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A New Drum Recording Technique Using Charcoal

By May 28, 2012No Comments

Snares, Toms, and Kick Drum

Drums are available in three main types. We have the kick drum or bass drum. Next, we have the tom and snare. Each drum operates at a different frequency range. Our bass or kick drum starts at 30Hz. and goes through 8,000 Hz. Our tom starts at 50 Hz. and climbs through to 15,000 Hz. The snare begins at 80 Hz. and goes through 15,000 Hz. Each drum has different sounds that are created by these wide frequency ranges of operation.

Attack and Power

Our bass drum has two major sounds that come from it. There is the attack sound and the power sound. The attack sound comes from the beater hitting the drum head. The power stroke or sound is the energy the bass drum produces from resonances inside the drum itself. The attack of the particular drum defines its timing and punch. The thud sound is the power. Jon Bonham of Led Zeppelin had attack and power. Not to many drummers have both or do both well. Jon did. I miss his drumming.

Snare drums have many sounds. The tuning of the snare can effect its sound. How hard the head is struck determines the attack. If a snare has a tight head tuning, one will be able to produce a snap or crack. This is a sound that rock drummers like. If you are recording a ballad, a head that is tuned to a looser setting would produce a more suitable sound.

Toms are a hybrid between kick drums and snares. Their attack sound should be clear and punchy to allow for the harmonics to be recorded at the mic position. There are high toms and low toms. Each produces different sounds because of their respective lengths. Attack sounds on both are the same but the power sound of a low versus high tom is much different due to the length of the tom itself.

Recording Techniques – Up To 4 Mics

How do we record all of these different dynamics produced by the kick, snare, and tom? We need to be able to record the attack and the power of each drum in a manner that allows for these subtle but powerful differences to be recorded. We can use up to 4 mics to try and capture this variance in attack and power of each drum type.

Single Overhead

We use a single, overhead mic in mono. Point the large, diaphragm condenser at the middle of the kit. This is what is termed overhead miking. A smaller diaphragm in the mic will produce a higher frequency sound.

Stereo Overhead

Secondly, we can use two mics and keep them in the same overhead position. This will produce a stereo sound but make sure to use a mic that is the same as the other. Both mics must be frequency matched for good clean and focused stereo image to occur.

Three Mics

Next, we can use three microphones in an overhead configuration and then place the third mic, a small diaphragm condenser on the bass or kick room.

Four Mics

With four mics, we need a large diaphragm condenser for the kick drum. We will place this mic inside the bass drum. Point the mic at the beater to drum impact spot. Place one mic on the snare and two overhead in a stereo configuration.

Low Frequency Resonances

With all of the above microphone techniques at our disposal, we have to consider the room sound in the room in which the mics are placed and the recording is to be made. The room with drums and their ability to generate low frequencies will produce resonances within the room. If these room resonances bleed into the microphone position and into the recording. This will cause blurring and smearing in the recording and there is no way you will ever be able to remove it from the mix with EQ.

Our drum sound is a combination of attack and power. The attack can be heightened and the power can be made to sound larger by using less of it. If we use sound absorption at and around the mic position, we can reduce pressure levels from resonances in the room at the mic position. We can also reduce pressure levels at the microphone position by using sound absorption technology. Reduced sound pressure means more sound in our recordings.

Need Sound Absorbers

To achieve the necessary rates and levels of absorption to reduce low frequency pressure levels at the microphone position and in the room, we must use low frequency absorption that has the power to reduce pressure levels significantly, so our microphones can pick up more sound energy at the microphone position. We need absorbers that absorb room resonances and the pressure levels from a powerful source such as a kick drum. Low frequency absorbers currently in the marketplace do not do this. One needs a more powerful low frequency sponge with drums in a room.

Activated Carbon / Diaphragmatic Absorption

If you take a diaphragmatic absorber and calculate the resonance frequency needed in the room and at the mic position, you can build an absorber that has the necessary rates and levels required for this mic technique. However, you will have to use an internal cabinet fill of activated carbon or charcoal inside the diaphragmatic absorber, you will increase the efficiency of the diaphragmatic absorber. Charcoal will lower the cabinet’s Q value to a point that the diaphragmatic absorber will function at a much lower resonant frequency and at much higher rates and levels of absorption. These lower levels and higher absorption rates produced by the activated carbon inside the absorber will reduce pressure levels fast, so our mics can “hear” more sound.

Room Resonances

Walk around the room and place your absorbers at the areas of highest sound pressure. If you need a Db meter, use it and walk around the room as music is playing. You will see the pressure increases on the meter. This is the spot to place an absorber. Place an absorber directly in front of the kick drum or directly behind the microphone. Place an absorber on both sides of the microphone at the opening of the kick drum. You can try placing a absorber between the drummer and the wall.

Use these activated carbon (charcoal) absorbers next to the snares and toms. Try placing them under both or to the side of the snare or tom. Experiment with different absorber positions to achieve different sounds. Don’t forget about the room resonances. They will be present with snares and toms just as they are with the kick drum.

Reducing low frequency sound pressure reduces resonances and provides for a cleaner and tighter bass in our recordings. Taming resonance through powerful, activated carbon, absorbers allows for more of the true sound signal to get into and through our microphones. Less sound pressure levels at the mic position allows for the harmonics and overtones to be heard and not covered and smeared.


Author MikeSorensen

I am a structural engineer as well as a master furniture maker. I design cabinets for low frequency, activated carbon absorbers. Connect with me on Google+

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