LOUDSPEAKERS

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Andrew Jones • Technical Audio Devices (TAD)
Speaker Designer
Roundtable
Being born in stereo (Andrew has an identical twin brother who is left
handed while he is right—making them a stereo pair from birth!) made a
career in audio perhaps pre-destined.
Gaining an interest in electronics and hi-fi in his pre-teens informed his decision
to study Physics at university, followed by six years of research in audio topics
such as computer modeling of crossover networks and active noise cancellation.
In 1983 he was invited to join KEF Electronics as a research engineer, progressing
to become Chief Engineer. After eleven years at KEF he moved to the USA to join
Infinity.
In 1997 he was invited to join Pioneer to lead the engineering group in designing
speakers. This culminated in the formation, 10 years ago, of the consumer division
of TAD, and the exploration of designs without compromise.
His spare time (what spare time) is split between travel, tending to his dogs and
cats (yes, plural, very), and archery (he recently qualified as a coach and is to be
found teaching each weekend when he is home at the local archery range).
What are the particular challenges and trade-offs of designing a
small loudspeaker Which sonic qualities are you primarily trying to
optimize, and which qualities are you most willing (or compelled) to
give up
Small speakers typically lack the sense of scale and dynamics of large
ones, the qualities that give you that sense of reality, effortlessness, and
ease. In contrast they can disappear in a way that is difficult to achieve
from large speakers. The challenge is in retaining both. Typically smaller
speakers are used in smaller rooms, so the designer can take advantage of
this to some degree and use the room gain to offset the loss of dynamics
in the midbass region. Also smaller speakers are normally equated with
lower-cost speakers and that brings its own set of compromises that are
independent of size. When cost is divorced from size then the performance
loss from small speakers can be made very small indeed, and be confined
only to very low, very loud bass.
Do you have your own design techniques that
maximize the performance of small designs
Generally, the first thing to go from small speakers
is bass. In order to maximize bass extension, one
must necessarily give up efficiency. This means
that to get any degree of real-scale dynamics you
must put in a lot of power. The speaker not only has
to handle this power without damage, it must do
so without dynamic compression. Compression in
the mids and highs can be dealt with by designing
the drivers to have high inherent efficiency, but for
the bass driver this is not an option. Piling on more
magnet, or using a lighter cone, only gives less low
bass. For any size of cabinet and required bass
extension there is an optimum set of parameters of
mass and magnet strength that will give the correct
bass alignment, so the only solution is to design
30 Guide to High-Performance Loudspeakers www.theabsolutesound.com
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