Drums In the House

Using Ambience To Enhance Your Recorded Sound

One of the most recognizable sonic signatures in the history of rock drumming is John Bonham’s aggressive and roomy sound on “When The Levee Breaks” from Led Zeppelin IV. While Bonham was a monster hitter with a fat drum kit, his sound was made bigger than life on the recording by the employment of a simple miking approach that successfully captured both the kit and the amazing ambience of the space in which the drums were recorded.

This huge sound was the result of just two microphones strategically positioned on the second landing of a three-story staircase above a hallway in which Bonham was playing. The two recorded tracks were then prodigiously squished through 1,176 compressors and run through a Binson EchoRec to imbue the drums with that over-the-top character. That’s extreme room sound at its best. It was a pivotal point in drum recording history that put a new spin on the way people thought about using drum ambience to enhance a composition.

You’ve no doubt noticed sonic changes when you play your kit in different rooms … Sometimes it’s good and, well, sometimes it’s not. But capturing the acoustic reflections of drums being played in a sweet space does most-excellent things for the recording. Room ambience plays one of the biggest roles in how natural, dry, or huge the recorded drums will sound. Since there are different situations and not all are ideal, you’ll need to be armed with a variety of approaches for getting and using room response to maximize your drum recording.

To get a broad spectrum of experience on the topic of recording drums and utilizing room ambience, I conferred with George Borden, the Advanced Recording instructor at Ex'pression College For Digital Arts, solicited input from the History Of Music Production instructor Scott Theakston, and obtained commentaries from world-class engineers Joe Chiccarelli and Eddie Kramer. Here’s the scoop.

Laying The Foundation

Borden is effusive about miking strategies and comments that while it’s standard to close-mike the individual drums when multitracking a kit, it’s not common for a person to listen to drums in such a manner from only a couple of inches away. “Drums that sound most natural include distance,” maintains Borden. “That’s why it’s important to adopt a good miking technique to capture ambience.”

In order to get a good recording, however, the fundamental elements need to be in order. “The drummer, the tuning of the kit, and the sound of the room must all be top drawer,” states Eddie Kramer, who had the pleasure of capturing Bonham’s “ridiculously aggressive” sound on a number of Zeppelin recordings. That said, make sure the kit is tuned well and hit those skins with conviction. As for the room, both Borden and Kramer favor the warm resonance of wood and the expansiveness of 12-foot to 14-foot high ceilings.

But not everyone has access to a castle with vast stairwells in which to hold a recording session. Oftentimes, getting an awesome drum sound enhanced by good ambience can be a challenge to achieve with the various limitations faced by the small project studio or low-budget recording endeavor. If you have a great-sounding space to begin with, then the world is your oyster. If you have a space that's not quite up to snuff, you'll have to pull a few tricks out of your sleeve. Here are some approaches to handle a gamut of situations.

The Room In Real Time

It's hard to beat (depending on how you look at it!) well-tuned drums in a good space. If you're lucky enough to have access to a great-sounding space, some well-placed distant mikes should do the trick. Borden shared several straightforward miking techniques for capturing drum ambience when recording in an acoustically pleasing room.

Place any large-diaphragm condenser - one with an omni-directional pickup pattern is best to pick up more of the room - between six to eight feet out in front of the kit. The room mike(s) must be at least six feet or farther from the close-miked kit in order to prevent problems associated with comb filtering, a phase cancellation phenomenon that happens when mixing together signals from mikes receiving the same sound at slightly different times. If the ambience mikes are at least six feet from the close-mikes on the kit, the amplitude and frequency content should be different enough to minimize phase issues.

The height at which you position the mike will affect the overall sound. Usually the higher you place the mike, the higher the frequency content you’ll be capturing; and the closer to the floor, the more lows you’ll be getting. Placing the mikes higher could serve to brighten up a dark-sounding room, and placing the mikes lower, even as low as one to two feet off the ground, could result in more kick drum and a darker sound (FIG 1).

Fig. 1: Microphone Placement Tips For Capturing Ambience

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Still observing the same minimum six-foot distance rule, another approach entails using a stereo pair of matched cardioid microphones, usually condensers (though it’s not entirely essential that they be so) to capture a stereo image of the drums from out in the room. Arrange the two mikes in an XY pattern facing the kit (FIG 2). The closeness of the capsules eliminates time arrival differences between the two room mikes, making this array very phase accurate.

