Tel: 905–690–4709 dk@tfwm.com - Darryl Kirkland, Publisher

Much to Gain: Striving for the optimal sound in drum kit mic’ing

Live instrument mic’ing is no picnic. Especially when there are multiple elements on a stage that an audio mixer wants to capture and reproduce properly. With acoustic drums, the issue is compounded exponentially given that in order to isolate each drum “voice” correctly, you really need a heck of a lot of mics. Or do you?

There are a thousand ways to mic and mix a drum kit with success. Conversely, there are a million ways to mic and mix a drum kit without success! So, given the potential complexity of this process, what are some ways to stave off a drum mic disaster?

Mic’ing drums should always start with a few questions. What is the musical style and sonic goal you are going for? It tends to break down into two basic approaches: “traditional” and “close mic’ed”. Are you seeking a naturally balanced, traditional drum kit sound or a close-mic’ed drum kit sound? The former employs one or more overhead mics plus a kick drum mic and is a more purist approach, common in styles such as classic jazz. The latter requires a close-up mic on each drum in the kit plus a hi-hat mic and one or more overhead mics and is typical of modern pop and rock styles.

Traditional approach

This approach is aimed at maintaining the acoustic balance of the drum kit as produced by the drummer. The main key is mic placement. When properly executed, it largely avoids audible phasing (destructive comb filtering) problems. Detailed measurements are often used for exact mic placements – seriously, techs sometimes use a tape measure to make certain the snare drum is equidistant from multiple overhead condensers. Comb filtering, here, is a degradation in the sound quality that happens when multiple mics are mixed together with slight timing offsets due to placement.

This drum mic’ing style yields less gain-before-feedback in sound reinforcement situations and is most prone to leakage if there are loud adjacent sound sources. It also requires excellent musical balance by the drummer and offers very little balance control to the audio mixer – whether good or bad. In addition to the overhead mic(s), a kick drum mic may be added for extension. Only two or three audio channels are required.

Closed Mic’ed approach

This approach uses a microphone focused on each drum, plus a hi-hat mic and one or more overhead mics. The style offers increased gain-before-feedback and exceptional balance control to the sound mixer, but largely ignores the natural balance of the drum kit. As the sound mixer has far more control, he/she assumes the responsibility for correct kit balance. Upwards of a dozen or more audio channels are required. Comb filtering is an often present and accepted (or overlooked) compromise in the close mic’ed approach. This sonic degradation can sneak up! When putting several mics in a kit, inter-leakage is also a real concern. So, where we point the nulls of our mics may be as important, or even more important, than where we point the front of them! Nulls are the least sensitive sides of the microphones.

Note that it is common to have some combing between the spot mics and the overhead mic(s). This is because the snare, for example, is picked up almost immediately by its spot mic but is also heard in the overhead(s) with a bit of delay – just several milliseconds. This is a compromise that may be accepted. It is treatable in some digital console applications by using channel delay to “line up” such spot mics with the slightly delayed overhead leakage. Such alignment is audible as a clearer sound. But, often mixers must endure the influences of comb filtering as a trade-off to the close mic’ed technique and just mix around it. There is still no tool as important as the human ear!

Mic’ing Process

Overhead mic’ing
Cardioid condensers are the popular choice for overhead mic’ing. Whether one or two, the question must be asked – are the overhead mic(s) actual full kit mics (as in the traditional approach), or simply cymbal mics? As “kit mics” they should be positioned to hear everything in the drum set in a balanced fashion. As “cymbal mics” they should be hi-passed aggressively to help avoid leakage from various drums, and positioned to focus only on cymbal sounds, rejecting the rest of the kit as much as possible.

But why two mics (in either approach style)? Seriously! If there is a good reason to use two spaced overhead mics, do it (maybe true stereo mixing, for instance). But unless there is, one is probably better, as the common “spaced pair” mics naturally bring along timing problems when combined, and this may result in that comb filtering thing again – those partial sound cancellations that we don’t want to deal with! Or, use a coincident pair of mics (a “together” pair) over the kit to eliminate the timing issues in the overheads. See figure 1 for the difference.

