We continue with the series of articles on the great art of acoustically recording different instruments, in this case with the one dedicated to drums, which we began last month. In the previous issue we discussed in depth the vital importance of drum tuning, the placement of the instrument in the recording room and the different approaches to miking (stereo pair, multi-mic or a mix of both), as well as the most important characteristics of any mic (frequency response and polar pattern).

In almost any musical style, at least 80% of the importance of the groove created by the drummer lies in the use of the bass drum (BD), the snare (SD) and the hi-hat (HH). If the sound capture of these three elements is right, success is guaranteed. In this article we'll focus on multi-mic recording of these three elements.

MULTI-MIC RECORDING
We've decided to record the drums with at least one microphone for each of its elements. With this approach we aim to keep the signal of each one as isolated as possible so that we can process them in depth in the later mixing stage. Find out how to get the most out of it.

BASS DRUM (BD)
This element of the drum kit produces the lowest signals of the entire kit. The fundamental frequencies generated by the BD are usually between 80 and 130 Hz, although obviously we have signal from 40 Hz upward and, depending on how we place the mic(s), with greater or lesser intensity. In your BD recording, which frequency is the fundamental?

Let's imagine our BD generates 120 Hz as its fundamental frequency. It turns out that this frequency doesn't fully develop until 2.83 m. Does this mean I have to place the mic at that distance? No, but you do need to bear it in mind.

If we use two microphones for the BD, we can put one of them inside to capture the attack of the sound and place another outside to capture the body (lows) of the sound at a distance of 0.7 m, 2.1 m or 2.8 m. We'll choose 0.7 m (maximum intensity). And we'll use our ears to check whether the result is right. The Audix D6 microphone is an excellent candidate for this job because, in addition, it has a somewhat tighter polar pattern than is usual in BD mics, so we can place it outside without fear of other sounds leaking into it at excessive levels. Inside, great candidates are the AKG 112, the Beyerdynamic TGX50 or the Sennheiser E602, all dynamic mics, possibly a better option than condensers, especially in pop, rock or hard rock styles. For subtler styles we can indeed use condenser mics.

The further we put the microphone inside the BD, closer to the head that the BD pedal strikes, the more attack we'll get, with less body. If we need a compromise between attack and body, we can angle this inside mic so that it doesn't point directly at the head but slightly toward the shell of the bass drum. Small position adjustments will give us great results before we rush to the console EQ. When using two mics, blending them will be vital to getting the sound we're after. And let's keep in mind the phase relationship between the two signals.
Other ways of capturing a BD include using Yamaha's SUBKICK or a woofer acting as a microphone. Using a boundary mic like the Shure SM91 to minimize outside influences is also a good idea.
Useful frequency areas to start with might be: small cuts around 450 Hz, trying to tame the "cardboard box" sound; the presence of the pedal beater can be found between 2 and 3 kHz, and we can cut almost everything above 5 kHz, since it has nothing to do with the natural sound of this element of the drum kit.

An important note is whether we want or plan to trigger samples with a sampler or software sampler. To combine them with the original sound, we'll need a sound that is as little influenced as possible by the other elements of the kit, so that the sampler responds properly.

SNARE (SD)
The other king of the drum kit, the snare. Possibly the element that best defines the character of the song we're going to record. A classic mic for capturing this element is the Shure SM57. The AKG 451 (condenser) is also a very good option. With a drummer who has a clear, defined and consistent attack on the snare, and a snare sound balanced between the tension of the top head, bottom head and snare wires, a single microphone is often enough. We must place it where it won't get in the way of the performance. If we have an inconsistent drummer, placement is critical so as not to ruin the mic with a stray stick hit. The ideal starting position is to bring the head of the SM57 two finger-widths in from the rim and two finger-widths above it, all pointing at the center of the head, where the stick strikes. Here we get a fuller presence of harmonics and, using a cardioid mic, thanks to the proximity effect, we get more body in the sound.

We need to consider whether rimshots or cross-stick will be played in the song, since that kind of playing has a completely different timbre from the snare played normally. Faced with this, we can consider several solutions:
a) Have a different mic for this capture.
b) Split the recording of the song into two parts according to the difference in playing, if possible.

If we think we'll need to change the timbre of the snare in the mix, or at least want to keep as many options recorded as possible, the best option is to place a mic underneath as well, pointing at the snare wires. Again, another SM57 underneath is a good choice. We must take into account the phase between the two mics, since they point in opposite directions, and the distance between them.

Whenever possible, we should place the mics on the same vertical axis; otherwise the phase will also be affected. The best option, in any case, is to record some tests and see in our DAW how the takes from these two mics behave in terms of phase, and act accordingly.

HI-HAT (HH)
We can start thinking about a high-pass filter on this channel, since there is practically no HH sound below 150-200 Hz, and this way we'll partly minimize the BD bleed and the SD attack.

A condenser mic is an ideal choice. For example, an AKG 451 with a CK8-type hypercardioid half-shotgun capsule has a very natural sound without harshness, something very common when miking the HH.

The placement of the chosen mic should take advantage of the horizontal plane of the HH's top cymbal as an element that minimizes the snare sound in this mic. We should avoid the area where the two cymbals clash, with the outer edge being the most suitable area for placing the mic, although the lower outer part can also be optimal. The distance can vary from a hand's width to half a meter, depending on the drummer's playing.

A vital aspect when miking these three elements is not only to look at and position the mics as well as possible for each element but also to consider how much of each element leaks into the other mics.

In the case of the BD, how much SD level do we have in it?
In the case of the SD, how much BD and HH level do we have in it?
In the case of the HH, how much BD and SD level do we have in it?

With this idea in mind, we'll most likely keep moving the mics until we get not only the best sound from each one but also maximum isolation between each element.

ALWAYS
You should always take any advice we can give as introductory, because the variables are almost infinite. The musical style, the type of instrument, the musician, the room, the miking, the signal routing, the recording system and technique, the processing before or after (EQ, compression, etc.) that affects the signal, the musical arrangement and the experience of the musician and the engineer are some of the parameters that will make the difference in the quality of recordings.

NEVER
Never take the advice you may read or receive as the one and only truth, no matter who gives it to you. Even temperature or humidity can change a recording from one day to the next. However, experiment by starting the process from the advice you receive, trying to draw conclusions in the short, medium and long term.

How do I find out the fundamental frequency of the sound I'm capturing?
We have several options:
1.- If you use Cubase: Audio menu / Spectrum Analyzer
2.- Free plug-in: Voxengo SPAN in VST and AU formats for PC and Mac
3.- Commercial plug-in: Waves PAZ Frequency (Mono/Stereo)

Select a portion of your previously recorded sound and analyze it. Draw conclusions from it.

How do I find out the wavelength of a frequency?
It's very important to know the wavelength of a frequency, because this will tell us how to position the mics. It's that simple:

Divide 340 by the frequency whose wavelength you want to know. For example, 120 Hz.

340 / 120 = 2.83 m

340 (m/s) is the average speed of sound traveling through air. This value isn't constant; it varies with air temperature. Even so, 340 m/s is taken as the default

Sound capture process before recording
As you can see, placing mics on the elements of the drum kit can easily take us several hours if we follow all these steps: we place the mics, check that we have the most suitable signal in intensity and tone, record some samples of each element, listen to them, analyze them, draw conclusions, move the mics based on those conclusions, record some samples of each element again, listen to them, analyze them, draw conclusions, move the mics based on those conclusions...