How to record a kick drum
Although bass drum is rarely the defining element of a song, quite a few classic hits just wouldn't be the same if they had a different kick sound. Try to imagine, for instance, Led Zeppelin's “When the Levee Breaks” with a dull, thuddy, disco-type bass drum. Or at the other extreme, how about the Commodores' “Brick House” with a huge, boomy kick? Clearly, such changes would make either song sound and feel very different.
The fact is that the sound of the kick is often critical to the success of a mix, particularly in rock, dance, and other types of music for which the bass drum plays a foundational role.
But what's the best way to record bass drum? One challenge is the big range of bass-drum sizes that today's engineer is likely to encounter, from tiny 16-inch boppers to 26-inch behemoths. Various tunings, head configurations, and types of heads can also affect how the recording engineer approaches capturing this bottom-dwelling instrument.
In this column, I'll offer some tips and techniques for recording kick drums. Of course, my prescriptions are meant only as guidelines; your own results will necessarily vary depending on the recording space, drum, heads, tuning, muffling, mics, preamps, recording medium, and so on.
May I suggest?
For obvious reasons, it can be difficult to suggest changes to setups when working with drummers who bring their own kits into your studio. Still, some scenarios may warrant polite intervention from the recording engineer.
A relatively common problem is worn-out or “dead” drum heads. Note that a head can look okay and still be sonically dead. Worn-out heads will almost always lack a strong fundamental tone — a thin, one-dimensional sound coming from an otherwise decent drum should send up a quick warning flag. Another telltale sign is a head that must be tensioned tightly just to producea tone. That usually means the head has been beaten so long and hard that the material (typically Mylar) has stretched or is pulling loose from the collar.
For engineers who record lots of different bands, it makes sense to have a few new replacement heads on hand. For kick drum, the most common sizes are 20 and 22 inches. One of each size should suffice.
Unwanted noise from kick-drum pedals can also present problems. Though the sound of John Bonham's squeaky pedal may be an endearing feature of some Led Zeppelin songs (at least to Zep heads), the usual goal is a silent pedal. Solo the kick and overhead mics and listen carefully for any squeaks, scrapes, clicks, or other unwanted sounds coming from the pedal. If the pedal is making noise, applying a drop or two of lightweight oil to moving parts — springs, bearings, hinges, or what have you — will usually take care of it.
Finally, a word about attack, the “click” of the beater striking the bass-drum head. For pop-oriented drum tracks, as well as many others, a well-defined attack is an important part of the composite sound of the kick drum. A mushy felt beater is not going to make the job easier. Therefore, you might also consider keeping on hand a hard plastic or wooden beater, which will help emphasize the attack.
The jazz kick — think early Elvin Jones — is traditionally a small drum, typically 18 inches in diameter, fitted with single-ply heads front and back, with little or no damping. The heads are often tensioned fairly tautly, which, combined with the lack of damping, can result in the drum sounding more like a low tom than a standard kick. (The playing style adds to the effect: rather than be relegated to timekeeping and low-end syncopation duties, like a rock bass drum, the jazz kick is more an equal voice in the drum kit, often with as much say in accents, rolls, and phrases as the snare and toms.) Some players tame a bit of the resonance with one or more felt strips stretched across the head or heads and secured beneath the hoops; others prefer to leave the drum “wide open.” Either way, the traditional be-bop kick produces a resonant tone, making it quite a different beast from the usual thumpmeister.
Jazz drummers tend to be particular about tuning and the overall sound of their kits, so accuracy of sound capture is usually key. In multimic setups, I have achieved my best results using a high-quality large-diaphragm condenser mic positioned anywhere from six inches to two feet back from the kick drum, with the capsule (in cardioid mode) parallel to and facing the resonant head (see Fig. 1). One of my favorite mics for this application is the Neumann FET U 47; I have also gotten excellent results using my Microtech Gefell M71KMT.
Up to a point, the farther back you position the mic from the kick, the more natural the drum will sound, because the low-frequency sound waves have more time (space) to develop. Because this approach captures not only the sound of the kick drum but the sound of the rest of the kit as well, mic placement is critical. Most importantly, make sure the signal coming from the kick-drum mic blends in well with the other drum-mic signals.
In the case of a jazz kick that is too resonant for the track, a quick and easy fix is leaning a pillow against the resonant head. The larger the pillow is — and the more contact it makes with the head — the more damping will result.
Hole in the front
The double-headed kick drum with a hole or port in the resonant head is popular among drummers in many styles because of its versatility. Generally preferred for pop, rock, and funk, double-headed-with-port kick drums are usually in the 20- to 24-inch range. Often these drums will have batter heads that are double ply (possibly oil filled) or fitted with a semiperforated edge muffler. Depending upon the application, the drummer may have fitted the drum with some form of extra muffling to further damp the heads. Mufflers come in all shapes and sizes, ranging from felt strips to pillows or blankets to purpose-built contraptions. In general, a muffled double-headed kick with a port provides a nice balance of attack and some resonance.