Fig. 2: XY Arrangement Of Two Small-Diaphragm Cardioid Microphones

While this arrangement sacrifices a little width in the stereo image (as opposed to that captured by a near-coincident or split pair), the left and right channels will collapse to mono without funky phase issues degrading the sound. If you want a more expansive room sound, you could try a Blumlein array. This is a similar coincident pair technique that simply replaces the cardioid mikes in the XY pattern with bidirectional ones to achieve a broader stereo image and capture even more ambient reflections from all around the room without sacrificing mono compatibility (FIG 3).

Fig. 3: XY Arrangement Of Two Large-Diaphragm Bidirectional Microphones (Blumlein Array)

The boundary microphone, or PZM (pressure zone microphone) as it is often called, is the proverbial fly on the wall of the recording studio. You can opt to use a couple of these little buggers instead of overhead mikes to capture the sound of the room and the brightness of the cymbal wash. These low-profile flat mikes can be mounted to plywood and hung on the wall, or, if the drummer’s back is to a window, they can be taped to the glass about six feet behind and above the player, spaced apart to get a stereo image. If you want to capture more lows, you can try placing a PZM on the floor about six feet or more in front of the kit to pick up more bass drum. Just be sure that the flooring of the room is a hard surface and not carpet.

Customizing A Flawed Room

If the room is on the small side, but has redeeming acoustical qualities, you can make it sound a bit bigger by increasing the distance the sound has to travel before it hits the room mike. Position a large-diaphragm condenser mike so that it’s facing away from the drum kit and pointing up toward a corner of the room (FIG 4). This effectively eliminates direct sounds and captures primarily reflections off the walls.

Fig. 4: A unidirectional mike pointing up at the corner of the room picks up only reflected sound. The sound must thus travel farther before it hits the mike, giving the sonic illusion of a slightly larger room.

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It’s kind of like a bank shot in pool when you deflect the ball off of the opposite edge of the table to drop it into the far side pocket. The fact that the projected sound has to travel to the boundaries of the room and bounce back to where the mike is positioned adds to the distance that the sound has to travel before it reaches the mike. This technique gives the sonic illusion of a slightly larger room.

Now let’s address a common issue: the room presents a harsh sonic environment. It’s your friend’s 10-foot-square cement basement for instance. When faced with this situation, you can do one of two things. You can either come up with some creative room treatments to warm up the reflective surfaces a bit, or try to minimize the sound of the room altogether by deadening the environment.

One way to warm up a cement room is to hang large sheets of plywood or lean them up closely against the walls. This changes the surface characteristics and could help improve the sound quality of the reflections. You could also try hanging a few blankets on sections of the walls to soften and absorb some of the harshness.

If the space is truly terrible, then you’re going to have to go to more extreme measures to make the room disappear altogether. A bad room is a bad room. In order to achieve a good drum sound, you have no choice but to kill all the reflections by using every possible measure available to you: hang packing blankets on the walls, use baffles to absorb sound and enclose the space, and mike the kit closely so you’ll pick up only direct sound without room reflections. So, you might ask, what then about ambience?

The Room Post Facto

Say you end up recording the drums dry because the room was crap and there was no other way. There’s still hope to beef up your sound with the addition of ambience. You can add the room after the fact. Yes, there are two roads you can go by …

The first approach involves a fairly organic method for adding room sound. After you've killed the room reflections and recorded your kit close and tight, create a dry 2-track mix of the drums. Bring this mix to a space with good acoustics, such as the favored wood room with high ceilings or some other sonically pleasing environment. Send the drum mix through a quality speaker in the nice sounding room and record it by placing a mike out in the room to catch the reflections. Add that sound in with your dry mix and viola! It's almost like you recorded the session in that space! This is similar, says Borden, to re-amping a guitar.

The second approach involves a little digital smoke and mirrors to add ambient acoustics sparkle to a dryly recorded kit. You’ve heard of guitarists having the option of shaping their tone with amp modelers, and engineers having microphone modelers available to them. Well, it’s time to give the drummer some! If you have a computer-based recording/digital editing setup, you can use a plug in called a convolution reverb. A convolution reverb is essentially a "room modeler" that can help drummers especially to sweeten up their tone by adding in sampled room acoustics and reverberation.

