A fresh look at drum kit microphone techniques; taking a less conventional approach...
January 10, 2017, by Jonah Altrove
My father used to say, “Son, opinions are like drum miking techniques. Everyone has one.” Or something like that…
Truthfully, there’s an overwhelming amount of information already out there on this topic, so rather than rehash it here, let’s explore a less conventional approach. I’ll admit that it’s a unique method, as it’s a hybrid of studio techniques and some ideas “begged, borrowed and stolen” from engineers I admire.
Picture a snare drum. Let’s mike the top and bottom heads. Remember that in a properly wired system, a positive pressure on the mic’s diaphragm creates a positive voltage on XLR pin 2, which pushes the loudspeaker cone forward.
OK, now hit the drum. Bang. The stick pushes down on the drum head, which moves away from the top mic (negative pressure) and towards the bottom mic (positive pressure). This means our bottom mic’s initial transient is a positive voltage, while the top mic’s is negative. (If you doubt this, make a recording and use DAW software to zoom way in on the waveform.)
We send both signals to the PA and create a tug of war at the loudspeaker cone, which is being told to move in and out at the same time. This creates a partial cancellation that’s very audible, typically as a loss of low-end “body” in the snare sound. Luckily we have a polarity inversion switch on the input channel, which “flips over” the waveform (by swapping XLR pins 2 and 3 at the preamp), so both transients are headed the same direction.
I don’t intend to enter the fray regarding whether absolute polarity is audible (most research suggests that it is not). Rather, let’s focus on keeping as many of our drum inputs as possible in polarity with each other. Convention and AES Standard both say positive pressure = positive voltage = outward (toward the audience) loudspeaker movement, so let’s go with that.
Start with Input 1, the kick drum mic. The beater (the part of the pedal that strikes the drum) will push the drum head forward (away from the drummer), which is toward the kick mic. It’s pretty common to mike both inside and outside kick, but they’ll both generate a positive transient.
It’s conceivable that the kick and snare would be played at the same time, so shouldn’t they be in polarity with each other. If we follow standard practice of inverting polarity on the snare bottom, our kick transient is positive-going, while both snare channels are negative-going. For this reason, I advocate flipping polarity on snare top instead – now kick and snare are all positive transients coming through the PA.
Basically, any part of the kit miked on the same side it’s hit is going to generate a negative initial transient, so let’s flip the polarity on all of the tom mics. I occasionally use a bottom mic on floor tom, so that can stay positive.
And now we come to the cymbals. I have a confession to make: I have overhead drum mics. In the studio, they’re great – studios spend a lot of money creating a pleasing acoustic environment, so overheads, room mics, and ambient mics can yield good results.
However, there isn’t a huge sound system blasting that room sound back into the room. I’ve always thought it a bit odd that we strive for maximum isolation on every other input, then hang super-sensitive condenser mics several feet above the stage. Solo overheads in your headphones some time and listen to how much “room sound” they’re leaking into your mix.
So instead, I utilize underheads. There are a variety of “clips and claws” that can be used to mount mics straight to the stands underneath the cymbals. This does a number of good things:
—No additional mic stands needed
—It’s low-profile, in nobody’s way, and there aren’t mics bouncing around above the drummer’s head, which I always find distracting
—Isolation is much improved; there’s less bleed from the other parts of the kit (hold that thought) because the mics are pointed away from the drums. Further, this rejection can be fine-tuned with hyper or supercardioid mics to reject the snare, which is the worst offender
—Set up is really fast
—To me, it sounds better – tighter and cleaner, which to my ears has much more clarity
—It preserves the polarity of the drum kit
Pros & Cons
Like anything in audio, using underhead cymbal mics has its downsides (zing!). For starters, there’s likely the need for more inputs, as close-miking necessitates a mic for each cymbal or small group of cymbals. If the drummer has a gargantuan kit, this might be a concern. There will also be more open mics, but gain before feedback actually seems to improve with this approach. Here’s why.
Let’s say a standard overhead mic is 3 feet from the cymbal, and our underhead mic is 1 foot away. That 3:1 advantage in SPL translates to 10 dB less gain needed at the preamp to get the same level in the mix. We’ve effectively attenuated room noise by 10 dB, increasing the signal-to-noise ratio (SNR). This is the mechanism that drives the close-mike approach to isolation, which dominates our live sound strategy.
Also be aware that under-miked kits can be harder to mix. Since an overhead picks up everything, it naturally preserves the balance of the drummer’s performance. With close mics, a lot more attention needs to be paid to making sure the elements of the kit are balanced in the mix. This can be a lot to juggle.
Finally, be aware that the “close-miked sound” is not appropriate for all styles of music. For example, often with jazz a single overhead is the only drum mic, relying on the player to balance the sound.
TNT, I’m Dynamite
Speaking of which, let’s talk about kick drum EQ for a minute. Imagine you’re at a rock concert. What does the kick drum sound like? OK, now imagine how the kick drum might sound at a hip-hop show. Then picture a jazz band. You can see that any across-the-board advice on how to EQ a kick drum should be looked upon with suspicion.
There must be a consideration of the genre of music, as well as the expectations of the audience. Fans at a Chick Corea concert would be extremely upset if the kick drum sounded like some sort of explosive device detonating. Fans at a Five Finger Death Punch show would be extremely upset if it didn’t.
Having just advised against any blanket statements regarding kick drum EQ, I’m now going to make a blanket statement regarding kick drum EQ. Here’s a little trick that I have been using for yours before I discovered why it worked. So let’s start there.
A Pultec EQP-1A with pots for both boost and cut.
Although you’d be excused for not having seen it in a live setting, the Pultec EQP-1A is a mainstay in recording studios across the globe. Examining the front panel reveals a curiosity: each EQ band has two gain pots: one for boost and one for cut, a head-scratcher for sure.
What’s really going on is that the attenuation frequency is intentionally offset from the boost frequency by about 100 Hz. If you set the EQ to boost kick drum resonance at 60 Hz, the attenuator pot would add a cut around 160 Hz. This creates a gentle yin-yang shaped curve that makes the boost sound bigger that it actually is, which really “tightens up” the sound and makes some room for the bass guitar. So if you like to use LF boost at the kick’s fundamental frequency (usually 50 to 60 Hz), you can emulate the Pultec curve by adding a gentle cut a little further up.
By the way, that 18-inch sub behind the drummer? Yeah, the one that he keeps asking you to turn up? Kick drum transients push the drum sub loudspeaker cone outward – towards the kick drum head – which can sympathetically resonate the drum head, like pushing a kid on a swing. Flip the polarity on the drum sub and its excursions are now opposite those of the drum head, which can actually damp the head a bit and buy you a few extra dB of gain before feedback. You know, so you can turn it up more.
Finally, it may be worth having a conversation with the drummer about his mic preferences. I asked a drummer buddy about this, and he said, “I don’t care as long as nothing’s in my way.” He also told me that he’s particularly sensitive to “too much going on” in the space between the hi-hat and snare drum. Good things to know when I go to mike up his kit! A quick chat with the drummer can streamline the process and prevent having to make changes later.
Ask 10 drummers – or 10 sound engineers – and you’ll get 10 different suggestions for how to mike a kit. And that’s fine. Ultimately, let you ears be the judge. If it sounds good, go with it!
Jonah Altrove is a veteran live audio professional on a constant quest to discover more about the craft.