The port opens up (pun intended) some options when it comes to miking the drum, allowing you to position a microphone fully or partially inside the drum or even to use two mics (more on that in a moment). A single-mic setup that has worked well for me has been to place a large-diaphragm, unidirectional dynamic mic — for example, an AKG d12e or EV RE20 — just inside the port and facing the batter head. That gives you the archetypal “basketball bouncing” kick-drum sound, which is often desirable for pop, rock, and funk tracks. As always, small changes in mic positioning can yield very different results, so make sure to experiment. For more attack, you can aim the mic toward, or move it closer to, the point where the beater strikes the head; for more resonance, pull the mic back or aim it more toward the shell of the drum.
The double-headed-with-port kick drum is a good candidate for using two microphones, one inside the drum and the other outside. The internal mic is used primarily to capture the attack transient while the external mic picks up the overall ambient sound of the drum. If you are adding a second mic, it is customary to use a large-diaphragm condenser; however, good results can also be had with other types of microphones, most notably boundary-layer mics such as pressure-zone microphones (PZMs), which can be placed on the floor directly in front of the drum.
When using two microphones, pay particular attention to ensure that the two mics are not significantly out of phase with each other, which can lead to a deterioration of the sound — thinness or hollowness, typically — when the two channels are combined. To check for phase problems, solo the two channels with one fader up and the other down and then listen carefully as you bring up the second fader. Simply put, the sound should get better — fuller, clearer, better defined — not worse. Another way to test for phase problems is to reverse the polarity on one of the mic channels (whether at the preamp or channel strip) and listen for changes in the quality of the sound. Then, choose the polarity configuration that sounds best.
Even when you use just one microphone, the ratio of initial transient to fundamental tone can be modified significantly with compression. If you want more attack, slow down the attack time; if you need more sustain, set a longer release time. One of my favorite units for altering the ratio of transient to fundamental tone is the SPL Transient Designer 4, a unique dynamics processor that allows you to emphasize or smooth the attack and extend or shorten the sustain without introducing other compression characteristics (see Fig. 2). (SPL also offers the Transient Designer 2, a lower-end version of the same processor.)
If you're after the ultimate in smack and dryness, the single-headed kick is the way to go. Generally, single-headed kick drums are at their best when muffled, typically with a blanket or large pillow resting snugly against the lower portion of the batter head.
On single-headed kicks, a good, if slightly retro, sound can readily be captured with the ubiquitous Sennheiser MD 421 dynamic microphone (see Fig. 3). If you want a sound that's even more bandwidth limited, try deploying a Shure SM57. A condenser microphone can serve up a great kick sound, too, especially if you are looking to emphasize attack. Do some research first, though — not all condensers can handle the high SPLs a kick drum delivers.
Because the drum is open to the studio, you can expect more leakage of the bass drum into the room microphones and other mics used on the kit. There are several ways to get around that. One is to apply a gate to the drum track. However, that is almost always better done during the mixdown stage — after all, you can't “ungate” a sound after the fact.
A good way to treat the problem at the source is by walling off the sound, either with thick blankets draped around the drum and mic (which also attenuates the loudness of the drum somewhat; see Fig. 4) or through some kind of tunnel that fits around the drum and channels the sound to the kick-drum mic. The tunnel approach is especially helpful because it lets you move the mic back from the drum, thus bolstering resonance (by allowing the bass waves to develop) while minimizing leakage from the rest of the kit.
One way to build a tunnel is by bending a fairly stiff rectangular piece of carpet into a semicircle and then fitting it around the drum, using tape, clothespins, or whatever to secure it in place. A quilt or thick blanket draped over the top of the carpet tunnel will provide even more isolation. Because the front of the tunnel remains open, any leakage that does get through to the other mics will sound relatively natural (as opposed to the more muffled sound that results from simply draping the drum and mic with a thick blanket).
My favorite thing to use for a tunnel is a Sonotube — one of those heavy cardboard tubes used as a form to pour cement into. They can be purchased from building-supply stores or lumberyards for $10 to $15 apiece. Diameters vary considerably. I have some 24-inch-diameter tubes in several lengths — 2, 4, and 8 feet. The 2- and 4-feet ones get the most use in my studio (see Fig. 5).
You can also use smaller-diameter tubes — an 8-inch-diameter PVC pipe, for example — to capture more unusual bass-drum sounds. This technique is most effective on double-headed-with-port kick drums. If possible, match the diameter of the tube to the diameter of the port. Position the tube flush with the head at the port and mic the drum at the other end of the port. This typically provides a whoosh sound and resonance from the pipe, which can sound really cool — or really bad, depending.