Kick drum
What’s the point? Everyone has an opinion on the best kick microphone and the best placement. It is never fully predictable, and always requires listening. A good dynamic on the front side, often in or near a cut hole, may bring all the “thud” you want. A good condenser can specialize in that “snap” attack sound, either inside or on the beater head. Both are valid sounds, but deciding which is appropriate is the challenge. Maybe some of both – this is why some techs choose to double-mic the kick/bass drum and blend to taste.

But this double mic’ing of the bass drum should only be done if the mixer understands and accepts the phasing issues that come with it. Similar to spaced overhead mics, there will be some time offset that partially cancels the sound. Again, digital console delay may be used for alignment here.

Snare drum

A rugged dynamic on the top head of a snare drum can be all that is needed to get the crack and tone you want. If not, try another mic & placement, or fix the drum itself. Again, remember that the snare may cut through in the overhead mic(s) enough already. There is a lot of room for personal mic taste here. Listen and play with mic position for the desired sound.

Consider adding a condenser underneath, facing up into the snares for specific control of that unique high frequency sound. This mic position by itself can sound quite bad, but makes a nice overall contribution when blended with the top mic. Reversing polarity (not phase!) of the bottom snare mic is a common choice. Sometimes it sounds better, sometimes not (too many variables here to predict). It is necessary to listen with and without polarity reversal and choose which sounds better. The mixing console may include a polarity switch on each channel – if not, flipping pins 2 and 3 in the mic cable will get it done. And EQ is just a matter of taste.

Hi-hats

Easy. Get a good cardioid condenser and hi-pass the snot out of it. Right? Well, that probably sounds great for the hi-hat alone. But any time we place a condenser in or near a drum kit, the real trick is to hear the target source while also not catching extreme leakage from the snare and other sources. Experiment with placement.

Rack Toms

Whether selecting a dynamic or a condenser, a stand-mounted or a miniature clip-on mic, the usual plan here is to provide one mic for each rack tom, giving great isolation and ability to process individually. As the rack toms are not often played every measure until there is a drum fill, it is common to gate them aggressively until they are actually played. Otherwise, they idly contribute lots of useless leakage which deteriorates the overall kit sound. EQ these if desired. It is not uncommon to see sound techs aggressively scoop out the low mid or mid range section of rack toms to suck out the “boxiness” or even boost the high mids for extra snap, or boost the bass for more thud. EQ should be used only after mic selection and position are optimized. Listen!

Floor Tom

Very much like rack toms. We might make a different mic choice to accentuate low end if it is a large drum, or high frequency attack, if desired.

Mixing Process

Natural Kit Mixing
The drummer’s balance is the key. Pan overheads appropriately, if more than one and if intentionally building a stereo mix. Blend in a bass drum mic if needed.

Close mic’ed mixing
First, decide if the overhead(s) should be kit mics or cymbal mics. In this style, they are usually only cymbal mics, so they should be hi-passed as much as possible (at least 400Hz) to reduce leakage. Listen to what items remain audible and balanced in the overhead mic(s). It may be that the hi-hat or the snare (or something else entirely) have enough “lift” already. If so, consider not using those associated spot mics. In cases like these, less might just be more.

Panning multiple overhead mics for stereo
If using more than one overhead and doing so in an appropriate stereo environment, pan the mics accordingly. But remember that mono does not mean lo-fi, and can actually sound great in PA work. It is actually the best choice in a number of worship sound reinforcement venues. Regardless, “mono checking” a stereo and/or multimic’ed drum mix is a smart move to be warned of phase cancelled sound. Broadcasters and recordists typically have such a mono-check button in their control rooms, but live sound operators may have to figure out how to mono-sum-monitor. Again, using a single overhead or a “coincident pair” (revisit figure 1) minimizes problems when the mics will be combined (mixed) to mono.

