This morning I sat in church listening to a wonderful 150-voice choir, an 8-person front-line vocal team, a 40-piece orchestra, and a tight rhythm section that included a grand piano, Hammond B3, electric and acoustic guitars, electric bass, and a full acoustic drum kit.
Because there were so many acoustic instruments and voices being miked, the drums were in a fully enclosed plexiglass booth. The sanctuary stage is not an ideal acoustic environment for all this sound in close proximity, but it’s workable for most arrangements.
However… Today, for some reason, the house engineer was running the overhead drum mics way too hot in the mix. What a waste of amazing talent. So, what’s my problem?
The problem was the constant drone of metallic hash noise coming from the ride, splash and crash cymbals. Why are you (you know who you are) miking and routing those cymbals to the main mix bus? Well, maybe death metal engineers can get away with it, but for everyone else, please continue to read on.
More Harm Than Good?
Having spent a good deal of my pro audio career in the studio or behind a front of house console, I’ve never understood the fascination with overhead drum mics. In the studio, sure, I get laying down discrete overhead tracks that can be carefully used in the final mix. But for a live mix, not so much.
I love a good sounding drum kit and have long felt that when properly tuned and mixed, a great-sounding kit can make any combination of other instruments and voices sound better than the sum of the parts. But I think the ride, splash and crash cymbals do more to ruin an otherwise good mix than any other class of instrument.
In my humble opinion, allowing overhead mics to pick up and amplify these cymbals ruins the mix, and here’s why: the upper mid-range tonal spectrum gets too crowded. Cymbals occupy a wide swath of the audible frequency spectrum (Figure 1). And when hit hard, they contain a significant amount of transient energy (Figure 2), and decay much more slowly (Figure 3) than all drum heads.
Amplifying cymbals is particularly bad because of how the tonal spectrum masks other, more deserving sonic content, specifically vocals. Cymbals just raise the noise floor of the overall mix for no good reason. You might as well just feed pink noise into the output bus and raise the level until it’s obviously annoying.
Even without amplification, cymbals can easily overwhelm solo and background vocals, strings, acoustic guitars, woodwinds, keyboards, and a whole host of other instruments that have fundamental, and second and third harmonic tonalities between 400 Hz and 10 kHz. 
The only cymbals I consider worthy of miking for live reinforcement are the high-hat pair, presuming the drummer isn’t too heavy handed when the pair are open. There are many effective ways to mic the hat, so I won’t go further into that topic.
If you absolutely have to deploy a couple of overhead mics (e.g., because the drummer insists they’re needed for his in-ear monitor mix) pull them out of the house mix and only consider bringing up those faders during a soft ballad, when the drummer is most likely playing as light as he ever does.
Or, perhaps consider putting up under-hung mics on each cymbal. The closer placement, and upward facing positions, will reduce much of the drum and room bleed (based on the polar cancellation properties of each mic), giving more control over individual cymbal sounds. But even with this technique, be very careful with the levels.
There’s enough energy coming off most cymbals to easily carry into the drum mics, and likely, every other open mic on stage. Obvious examples are vocal, choir, acoustic piano, string and acoustic guitar mics. I’m sure you can fill in other examples.