

    Joined:
    Mar 28, 2001
    ...interesting points Kev.
    1.I have noticed tgrough my travels that the "mains" in some control rooms (I'm speaking of a standard westlake style configuration...where you''ll have two 15" woofers and a horn for each speaker...in the wall) would have the woofers reversed phase. I've asked about this and was informed more tghan once that it related to the tuning of that particular room. It varied from room to room.
    2. If you use an "absolute phase" clicker; a positive waveorm from the clicker will give you a positive polarity (or positive phase) reading when the speaker has a positive excursion (out of the basket).
    3. Speaking for myself, i find that a kick sound that pushes the cone out on the initial attack is punchier.
     
  10. sixpence

    sixpence Guest

    Normally the reason a woofer/tweeter combination is reverse polartiy to each other is to provide a smoother response in the crossover region.

    Sean McC
     
  11. osmuir

    osmuir Guest

    getting phase right on drums confuses the hell out of me [listen listen listen...um eh um]. lot of indecision for me.

    anywhoo: 1. now i'm working with fewer and fewer drum mics [FOK, stereo over kit]. maybe snare.
    is this a good way to cut down on variables?

    also: when editing drums, i'll often try to check phase by not only flipping 180, but looking at the drum wave forms, and trying to slip them back and forth in time so the waves line up...
    is this valid? sometimes it works, sometimes not. sometimes it just drives me crazy.

    some day, i think i'll just move to monoland!

    thanks.
    --owen
     

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