Drum Shells

This section will attempt to explain how the physical characteristics of a drum shell effect the sound of a drum. Please take into consideration all the things explained in the drumhead section, when contemplating all this. Also keep in mind that the when making the following comparisons, there has been no consideration for what type of head is being used. In other words, it's all relative. A drum shell with physical characteristics causing it to have maximum resonance, will of course be offset by a drumhead combination designed to muffle. Get it?

I would like to give credit to Gene Okamoto and David Howe of Pearl Drums for giving permission to use information from their web site for this page. If you want to check out their site, it's at: pearldrum.com

Why are drum shells made of wood?

Got me? No really, there isn't a special reason, other than wood sounds nice. As in other musical instruments, wood just has the kind of characteristics that lend it to producing a pleasant tone. Other materials are used for making musical instruments; metal, bamboo, plastic. But for certain instruments, wood is just the material of choice. I mean, we've had a several hundred years to figure it out, right?
Although there are some companies making drums out of plastic and metal, we will focus on wood. It can be argued what material sounds the best, but since the vast majority of drums are made of wood, we will focus on that.

I will say that, in general, the harder the wood, the better it sounds. The harder and more dense a material, the more evenly it will vibrate. When it vibrates evenly and as a whole, it helps to create even tones when struck or during coupled vibration, as with a drumhead. There are all kinds of exotic hardwoods in the world and many of them are harder than what is generally used. But in order for a wood to be considered economically feasible for mass production, it must be inexpensive, workable, and attractive. To be inexpensive, a wood must be in great quantity in the world. To be workable, a wood must have a long, straight, tight grain, with few knots. It must also be dense enough to be hard and strong, but not so dense that it can not be bent into a circle. To be attractive, it must have the same characteristics as for being workable, as well as a pour structure that is pleasing to the eye and takes stain well.

Some woods that fit these categories are Maple, Birch, Beech, Poplar, Ash, and Mahogany (or Luan). There are different species of each of these, grown in different areas of the world. Each will have differing characteristics, but still close enough to be thrown in with their respective names. ie: We won't be differentiating between Canadian Rock maple and any other kind of maple, or between Scandinavian birch and any other birch. Many low end drums are made of wood such as eucalyptus, basswood, tulipwood. Some companies combine these woods with Maple or Birch outer plies. Since these woods are not very tonally pleasing, and are only used to lower the cost of the drum, at the sacrifice of the sound, we won't get into them.

Maple, Birch, and Luan.

Most drum shells are made of one of these woods, so we will compare them. Luan is the softest of these woods and it is also the least attractive, which contributes to it being the least expensive of the three. For this reason it is often used in low end, budget drums. Because it is relatively unattractive, most luan drums will be covered in a plastic. This also makes them less expensive to make, because a plastic wrap far less labor intensive than a spray finish.
Maple and Birch are what is used to make most high end drums. The choice between these drums is really a matter of personal opinion. They both sound wonderful and look very attractive with a natural finish. One little secret though: one of the reasons why maple is so popular with American drum makers is because it is the choice of Robert Keller. I won't mention any names, but many, many American drum makers buy their shells from the Keller company. There is nothing wrong with this. Keller makes beautiful shells and they've been doing it for more than 50 years, so I think they've got it down.

But Maple, Birch and Luan each have different tonal characteristics, so lets take a look at those.
The diagrams below were provided by Gene Okamoto and the folks at Pearl Drums. Keep in mind that what most companies are using for their Mahogany shells, that we refer to as Luan, is not the same African Mahogany that Pearl is referring to in these diagrams, but a much cheaper, less attractive, and less tonally pleasing species.

Slightly boosted lows with smooth
mid and high frequencies for all
around applications.

Boosted high frequencies, slightly
reduced mids, and a good low end
punch for applications requiring
extra presence and cut.

Extremely rich low end frequencies,
with beautifully smooth mids and a
slight roll-off in the higher frequencies
for applications requiring ultimate
"bottom" and punch.

Many people describe Maple as being "warm" and even in its frequency response. Birch is often described as "bright," because it produces more high end than Maple. The bottom line is, like most musicians, we can get pretty anal about our equipment. Because of this, we hear minute little differences that most normal people would never distinguish. Any of these woods, with the exception the luan that budget drums are made of, will produce an equally wonderful tone. If you have certain preferences about the frequency response for your drums, choose accordingly.

Shell Thickness

In a nutshell, the thicker the shell, the more higher it will sound. The thinner the shell, the lower it will sound.
Don't get caught up in plies. You can't always judge a shell's thickness by how many plies it has. Some companies cut their plies thinner or thicker than others. The density of the wood also determines how thin a ply can be cut. Luan plies will be much thicker than Birch, for example, because Birch is stronger and can be cut thinner. Or one company's 9 ply shell could be thinner than another company's 6 ply shell. There are many variables.

Making shells from many plies, instead of one thick piece of wood, adds strength and stability to the shell. By alternating the grain of each ply, a thinner shell can be made that ends up being stronger than a thicker, solid piece of wood. It also will resist warping, as each ply has a different direction to the grain.

Gene Okamoto at Pearl Drums, provided the following diagrams about how shell thickness effects the sound of a drum:

The number of plies effects how readily energy is transferred from the
heads to the shell. This single factor has a profound effect on the tonal
characteristics and projection of the drum.

Thin shells (4 ply, 5mm) enable relatively easy energy transfer from the
heads to the shells thus causing the shells to vibrate. This vibration
imparts a very rich "wood" tone to the overall sound that can be most
appreciated in near-field applications and especially in recording.

Medium thick shells (6 ply, 7.5mm) have greater stiffness and resist
energy transference from the heads. With less shell vibration, a trade-off
is achieved: the sound is slightly "cooler" than thinner shells but
projection is greater. Drums made to this thickness are ideal for
general-purpose applications and / or situations requiring more

Thick shells (8 ply, 10mm and 10 ply, 12.5mm) are extremely "efficient"
and allow most of the player's energy to be focused to the audience. These
drums are ideal for coliseum-type venues and other applications requiring
high sound pressure levels. Snare drums made in this thickness rival metal
snare drums in intensity and projection.

Shell Sizes

The size of a shell is measured in diameter by depth. A 14 inch snare, with a depth of 5 and 1/2 inches would be notated as: 14x5-1/2 (5.5). A 12 inch tom that is 10 inches deep would be: 12x10. (Some companies reverse this notation, but we won't raise a fuss.)

We all know that the bigger the diameter of a drum, the deeper it will sound. For example: a 16 inch floor tom sounds much lower than a 12 inch tom. The depth of the shell also effects the tone, as well. The deeper the shell, the lower the sound and vice versa. But the depth effects more than the tone of a drum. A deeper drum will also be louder and therefore project more. A shallow drum won't project as well, but it will have better resonance and a purer tone. This is why power toms became so popular in the 70's, for rock music-- projection and low end thud. This is also why smaller drums are so popular with jazz music-- cleaner, fundamental tones.

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