Drum shell Construction
This section is based on the excellent article by Mike Radcliffe on drumdojo.com
It sets out to explain how the physical characteristics
of a drum's shell affect the sound of a drum. The drumhead combines with the physical characteristics of the shell and the tuning standard adopted to determine the overall tonality of the instrument
A drumshell designed for maximum
resonance, will be affected by a drumhead combination designed to
muffle of a tuning designed to deliver a pitch bend, or decreased sustain. Muffling is not recommended as it overrides a large part of the drum's physical design and the head selection.
We gratefully acknowledge Gene Okamoto and David Howe of Pearl Drums for their permission to use information from their web site for this page. www.pearldrums.com
Why are
drum shells made of wood?
There isn't a special reason other than wood sounds nice and because there and almost infinite variations and combinations available .
There are some companies making drums out of plastics, metals and composites, we will focus on wood. Which material sounds the best is at best subjective, but since the vast
majority of drums are made of wood, we will focus on that.
Generally, the more dense the wood, the better it sounds because it will vibrate more 'evenly' helping to create even tones when struck or during coupled
vibration, as with a drumhead. There are all kinds of exotic hardwoods 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 available sufficient quantity; to be workable, it have a long, straight,
tight grain, with no knots. It must be dense enough to be 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 pore
structure that is pleasing to the eye and takes stain well.
Examples of woods that fit these categories are Maple, Birch, Beech, Poplar, Ash, and
Mahogany (or Lauan). There are different species of these grown in
different areas of the world. Each will have differing characteristics, but
still close enough to be grouped under their 'main' names. i.e.: We won't
be differentiating between Canadian Rock maple and Birdseye maple, or
between Scandinavian birch and any other birch.
Maple,
Birch, and Lauan.
Most
drum shells are made of one of these three types of woods, so we can compare them.
Lauan is
the softest and least expensive of these woods, it is also the least attractive. For this reason it is
often used in low end, budget drums and most
lauan drums will be covered in a plastic wrap. This also makes them less expensive to
make.
Maple and Birch are commonly used to make high end mass produced drums. They both
sound wonderful and look very attractive with a natural finish. One of the reasons why maple is so popular with drum
makers is because it is the choice of Keller who specialise in making drum shells. Many big name 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.
Maple, Birch and Lauan have different tonal characteristics.
The diagrams below were provided by Gene
Okamoto and the folks at Pearl Drums.
Most companies use Lauan for
their Mahogany shells. This is not the same African
Mahogany that Pearl refers to in these diagrams, but a much cheaper, less
attractive, and less tonally pleasing species.
Boosted lows - smooth mid and high frequencies - Good for all
around applications.
Boosted high frequencies - slightly reduced mids - low end boost
Very rich low end frequencies - smooth mids and a good balanced high end - warm sounding "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.
Any of these
woods, with the exception the lauan that budget drums are made of, will produce
a wonderful tone that is slightly different from the others. Notice how we do not say better or worse - it's very much a personal preference. If you have certain preferences about the frequency
response for your drums, choose accordingly.
Shell
Thickness
Thicker shells have higher pitches. Thinner shells have lower pitches
Don't get caught up in the number of plies because ply thicknesses can vary greatly. Density of the wood can determine how thin a ply can be cut. Lauan plies will be much thicker than
Birch, for example, because Birch is stronger and can be cut thinner.
Making
shells from plies, instead of solicwood adds strength and
stability to the shell. Ply alternates the grain of each layer so that a thin shell
can be made that is stronger than a thicker, solid piece of wood. Ply construction also resists warping.
Pearl Drums, provided the following information about how shell
thickness affects the sound of a drum: The number of plies affects how 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) facilitate 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. Great for recording .
Medium thick shells (6 ply, 7.5mm) greater stiffness and resistance
to energy transfer from the heads. Less shell vibration brings a less warm sound but projection is
greater. 'Standard' drums approximate this thickness.
Thick shells (8 ply, 10mm and 10 ply, 12.5mm) "Efficient", allowing most of the player's energy to be focused to the audience and not into the shell.
Snares 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. Occasionally you will see depth x diameter; that MO is somewhat unusual but be watchful. Larger diameter drums give the potential for lower tunings and greater amplitude (volume).
Shell depth also affects
tone with deeper shells emphasising lower frequencies. However depth also affects 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. As an example, power toms became popular in the 70's for rock music, low tuned deep toms delivering projection and low end thud. This is also
why smaller drums with higher tunings are so popular with jazz music adn they help deliver cleaner, fundamental tones.
-Mike-
Edited by Paul Marshall
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