Mixing Drums for Modern Rock Music

Posted: 16th May 2011 by Mezzanine Floor Studios in Uncategorized

Often the biggest casualty when recording a rock record on your own is the sound of the drums. A lot of attention is paid to the vocals and guitars to make sure they’re just right, and the bass is usually tweaked until it sounds “good enough”, but the drums are often done on a “do what you can with what you’ve got” basis. The result is often drums that lack “punch”, “boom”, “clarity”, “tone”, “snap”, or “warmth”, but instead can be described with words like “flat”, “boxy”, “papery”, even “boring.”

One of the things I’ve found in producing drums is that a lack of punch or clarity or boom often has much more to do with the way all the drums sound together, and much less about the way each drum mic sounds when listened to by itself. Sometimes the sound of everything together is weak because of poor mic choice or placement, poor drum tone to begin with, poor drummer technique, or even recording in a room that is totally inappropriate to the style. All of these things can be hallmarks of Do-It-Yourself drum production.

Sometimes, however, the sound of all the drum micsĀ  sounds bad because of a few simple things that can easily be fixed in the editing or mixing phase.

1. Drum mics often pick up sounds you don’t want them to “hear.” Tom mics are notorious for this- they pick up almost as much snare and cymbals (or kick for a floor tom bottom mic) as they do the intended tom. The solution: At the least, manually go through the song and cut out any material in the tom tracks where the toms aren’t playing. This will instantly tighten up the sound of the snare and cymbals. Sometimes this results in a problem where the tom hits coming in change the tone and clarity of the snare and cymbals because the sound recorded when the tom was hit includes these sounds, too. If this effect is too noticeable, replace the actual recorded tom hits with tom hit samples. Drumagog and Sample Replacer are among the many tools that enable one to do this with ease, or you can do it manually if needed. It’s best if you can get the drummer to record standalone tom hits when in the tracking session- this enables you to replace the tom sounds with ones that sound the same, making your close mic replacements and the tom sounds in the overheads match more than conflict. If this isn’t possible there are a number of good sample libraries out there.

2. Close mics are minutely out of time with the overhead mics. For many styles of music this is not a big deal. Classic rock is notorious for having room mics on the other side of a big room, giving the listener a BIG sounding drum kit that can lack in clarity. In modern rock, however, a tighter, punchier sound is often desired. The Solution: It can often be helpful to remove this effect by nudging the close mics so they are in time with the overheads (See Figures 1a and 1b below for original and nudged sound.) Find a loud hit in the kick and zoom in on the kick and overhead tracks, then move the kick track(s) so the start of the kick in the kick track(s) matches the start of the kick in the overhead tracks. Do the same with the snare and toms (if using samples render them to a clip, then nudge the sample hits to match up, too.)

NOTE: be sure to check the polarity of your drum tracks after doing this. Sometimes it becomes necessary to flip polarity after doing this. The dead giveaway is that you’ll find the waveforms line up perfectly at a zero-crossing and then start the intense transient of the drum hit, but the waveform goes up in one track and down in the other. This gives a clue about which tracks to flip polarity* on.

Figure 1 (original):

 

Figure 1b (nudged):

 

 

* A few notes on polarity and phase:

“Flipping polarity” and “flipping phase” are often used interchangeably by engineers. Flipping polarity is the more correct term, since it means exactly what it says. The part of the sound above the middle (zero) of a waveform in software gets converted into electric current that is positive, which results in a speaker cone “pushing” outward. The part of the sound below the middle (zero) of a waveform in software gets converted into electrical current that is negative, which results in a speaker cone “sucking” inward. Flipping polarity in software takes the recorded upward part of the waveform and processes it so it creates negative voltage that sucks the speaker cone inwards and vice versa.

Flipping polarity is generally done to correct one of two issues:

1) When two mics are placed on opposite sides of a drum, like a top snare mic and bottom snare mic, one mic hears a “push” when the snare is it and the drum head moves toward it, while the other mic hears a “pull” or “suck” as the snare is hit and the head moves away from it. This results in an unnatural sound when the two mics are mixed together, since one mic’s sound essentially subtracts from the other’s sound, leaving you with a “weak”, “powerless”, “hollow” sound in the mid range, lack of “clarity” in the high end, and a significant decrease in the volume in the low end [in this case a bad thing.] By flipping polarity the engineer tells both mics to hear a “push” when the drum is hit.

2) When multiple mics are used to record something there is a time relationship between them, and adding the two recorded sounds together yields strange results. The timing relationships in tracks are related directly to difference of the distance of each mic from the source of a sound. When the drummer hits the kick, the kick mic is the first to “hear” the sound, followed by any bottom snare or bottom floor tom mics, then by the top snare and tom mics, then by the high hit mic, then by the overheads, then by the room mics, etc. When you look at the waveforms in software, it can be seen clearly that the upward movements in the snare mic correspond more closely with either upward or downward movements in the overhead mics at the same time, all of which started when the drummer hit the snare. When the snare and overheads move roughly in sync up and down the snare will sound punchier than when the share and overhead mics move up and down opposite of eachother. Traditionally the method of fixing this problematic phase (time) relationship was to flip polarity on the overhead tracks so the ups and downs in each waveform moved together, resulting in a tighter, fuller sound. The problem with this technique is that the timing relationships vary according to the frequency makeup of the sound, and depending on the distance, the waveforms may not really move together at all. By nudging tracks so they line up exactly, the movements are brought more in line with each other. It is then easy to see when the snare sound moves up in the snare mic and down in the overheads at the same time, making the decision to flip polarity in the overheads an educated, more accurate, and correct choice, rather than an approximation.

A few oversimplified** examples if you can forgive some poor drawings…

In figure 2 the blue sound would largely but imperfectly subtract from the green sound, resulting in a weak and hollow tone.

Figure 2.

By moving the blue sound to line up with the green sound (like the nudging example below, which is a true phase or timing adjustment) we would get Figure 3, where the blue sound is exactly opposite the green in timing, intensity, shape, etc. If played together these two sounds would cancel each other out and nothing would be heard.

Figure 3.

 

By “flipping polarity” on the blue sound we would get figure 4, where the blue sound would add to the power of the green sound more than it subtracts from it. This would result in better tone and greater low end power than the original sound combination in Figure 2, but would still lack clarity since the blue sound lags behind the green sound.

Figure 4.

By moving the blue sound to line up with the green in timing or phase, then flipping polarity if they don’t already match, we would get the best results in both tone and clarity, since the timing (phase) and polarity of the sound match most closely and blue sound would add to the green almost completely (Figure 5.)

Figure 5.

 

** The reason I say these are oversimplified is that real sound isn’t periodic or uniform like this. Even if hitting the snare alone there would be differences in the intensity/volume of the snare sound in the snare mic and overhead mics, as well as differences in frequency content due to the microphone design, the nature of sound in air, room acoustics, etc. When adding in the sound of cymbals, kick drum, toms, high hat, ride, etc. the combined content that reaches each mic will have a unique makeup of frequency, intensity, etc. The point of this article is that it is possible to get closer to ideal results using a hybrid nudging/polarity flipping technique than one can by simply flipping polarity.

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