Speed of Sound and Phase

Discussion in 'Microphones (live or studio)' started by Todzilla, Feb 17, 2005.

  1. Todzilla

    Todzilla Active Member

    May 12, 2003
    Neuse River Watershed
    Home Page:
    Can we apply a little math to the problem of phase alignment?

    For example, if I have overhead mics that are, say a half a meter above the snare drum and an undersnare mic that's 4 centimeters below the snare, could I simply apply this formula:

    1) flip phase on bottom snare since bottom skin is outting when top skin is inning...
    2) Delay the undersnare track time by .88160100 miliseconds?

    math: Speed of sound is 340.29 m/s, or .00293867 seconds for sound to travel one meter. Therefore, the distance difference in the mics from the sound origination would be 30 centimeters (assuming a snare depth of 16 centimeters, + 4 centimeters for the mic distance). So the formula would be:

    time for sound to travel 1 meter X distance difference = offset
    .00293867 seconds/meter X .3 meters = .00088160100 seconds

    Is this right? I am slightly more than 350 feet above sea level, so that might be trivial, eh?

    Your thoughts, oh mighty physics nerds....
  2. Massive Mastering

    Massive Mastering Well-Known Member

    Jul 18, 2004
    Chicago area, IL, USA
    Home Page:
    Flipping the polarity on the bottom head is the common technique.
  3. Kurt Foster

    Kurt Foster Distinguished Member

    Jul 2, 2002
    77 Sunset Lane.
    That makes my head hurt.
    What ever happened to just doing what sounds good? Use your ears ....

    My opinion ... less is more ... the fewer mics the better the sound ...

    If the snare needs a mic on the bottom, either the snare sucks or is tuned poorly or you're micing it incorrectly at the top.
  4. zemlin

    zemlin Well-Known Member

    Sep 4, 2004
    Indianapolis, IN
    Home Page:
    If I want to time align, I usually do it visually, confirm with math to be sure the times make sense and use my ears. Perfect alignment isn't necessarily the best sound.

    [edit] Thanks, kev - fixed it [/edit]
  5. Kev

    Kev Well-Known Member

    Nov 13, 2001
    " Perfect alignment is necessarily the best sound. "

    should that have been .... isn't

    I think I can argue the maths here.
    It is all about perspective and as far as a real drum kit is concerned, there is no place near the kit where ALL sounds will arrive at the same time.
    I think you would need to head out to distance and then the signals would be very delayed. ... infinity

    Time aligning all signals will in fact be an UN-natural drum kit.

    might sound cool BUT not technically real

    does that make sense ?
  6. rudedogg

    rudedogg Guest

    i totally agree here. your making music, not computer programs. some delay is what gives it the sound and makes it sound like it was recorded in a ROOM not on mars in a lab.

    I don't necessarily agree with this. less CAN BE more, or it can be just less. in some cases and styles of music, less mikes gives it the correct sound for music, but for every musical style, even for every song, each song will dictate what way you record drums.

    however when tracking drums, more is more, you cannot have enough drum mics. use every mic you have and try different things, don't just stick to the standards that you know sounds a certain way. if it doesn't sound good, throw it away, and don't use the track, but if you don't close mic stuff, you may not be able to get that sound your looking for when you go to mix. if the client says, "yeah, i want more snare sound, i want a crazy tshhhhh" then you better have miked it in a way to capture that sound without saying umm, sorry, this is as good as you get.

  7. Randyman...

    Randyman... Well-Known Member

    Jun 1, 2003
    Houston, TX
    I have tried experimenting with time-aligning my drum tracks. It DOES seem to add focus and power to the part of the kit you used as a reference (I used the Snare), but you also loose a lot of the "realness" of the room. Also, like mentioned, by time-aligning to ONE drum, you still have time issues with the other 8 peices of the kit ;) .

    I also agree that more mics on drums are a better option. I blew off dual micing the snare and kick, and I even blew off Hi-Hat mics for years! That is - Until I saw a studio setup all of these mics on my kit (like $6000-$8000 of mics), and I heard the result! The very next session I did had 2 Kick Mics, 2 Snare Mics, a Hat Mic, usual Overheads and Tom mics, and a room mic. All I can say is the bottom snare mic gave me what I was missing from my recordings previously (My room sucks BTW). You CAN'T rely on overheads for a good snare sound in a shitty room IMO. Practically ALL of your "snare strand" sound will come from the overheads unless you bottom mic the snare. If I had a HUGE drum-room - things mat be different (Sugar Hill had a FANTASTIC drum room, and still used tons of mics on my kit).

    Some say KISS - but I say the more options, the better (ESPECIALLY in a crappy room w/o a control room to accuratelty hear what the mics are doing - I know I am working in "Sweat Shop" conditions here folks ;) ).

  8. Kurt Foster

    Kurt Foster Distinguished Member

    Jul 2, 2002
    77 Sunset Lane.
    As with all things recording, rules are made to be broken and what works for one situation, may not in others.

    I normally use a lot of mics when I do drums. All drums, hat and OHs, sometimes even a ride cymbal... and a bottom snare mic at times when the snare tone really sucks and there's nothing else to do. Still the best drum sounds I have ever recorded were with a C24 on overheads, a C12a on the snare / hat and a D112 on the kick ...

    I have not been using the bottom snare approach since I figured out that by pulling the top sanre mic back a little, the bottom mic becomes unnecessary in most situations. All the bottom mic does is create pahse anomallies that are not always 180 out so no matter what you do its still out of phase and introduce unwanted spill from the kick, again usually out of phase.

    IMO phase relationships are almost the most improtant problem to watch for when recording. Using fewer mics, just creates fewer problems.
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