| Attack Time In Drums & Multiple Microphone Blurring |
| The attack of a drum hit is established in the first 2-3 milliseconds of
the generated sound wave. This means that when a drum is picked up by multiple
microphones that are spaced apart by more than 2 milliseconds, the attack becomes
"blurred" (less definite). Thus leakage of the snare into cymbal and tom
microphones more than 2 feet away will lessen the snare attack. This same problem
would occur for all of the drum kit instruments. |
| Putting The Drums In Time |
Sound travels at 1130 feet per second. Thus it
takes about 9/10 of a millisecond for sound to travel a one foot distance. Recording
engineers conveniently round this off to the timing formula of 1 ms = 1 foot. |
When you put all of the microphones in time with each other, the attack
of the drums is astoundingly better. Ben Blau, an RID instructor, first introduced
this idea some 8 years ago when he was managing one of our recording studios. I had
been using delay to compensate for spaced microphones on guitars but had never tried it on
the relatively small time differences of the microphones on a drum kit. I expected
somewhat of a difference when Ben explained his idea to me but I was unprepared for how
much of a difference it made.
| To put all of the microphones in time with each other you select a
"focal point" say 6 feet from the floor over the drums. This could be a
place that you used X-Y microphones as overheads, but you use this focal point even if you
don't have overhead microphones there. You measure (or estimate) the distance of
each microphone to the focal point and then delay each microphone by that amount using the
formula of 1 ms = 1 foot. |
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APPROXIMATE
DELAY TIMES TO FOCAL POINT |
FOOT DRUM |
5.0 milliseconds |
SNARE DRUM |
4.0 Milliseconds |
LOWER TOMS |
4.0 Milliseconds |
UPPER TOMS |
3.5 Milliseconds |
HIGH HAT |
3.5 Milliseconds |
| OH CYMBALS |
2.0 Milliseconds |
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| In Practice |
| Delaying all those microphones by the indicated amount will take 8
channels of delay. If you are using a digital console, there is a delay function on
each channel of the console that can be used. If you have an analog console it is
harder because you need individual delay lines. If you are using an analog console
but recording onto an MDM (ADAT or DA-88), you can use the "track delay"
function of the tape machine during mixdown. If you are recording onto analog tape,
you can get partial attack improvement (with less delay lines) by delaying the foot and
the snare track by the time difference between that instrument's mic and the cymbal mics.
In the above example, this would be foot delayed 3 ms and the snare delayed 2 ms.
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