About Marshall Choong
Modern loudspeaker design concerns finding the best compromise
of a complex mixture of technologies, limited ultimately by the physics of
acoustics and finally assessed by the often little understood, but amazing,
properties of our hearing.
We strive to justify by any and all decisions made during the
design process by measurement or simulation. However many areas such as image quality, listener envelopment
and other room related issues are still difficult to quantify and relate back
to speaker design. After a number of years of experimentation with our own
recordings, it became clear that for the audiophile, the
Ambisonics
system pioneered by Michael Gerzon in the 1970's was by far the most accurate
and flexible recording format. From the perspective of loudspeaker designers it
was hoped that this would provide us with pristine unprocessed material for
listening tests.
Finally in 2019, this aim was achieved and experiments continued with
multichannel playback. Presenting this music to interested listeners easily
showed a strong listener preference for Ambisonic multichannel playback and also stereo playback
from the same source.
After a number of years an examination of the detailed performance of
drivers, in terms of complex intermodulation products, has enabled us to
correlate the result with listening performance to a surprisingly high degree.
The performance of loudspeakers in typical room environments is also an area of
special interest to us. All techniques to improve the difficulties of the
reproduction of bass frequencies in rooms have been investigated. The final
outcome is in agreement with the perceived wisdom of the audiophile community.
In systems of the highest quality, almost all 'solutions' for room modes fail,
are not practicable, or are far too expensive. Loudspeakers are invariably in
the wrong room position for the minimum excitation of room modes, and if they
have extended bass, this leads to inaccurate and unacceptable bass level
response and poor bass dynamics.
This phenomenon has been understood by loudspeaker
manufacturers for decades but has been largely ignored in the commercial
markets.
Where state of the art bass is required, our approach to this problem is
twofold:
1. The main speakers do not have to have a fully extended bass
response.
(The bass response of a typical 2 or 3 way closed box
design is preferred by many.)
2. Bass can be extended by the use of multiple subwoofer
products, specially designed for this application. This technique has produced the most accurate
bass that we have measured or heard but is impractical in most domestic environments.
The final outcome to this research is to make available loudspeakers with well behaved
phase shifts, with unusually low rate of change of phase i.e. low group delay, which
all points to closed box loudspeakers or dipoles.
Phil Marshall is responsible for all electronic and loudspeaker design, except aspects of industrial design,
and worked in the audio industry since 1970 starting as an engineer with Dolby
Laboratories when they were based in Clapham, South London. After 15 years, this was followed,
initially, as a consultant amplifier designer with NAD until they left the UK in the 1990's.
John Choong is a consultant industrial designer also with a lifelong interest in music reproduction.
John also worked for NAD being responsible for re-designing their product ranges in the 1990's.
He also worked for Tag McLaren during their high tech venture into audio products.