David Moulton

Elliptically shaped transducer enclosure

An enclosure for transducers incorporates an interior acoustically reflective shell. This acoustically reflective shell is shaped so that the inner surface thereof is the envelope of at least a section of a cylinder of elliptical cross section, an ellipsoid of revolution, or the envelope of a multitude of said shapes oriented so that the elliptical shapes share one common focus and each has one distinct focus. In this last case, transducers are placed at the distinct foci so that sound produced by them is directed substantially toward that portion of the elliptical acoustically reflective shell to which the distinct foci belong. In operation sound generated by the transducers, operating in phase with one another, is focused and concentrated at the common focus such that this common focus acts as a singular source of phase coherent sound of any desired angular beamwidth and intensity. If the acoustically reflective shell consists of a section of a single elliptical shape, a transducer is placed at one focus oriented so that either front or rear generated sound is directed substantially toward the elliptical shape, reflected and focused at the other focal point. Sound emanating from this second focal point may be phase coherent, and have angular beamwidth and intensity as desired.

A new loudspeaker design: A case study of an effort to more fully integrate the loudspeaker into the playback room in a musical way

The authors have been members of a design and development team that has created a new loudspeaker that attempts to resolve several of the primary problems presented by the loudspeaker/room/listener interface, as described in one of the author’s previous papers. This paper will describe that new loudspeaker, its various new approaches to the interactions between the loudspeaker, the room and the listeners, and a brief review of the research, findings and assumptions underlying its design. The authors hope to have examples of the loudspeaker available for demonstration.

Power chords, polyphonic trains, and plain old phase

Power chords, polyphonic trains, and plain old phase is a 36-min work of music composed directly for a six-channel array of loudspeakers (reduced to 5 channels for this performance). This piece draws on the work of minimalist sculptors such as Donald Judd and Michael Heizer, and explores the evolving nature of slowly shifting phase, reverberation, and the sonic continuum, using extremely simple sonic materials.

Issues pertaining to the composing of ``minimalist'' loudspeaker music for home theater arrays

Loudspeaker music composed for home theater loudspeaker arrays is subject to a different set of aesthetic principles and production problems than is music (live or otherwise) prepared for concert presentation. Issues of scale, timing, dynamic range, spectral range, sonic materials, reverberance, the treatment of spatial issues, and listener expectations will all be discussed.

Design considerations for an idealized domestic surround-sound listening space

I have been actively involved in the production of music for surround-sound systems since the late 1960s, including composition, production, recording (classical, multichannel pop, and experimental), loudspeaker design, and acoustical design. Based on my experiences, I am going to present some design principles (and constraints) for domestic (and public) surround-sound playback spaces, possible loudspeaker configurations, and topologies. I will also suggest a possible ideal domestic music playback space.

Loudspeaker array as a musical composition genre

A fixed array of loudspeakers can be used as a proprietary format for electronic music composition, leading to a fixed genre of work. The author will describe his experiences using a 6‐channel array of full‐range loudspeakers, describing the compositional principles he has employed, including issues of source localization, ambient and reverberant fields, available bandwidth, and sound‐pressure levels. Spatial relationships, musical issues and problems, and related concerns will all be discussed.

The loudspeaker as musical instrument: an examination of the issues surrounding loudspeaker performance of music in typical rooms

The loudspeaker is the most important and one of the most variable elements in the electroacoustic music performance process. Nonetheless, its performance is subject to a ‘‘willing suspension of disbelief’’ by listeners and its behavior and variability are usually not accounted for in assessments of the quality of music reproduction or music instrument synthesis, especially as they occur in small rooms. This paper will examine the aesthetic assumptions underlying loudspeaker usage, the general timbral qualities and sonic characteristics of loudspeakers and some of the issues and problems inherent in loudspeakers interactions with small rooms and listeners.