I have seen many different drum rooms lately. All have been “small” rooms. A small drum room is a room with only an 8′ ceiling height. Of course, there are other variables to consider, but when I see drums set up in rooms with 8′ or less ceilings, I know how the drums will sound in the mix. The drums will have a small room sound attached to the snare,tom, and kick. We all know this sound and none of us want it. We want our small drum rooms to sound like they were recorded in rooms that have 25′ ceilings. Can we do that? Maybe, lets look at drum sound production process in small rooms.
Our drums are vibrating diaphragms that move energy into the air. This energy is generated from a vibrating membrane that we cause to vibrate by striking it with objects. Not any objects, but mainly wood or metal sticks, sticks with rubber pads, and a mallet with padding that we strike the kick drum with by “kicking” or pushing down on a pedal that is attached to the striker with our foot.
This striking motion and the other sonic artifacts on our kick drum has three sound components to it. The first sound is the actual drum surface/mallet head contact strike. We can hear that sound and we hear it first in the series of three. Obviously, I have slowed this process down, so we could look at it more carefully. After the strike sound, we have the drum itself resonating. It will resonant for us starting at 30 cycles and moving up through. The drum sound itself is the largest sound part.
Bass Drum Sound
It is the sound of the source itself generating its energy into the room space. It is powerful with the attack strike and the drum resonances together. the striker and drum sound merge together to form a certain sound. Since they are different sounds and a quality drum room must allow for both sounds to be heard clearly, we must now look at the third source sound.
The third sound in our trilogy is the room sound. The striker contact, the drum itself, and now both of those energies are released into the room itself and must now interact with the existing room to produce a certain sound. This will be your drum room sound. If our room is small, we must find away for the microphone to be able to receive all three different sound energies; striker, drum, and room. In a small room, it is not possible for the room sound to develop properly because the room is to busy shaking itself apart. We need to look at the distribution of pressure in our small room.
Large Bass Driver
In a small room, with a 24″ in diameter kick drum, we have, in essence, a bass driver speaker with a 2′ diameter. Think about having a set of speakers that had 24″ bass drivers. The only way for those speakers to breathe properly is in a large room. They would destroy a small room by creating so much energy that the room walls would go diaphragmatic and start moving. Large sheets of any building type material that is moving as a result of air born energy striking its surface is not a good idea in any room let alone a drum room. Once this vibrational energy reaches a certain level, the room walls will start sounding off on their own. We don’t want that.
The microphone is very close to the kick drum and can “hear” the striker attack and the drum sound from the resonating drum cavity. Sometimes, I think the microphone is too close to the bass drum, but that is another discussion for another day. Our microphone can “hear” the strike and drum, but in a small room scenario, the room sound is covered and smothered from the original microphone or any others placed within the room. This smothering is caused by too much energy within the small room and the room complaining about all of this overcrowding by producing resonances.
What if we reduce the resonances down to a level that does not affect our room sound quality. This is not easy because we must use low frequency absorption technology that needs mass to perform. We must also make the room physically smaller by placing low frequency absorption technology at certain places in the room. In small drum rooms, low frequency absorption technology must be placed everywhere, not just the corners and then we will still have issues because of the original room size. We are making the room physically smaller to make it sound larger?
Reduce Pressure At Source
What if we reduced the pressure levels, not in the whole room, but just in the highest pressure areas. The highest pressure areas are around the drums themselves. If we saw a pressure map of the drums and the immediate vicinity around them, we could place the right type of sound sponge if you will to absorb pressure as it begins to enter the room. With reduced pressure at the microphone position, we allow for the microphone to hear more clearly and this clarity would be translated into the microphone.
Large Sound Sponges
The low frequency sound absorbing technology within our sound sponges must be able to handle large amounts of energy and absorb that energy at the right rate and level. This is too big of a job for foam. The bass absorber chosen must be able to absorb down to 30 cycles and up and do so in a large fashion. Not 6-10 sabins at 30 Hz. but 30, 40, and greater. The “sponge” must be easy to position around the microphone and drum area. It must be mobile because different room dimensions produce different pressure maps and one must be able through experimentation, to find the correct number and sponge positions needed to achieve our sonic pressure reductions at the microphone position.
Reduce Pressure Levels
If we reduce the pressure levels around the microphone, we will be able to hear more of the actual drum resonances and it is these energies that are full of our drum dynamics and drum harmonics. If we can clearly hear all drum dynamics and the associated harmonics at the microphone position, we are on our way to a bigger drum sound within our small room.
If we define dynamics, separate them, and then give the harmonics time to form properly and I do mean literally more time through less pressure in the drum area, we can produce a sound that when mixed with the room produces a final analog signal for our ears to pick up that has with more information in it. Not in all cases, but it is so in this case, that more sound heard is bigger sound made.
We all know what big drums sound like