The late John Bonham had a penchant for oversize drums, but it wasn't the size of his drums alone that resulted in his typically monstrous kick-drum sound. A large component of Bonzo's sound came from the massive rooms the songs were tracked in — something to keep in mind if you're trying to get a similarly huge sound.
Still, a 24- or 26-inch kick with two heads, no port, and little or no muffling is going to make a big sound in almost any room. Like the open-tuned bop bass drum, it is usually better treated as part of the kit rather than as a separate instrument, meaning that you should get some distance between the drum and the microphone. Not only does that allow the low-frequency waveforms to develop, but it also helps avoid picking up any resonant “flub” from the movement of the resonant head. A high-quality large-diaphragm condenser microphone placed a couple of feet away from the kit and aimed toward the kick drum is probably your best bet. This positioning also allows for capture of room resonance — again, a critical part of the sound if you're after a huge Bonzo-type kick. Experiment with positioning to find just the right balance of direct drum sound and reflected room resonance.
Insufficient attack is a shortcoming that is not uncommon with this setup. In that case, try positioning a second mic — a Shure SM57 is a good pick — on the batter-head side of the kick with the capsule aimed at the point where the beater strikes the head. However, because this mic is aimed in the opposite direction of the large-diaphragm condenser out in front of the kick, the signals the two mics pick up will naturally be out of phase — around 180 degrees out, in fact. Conventional wisdom holds that it is therefore necessary to reverse the polarity on one of the mic channels. Though this is often the case, try all the possible permutations of polarity settings between the two channels — sometimes what should sound best in theory doesn't do so in practice. After determining which settings yield the best sound, the two signals can be mixed to one channel during tracking or, better yet, recorded to two separate tracks and blended together during mixdown.
Mixing it up
Unless you are truly blessed, some EQ or other signal processing will often be required to make the kick-drum sound “fit” into the track. Although it is possible to process the sound before it hits your recorder, it's usually best to concentrate on capturing a clean representation of what is coming from the drum. On the other hand, occasionally a bizarre sound can inspire similar madness in all subsequent tracks — if that's where you want to go, by all means, print the processed track as is.
However, try to limit premix processing to minor EQ adjustments — after you've exhausted the possibilities for tonal improvement by way of drum positioning in the room, drum tuning, and mic selection and positioning, of course. Rather than boosting specific frequencies, try cutting. Usually, a cut in the 400 to 600 Hz region will remove tubbiness and make for a tighter, more powerful sound. If you aren't getting enough attack, try boosting somewhere between 2 and 5 kHz.
As for compression, the primary reason I compress a kick drum when tracking is to bring out the low-frequency ring and boom — components of the sound that happen after the initial transient. A good compressor can really bring out the resonance yet maintain or even enhance the desirable click from the beater. Note, however, that I record primarily to 2-inch tape. For those recording to digital media, it may be advisable to use a compressor or limiter also as a means to avert digital clipping.
In addition, noise gates can be effective for removing sounds (snare, hats, or whatever) that occur in the spaces between kick-drum hits. If the decay of the drum starts to sound odd, try using less than the maximum dynamic range the gate offers.
No matter how carefully you record a kick drum, it's always possible to discover (usually after the drummer has packed up and gone home) that the kick is too thin sounding or just isn't working for the track. In the case of it sounding too thin, you can beef up the sound by means of a low-frequency oscillator used in conjunction with a noise gate that features a key input. To do this, first split (mult) the kick-drum signal and insert one signal into the noise gate's key input. Next, insert a low-frequency tone from a synthesizer or another oscillator into the gate's input. Experiment with the length of time that the gate stays open and the frequency of the tone. Long gate times will yield a booming, Roland 808-type kick. (By the way, the sound used by Roland in the 808 is actually a floor tom tuned way down.)
As a last resort, a drum module with trigger inputs can mean the difference between saving a track and rerecording it. Most models will have a gate and sensitivity control that allow the unit to reject unwanted sounds on the kick-drum track. If not, it may be necessary to insert a gate between the tape output and the drum module. Of course, for those working on computers, drum tracks can readily be replaced, either manually (one hit at a time) or with the help of automated software such as Digidesign's SoundReplacer for Pro Tools.
It is all relative
When recording drums, keep in mind that most any drum will sound good if monitored loudly enough. Therefore, monitor at low levels, at least during the initial setup, to limit the “flatter effect” caused by sheer volume.
Another thing to be aware of is that your impression of the drum sound will change once the rest of the instruments are added to the mix. Thus, in addition to soloing the kick and other drum channels, make sure to audition the drums along with the other instruments. That way you can ensure that the sound is working for the song.