Blend

Once all kit elements are checked individually, it’s time to blend. Here are two mixing approaches, but there are many:

Use only the overheads first and then add kick, snare, hi-hat, racks, etc. as needed.
Start with kick and build up from bottom through snare, hats, rack, floor and overheads.

It may sound nuts, and it will annoy a sound check bystander or two, but attempting both approaches back-to-back quickly leads to the correct final balance. Then, final EQ and pan adjustments can be tweaked. Dynamics processing (compression, limiting, and gating) is largely a matter of taste, with the exception of gating rack and floor toms and maybe kick, which is just generally good practice for this drum mixing style. Advanced dynamics processing for drum mixing, such as parallel compression, is a complete topic in itself.

In regards to panning- if you’re going mono, don’t do it. If you’re going stereo, get the overheads right first! These will set the initial spatial image (“width”) of the kit. Then, listening carefully, use the pans to closely match the position of each individual mic to the image already created in the overheads.

Final Thoughts

Great drums mixes start with great sounding drum kits. Before mic’ing up a live drum kit, make certain that it is a good sounding kit in the first place. Begin by listening to the set without the mics.
Drums can get loud – use mics with high SPL capability!
You can get amazing drum mixes with both mic’ing techniques described. The purist technique is hardest to mic really well. The close-mic’ed approach is hardest to mix really well.
Successful multi-mic’ing of a drum kit demands a solid understanding of microphone polars, or directional behavior. Inter-leakage WILL occur.
Electronic drums eliminate the common loudness and leakage issues associated with acoustic drums. Sometimes they may the best overall choice for a live worship environment. But, sonically and musically, acoustic drums are very hard to beat, especially with a seasoned drummer that can play with appropriate dynamics for the environment.
Never underestimate the value of an accomplished drummer!

SIDEBAR:

Drum Shields

Acoustic drums are usually loud. Sometimes that’s ok. However it can be a problem on a stage with many open mics and such. The ideal situation involves a drummer with excellent playing dynamics, and an acoustic environment that supports great “ensemble” work. But sometimes stage volume and leakage gets out of control regardless of your best laid plans.

Drum shielding, in this author’s opinion and experience, is not the end-all solution that some may believe it to be for the live worship stage. It can certainly work, and work well, but it can also create new problems. As one industry peer recently noted, “The best benefit from shielding acoustic drums on the live stage is the minimization of cymbals/high frequency bleed into the vocal mics”. The idea with drum shielding is to use an acoustic barrier minimize the leakage into the other stage sources and even into the house seats.

There are three basic kinds of acoustic devices: absorbers, diffusers, and reflectors. Absorption would make sense here, but since we need our drum shields to be visually transparent, they can’t be covered in fuzzy stuff. They must be thin, rigid, and clear. This means that they are either mostly reflective or possibly diffuse, or a combination thereof. Note: Some designs do have absorptive material along the bottom regions, below where sight lines would be impacted.

Also, the ultimate isolation of a live drum kit is achieved when a lid is added to the shield enclosure. At this point, we’ve effectively put the drummer in a “box” for the ultimate in isolation. This has its control advantages, but can be a problem for keeping him/her feeling “connected” to the live worship event.

Amazingly, some drummers can overcome such isolation. In this case, it is absolutely critical that a good monitor mix is provided (whether wedge or in-ears) for the drummer, as they are now acoustically disconnected from their bandmates. If that monitor signal fails or is incorrect, the drummer is baked.

While drum shields are an appropriate compromise on a number of modern worship stages, it is possible and not uncommon for hard, clear drum kit shields to work against the sound quality rather than for it. They can induce audible, nasty comb filtering into the drum overhead mic(s). The reflections from the drums hitting the reflective shield get back into the overhead mics with some delay. The sound quality is impacted.

So, shields can work! They can also cause degradation of the drum sound. It becomes a choice of compromise, need, and optimization. Understand the details, and experiment accordingly.