articles & reviews

Drum Physics
By Greg Gaylord (Music Market June1996)

Energy is absorbed as it passes through multiple layers. An insulated house is an example of this. Heat and cold do not pass as quickly through all those layers of different materials (siding, sheet rock, insulation, etc.) as it would through a single layer. Most drums, 1 and many snare drums on the market today, are made in layers. There is a layer of adhesive, often urea formaldehyde which is a plastic resin, between the wood plies. This absorbs some of the energy of the drum as it passes through the shell. Layers also absorb higher frequencies, while lower frequencies pass through. This effect can be heard outside a night club. You will hear the low frequencies, such as the bass drum, more clearly than that of high frequencies.

This same concept applies to drum heads. Multiple layer heads such as Remo's "Pinstripe" will be more muffled than a single layer "Ambassador." Drum heads with dots also offer a muffling of the fundamental frequency, which is focused at the center of the head.

When we strike a drum, several different frequencies occur. The "fundamental" is the base frequency of these sounds. To see an example of this, we need only pluck a stringed instrument. A fundamental will be produced simultaneously with higher frequencies.

Drummers seem to be drawn to drums with greater resonance, especially snare drums. We only need to look at the popularity of single ply snares, which have greater projection and volume than multiple ply snares, for this to become apparent. Reinforcement rings are necessary to keep a single ply drum round but also "choke" the drum. There are now custom drum makers, like myself, offering "segment" shells which offer even more "sound" than a single-ply shell because the need for the reinforcement hoop has been eliminated.

Many drum companies are using a system of mounting shell hardware which they claim will have the least interference with shell resonance. The idea is that by mounting the lugs at certain points on the shell, vibrations can pass more freely than at other points. The point where there is minimum vibration is a "node."

The node is the basis for mallet instruments such as the marimba and vibraphone. On these bars is a point from which the bar can be supported, allowing it to vibrate freely. This point is 22.5% of the total length, from either end. For example, if our bar is 10 inches long, the point would be 21/4 inches from each end.

You can try this with some wood; it does have to be symmetrical. Place a mark on the wood indicating the node point. Then hold the wood with two fingers at one end and listen to the wood as your other hand hits it. It will sound choked. As you move your fingers closer to the mark on the wood, you should notice an increase in its resonance.

Certain drum companies have taken this concept and applied it to drums. The "bar" of wood is then bent into a circle, which now no longer has the end points as before. Now, instead of the points running lengthwise, these companies claim the points now run the depth of the shell.

I have tried to hear this with one of my segment shells. I must admit that my ear is not good, and I was unable to hear any difference as I approached the "magical" point. Perhaps electronics are required to hear the difference.

If you try this for yourself, don't strike the shell at a "dead spot." Suspending the drum with one finger in the middle of the shell at a 12 o'clock position will produce dead spots in the 3, 6 and 9 o'clock positions.

Robert Gatzen, a mallet player, is the inventor of the nodal point mounting system for which Nobel and Cooley (N&C) have patent rights. N&C in turn licenses this system to companies such as Mapex and Yamaha. The patent is on the concept of a low mass system mounted at 22.5% of the drum's depth from the bearing edge.

I spoke with Bob who told me that his concept did originate from the vibraphone. He originally started his quest for a better sounding drum by using a two-post mounting system (like a tube lug), which then progressed to a one-post lug mounted in the center of the drum. The next step in the evolution was the one post bottom mount at the 22.5% distance.

I asked Bob how he tested these drums. He said electronics were used in conjunction with averaging. Because of the intricacies of drums and the difficulty in control of variables such as head tension, where the head is struck and how hard it is struck, the only way they could get reliable results was to use the averages of a drum's performance. Bob also mentioned that he would like to see further research done which might yield more information.

I am not convinced that this concept for mounting hardware transfers from a bar with end pints to a circular shell where these end points run together, nor am I convinced that these points can suddenly change position from horizontal to vertical when bent into a shell. I do remain open, however, because I do not think other companies such as Yamaha would be using it on their Maple Custom if there wasn't something to it. HHHHMMMM

Bob and I do agree that, in order for the industry to move forward, the drummer must demand better overall quality, not simply settle for the glitz of gold lugs and choice of a bajillion finishes. If a drummer understands how a drum works, perhaps drum companies will focus less on glitz and more on precision drum making.

Tuning drums is a first step in learning how a drum works. Bob has a video out on DCI called Drum Tuning/Sound & Design which addresses this topic.

I would like to thank Bob Gatzen for his assistance and to commend him or his sincerity and desire to improve the drum industry.

If you have any comments, additions or corrections (I'm only human), please write to me care of Bay Area Music Market Magazine.