AUDIO MYTHS
Myths are often powerful metaphors
illustrating the darker byways of the human condition. Sometimes, as in urban
myths, they are exaggerations or downright fabrications that are passed on in
the belief that they are true. In the world of audio we have our share of
myths; here they are often based on partly or entirely misunderstood items of
technical information.
Take a recent story I heard. Bass players
cannot hear themselves on stage because the wavelength of bass notes is 32
feet, so to hear the bass you must be 32 feet away from the amplifier. Where to
start?! There are so many flaws in this story that one almost feels embarrassed
to start in on it, but it is loosely based on something related to the reality
of the situation.
32 feet is around the wavelength of the C
below the bottom E string of most bass guitars. If we assume that the bass
player never ventures further up the finger board than the 5th fret,
he or she can reach C 2 octaves above this (on the G string), with a wavelength
of 8 feet.
The relatively long wavelengths mean that
there will be standing waves on the stage, creating pressure minima and maxima,
and resulting in an uneven frequency response at any particular position on the
stage. The position and extent of these peaks and troughs are determined by the
sound's wavelength and the size of the stage (as experienced by the low
frequencies - suspended ceilings for example, tend to be invisible to low
frequencies so they see the concrete slab above (some bass absorption may occur
if there is insulation in the void)).
So the physical reality is complex, and the
extent of unevenness (not necessarily lack) of response is related to
the size of the stage and the nature of the boundaries. My advice to bass
players would be to stand next to the wall if you can, and to position your
amplifier in a corner.
The problem then, of bass players not
hearing themselves on stage, is related to the relatively long
wavelength of the notes they play, but the 32 foot story certainly qualifies as
a tall tale.
If you have any tall tales you'd like to share, or a story you've heard that seems a bit dubious, please write to me or Jill with your myth so we can explore, explain and possibly explode it.