Cool acoustic tricks to obtain massive kick sounds
By Eric Ferguson
The great thing about the art of recording is that there are no rules. Recording is not rocket science and we are not piloting passenger-stuffed 747s. Whether a trade or hobby, recording should be fun and its goal should be capturing fabulous-sounding creative moments.
To me, this translates into two important mantras. One, whether you are amateur or professional, experimentation should rule over protocol. Two, professionals don’t always know best, so a constant dialogue between engineers at all levels is important to spread knowledge and advance our art.
Elsewhere in this online library, I have written about various drum recording techniques I’ve discovered or been taught. One tip, though, came from Mr. Derrick Davis, a reader of Recording, and I felt it was worth its own article.
Derrick suggested rolling up a long carpet into a tube, and placing it directly in front of the kick drum. The tube’s diameter can vary from approximately 1 foot to the size of the drum. At the far end Derrick recommends placing a large-diaphragm condenser mic such as a Neumann U 87 or Roswell Pro Audio Mini K47. After covering the open end of the carpet with blankets for leakage control, Derrick reports you will happily discover a kick with a huge low end.
This is a great suggestion and I witnessed this technique myself several years ago when assisting another engineer. One principle behind this method is that generally you get increased low end the further you move a mic out from a kick. This phenomenon only really works in the first foot or so, in an area known as the “near field.” Derrick was probably not capturing this bass boost, though, as he suggested using a carpet as long as ten feet. I suspect Derrick was experiencing resonance and filtering from the tube, much like what you hear when you shout through a pipe or paper towel roll.
When moving the kick mic out of the drum, either into the open or into a tube, a loss of attack and an increase in leakage usually occurs. Most pros compensate for the attack issue by using two mics: one inside the drum aiming at the beater to capture the snap, and another outside the drum for the more “developed” bass-rich sound.
The carpet technique is an extension to this two-mic method. With the added isolation of the carpet, you can now move the outside mic even farther from the drum and further increase the low end. By experimenting with distance, you can now experiment with mic distance, finding the ideal position without worrying about leakage.
Unfortunately, my experience has shown that there are several major logistical difficulties to this carpet technique, the most obvious being the question of how to keep a heavy carpet in a tube-like shape between the drum and the microphone. Mic stands can be used for stability, and shorter or lighter carpets can be used, but it’s usually pretty cumbersome. Another caveat to the carpet method is the extra space it requires. This may not be an issue if you are lucky and working in a large room, but many home studios do not have the space for a 15-foot drum set!
Oddly enough, for me the biggest disadvantage to working with the carpet is the extra time it requires. While we must constantly experiment and enjoy our time recording, we do need to think about the needs of our clients. Musicians and producers are usually pretty patient with experimentation, but nobody likes waiting hours for the engineer to dial in the perfect bass drum sound. We must ultimately serve the needs of the music and sometimes this means letting go of our quest for sonic supremacy.
A variation on this carpet idea, one I’ve seen commonly in professional studios, is to use packing blankets instead of carpet. Packing blankets are much lighter than carpet, and more flexible and faster to place—a couple of boom mic stands can easily support a blanket “tent.” Most pros build the “tent” out several feet from the drum and use a large-diaphragm condenser mic to capture the “near field” boost. Be sure to seal off the tent to prevent leakage.
If needed, use gaffer’s tape (the ultimate studio savior and worth the extra cost over duct tape) to help the mic stands better hold the blankets. I often use gaff tape to secure the blankets to the drum hardware, but I never stick it on the shell. Gaff tape is easily removable from metal, without the gunk left behind by duct tape, but I don’t want to risk scarring the wood shell of a vintage bass drum. Never use duct tape and always ask the drummer first!
One important side effect of these techniques is the timing/phase difference caused by the distance between the mic inside the kick and the mic at the end of the tube or tent. Since sound travels at roughly 1000 feet per second, two kick drum mics five feet apart have an approximate five-millisecond difference in timing. When these two mics are mixed together, serious phase cancellation can occur and you could potentially lose some of the precious low end for which you originally built the tube or tent in the first place.
When tracking, be sure to compare the faraway mic’s polarity by flipping your console or mic pre’s phase/polarity switch. When mixing in a digital audio workstation, I usually go one step further and slide the far mic’s track earlier to perfectly match the timing of the inside-the-drum mic. Obviously, this technique requires that you record the two mics to separate tracks. While I often mix multiple snare mics together, the distance inherent in the carpet/blanket technique necessitates separate tracks.
An old adage that I frequently quote is that all engineers want to be drummers and all drummers want to be engineers. The complexity of multi-mic recording, the overwhelming power and symbolism of drums, the importance of the surrounding space, and the great variation in drum tone creates a symbiotic relationship between drummer and engineer. This breeds mutual experimentation, and new techniques are constantly born.
Remember: Low end is your friend!