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Small option:
Here the drive unit will be unable to move large amounts of air instantaneously, because in order to
move any real volume of air, the small diaphragm will need to travel a long distance to make up for
its small size. This pumping action will be incapable of reproducing the explosive timpani. The main
benefit of this design comes from the relatively small sound signature from the cabinet. However the
small volume of air available will create a strong spring effect on the moving parts that will elevate
the resonant frequency of the drive unit, severely limiting its ability to produce energy below 35
Hertz.
Large option:
Making the parts larger confounds the designer in a different way because the large diaphragm
becomes more difficult to control, so stiffer suspensions are needed. These stiff suspensions
elevate the resonant frequency of the drive unit. What follows is a balancing act between adding
mass to the diaphragm to lower the resonant frequency and the Stiffness of the suspension. Both
these options impact upon the movement of the coil thought the air gap. This often requires
increases in the air gap and consequential decline in power. There are severe limits here also, due
to the inexpensive drop forged components and ceramic magnets that are used almost without
exception in the vast majority of Woofers.
THE WEAKEST LINK
The most important problem that is accepted without exception in every sub woofer is in fact the
woofer itself. Although large diaphragm systems are commonly accepted, it is easy to demonstrate
that they cannot integrate with the fast small drive units used to reproduce the mid range sound
energy. The laws of physics dictate that you cannot accelerate and decelerate large systems like
you can small ones. Woofer designers have attempted to reduce the problems by using stiff
suspensions, and in some cases doubling the numbers deployed, in order to provide the restoring
force to the diaphragm. This solution defeats the dynamic capabilities even more! The problems do
not end here. The next major compromise of the woofer, is its dependence upon the external
structure. The Woofer is of course attached directly to the external structure. The huge forces
injected into this structure cause massive sympathetic resonance’s that are clearly audible and
impact directly upon the sound that is heard. As the cabinet increases in size, so do the resonance
problems. In fact it must be accepted that there will be an exponential increase in cabinet
resonance’s.
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