What convolution reverbs offer are replications of acoustic spaces enhanced with algorithmic reverberation with controllable parameters. A convolution reverb works off of the impulse responses of a room, offering a natural sounding ambience by capturing the response, removing the transient, and adding the decay. It emulates various rooms, allowing you to create the illusion that your drums were recorded some place spiffy instead of, say, your cousin’s garage.

Running a signal through this processor will enhance the sound with the sampled acoustic response and allow you to control various settings in the reverberation. The result is that you have the realism of sampled acoustics and the controls to shape the sound according to your taste. It's more natural sounding than just sending your mix through a synthetic reverb.

There is a number of convolution reverb plug-ins on the market, from inexpensive versions to wallet whoppers with lots of bells and whistles. Generally, depending on the features offered, prices for plug-in packages range between $150 and $2000. Some examples include Wizoo, Altiverb, and the Waves IR-1 Convolution Reverb Series. Digital editing programs that include convolution reverbs include Nuendo, Sonar, and Sony’s Sound Forge among others.

Ambience Mix Tips

Once you’ve captured your room sound and your kit, there are a few things to consider when handling the back end work of putting the whole thing together. Theakston offered several ideas to explore during mix down that involve the clever use of gates, filters, and time alignment of tracks on a digital audio workstation in order to focus the effects of combining room mikes with close mikes on the drums.

The first idea is to use the room track(s) to facilitate a “live reverb” effect for just one or two elements of the drum kit, such as the snare or the toms. Insert a gate on the room mike track(s), and feed the signal from the close mike (on the snare, for instance) to the key input of the gate. This allows the close-mike signal to trigger the opening of the gate on the room mike, letting the room sound through when the snare is hit. Set the release time on the gate long enough to achieve a natural sounding decay. In this way, you get a natural reverb on just that one element for a tighter, more-focused overall sound if that’s what you’re after.

Speaking of focus, combining close-mikes with room mikes can sometimes result in a boomy-ness that could muddy up certain sounds of the drum kit (i.e., the bass drum) and you could lose articulation. In order to fix this problem, try using a high pass filter set at around 100Hz or so on the room mikes to clean up the kick. When setting the roll-off frequency on the filter, however, be sure to not cut so much that it obscures the body of the toms that got picked up by the room mikes.

If you work with Pro Tools, Digital Performer, Nuendo, or some other such program, utilizing the time alignment feature could help clear up definition issues with a drum mix or imbue the mix with a modern pop sound, offers Theakston. The depth of field provided by the room mikes adds distance to the drum sound, but may obscure certain elements of the drum kit under other instruments in the mix. Try moving the room mike track(s) to be in synch with the close mike track(s). Allow about a millisecond per foot, as sound travels at 1,130 feet per second. If the room mikes were eight feet from the drums, move the track eight milliseconds back to align with the close-mikes. This would result in a more instantaneous reverberation, culminating in a more processed sound using real acoustical characteristics to get there as opposed to algorithms in a processor.

This approach works best for straight-ahead, simple patterns by reinforcing the explosiveness of certain drum sounds, such as the snare or the toms. It may not, however, work quite as well for a kit being played with lots of cymbals and fancy tom work because of phase differentials between all the sound sources.

Drums In The House

Now you should have a good idea of how to go about creating a great drum recording by including room ambience into your overall recorded sound. As no situation is acoustically ideal, there are ways to get around the limitations with a little creativity or a bit of help from the miracle of digital plug-ins. Use this information as a starting point and explore options. You could try combining some of the concepts if you’re feeling adventurous.

For instance, the idea of enhancing certain elements of the kit with natural reverb via triggered gates can be combined with the re-amping idea. By creating a dry mix of the kit that augments, say, the snare in particular, and sending that through the speaker to record in a nice space would serve to focus on that one element coming forward and being reinforced by the room. Or you may try running a mix of the drums through a speaker into the drum room while the drums are being recorded. Combining the amplified sound with the acoustic drums will give the recorded kit a super live sound. Remember that the absence of ambience is a sonic signature as well. Mix it up. Be creative, and have fun!