Source Model Loudspeakers
David Wessel
adapted by Adrian Freed from Computer Music Journal, Vol. 15, No.4,
Winter 1991
Instead of placing a number of loudspeakers in separate locations to achieve
stereophony, surround sound, or simulations of room information, I propose
the development of a loudspeaker system that is concentrated in a small
and single location and that has a programmable radiation pattern. It would
be the computer instrumentalist's sound source.
One motivation for this idea comes from a number of frustrating experiences
with chamber music that mixes electroacoustic and traditional acoustical
instrumental sources. Here the acoustical instruments are unamplified but
the electronic part is passed through a stereo or quad system. The usual
result is that the electronic part and the acoustical instruments sound
as if they are operating in entirely different acoustical spaces.
The system I am proposing would be an amalgam of digital signal processing
and loudspeaker technologies. The system would allow for time-variant control
of the polar radiation pattern as function of frequency. It should be capable
of simulating the radiation characteristics of acoustic instruments that
vary in dramatic ways with the musical materials.
A look at the literature on acoustic instrument radiation (for a summary
see [Fletcher and Rossing 1991] ) shows that the polar radiation patterns
vary considerably as a function of frequency. Furthermore, the nature of
this variability is different across the various instruments. This is true
not only for musical instruments but also for other natural sound sources.
One is also struck by the fact that conventional loudspeaker radiation patterns
are much more homogeneous than those of the acoustic sources. Indeed, much
effort has gone into the design of speakers so that they behave in this
more neutral manner. Furthermore, conventional loudspeakers, when viewed
across the spectrum, are much more directional than the majority of natural
sound sources.
I am not proposing this type of speaker system as a replacement for the
stereo or surround-the listener approach. I view it as a compliment to these
approaches with some special advantages. Such systems would allow the computer
musician to perform in an acoustically compatible manner with traditional
instrumentalists. If manufactured with portability in mind, performers could
take fuller responsibility for their sound, facilitating that more personalized
sound that I have argued for earlier. The synthesist could specify the time
variant radiation pattern behaviors in a way that is tightly coupled with
the synthesis algorithm. Finally, there is a social implication. If such
systems prove satisfactory, they would help calm the religious wars between
"acoustic" and "electronic" performers and stimulate
the development and performance of an intimate and mixed music that would
thrive in small private and public spaces.
References
Fletcher, N.H., and T. D. Rossing. 1991. The Physics of Musical Instruments.
New York: Springer-Verlag.