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Air, the medium by which dynamic drivers communicate can be regarded as a liquid, very
difficult to predict and even more difficult to control. When the driver is built into a small
enclosure the complexity of this problem inevitably grows and in fact, of all the
components in the audio chain it is the loudspeaker that produces by far the highest
levels of distortion. Although the potential for improvement is large, the physical
problems that must be addressed are of similar proportions.
A well known audio critic asserts in his opening paragraph that the drive unit is the major
component of modern loudspeaker design. Whilst we would agree it is important it is as
we have clearly demonstrated, no more important than the enclosure.
The moving coil drive unit is a powerful oscillating motor. It reacts with the enclosure in
its effort to convert electrical energy to sound. Undesirable by products created during
this process must be eliminated as much as possible. To date all but very few enclosure
designs have chosen to discount or underestimate the importance of this key concern.
Typically such enclosures can be seen to be composed of flat panels which can be easily
excited. The inevitable predominance of standing waves and high levels of diffraction all
combine to destroy the accurate recreation of sound. The limitation here is the cabinet
makers box. The ability of such designs to perform has always been compromised from
the outset. The larger the box the more the system could be seen to go beyond its severe
limitations.
In contrast the BBC LS3 5a was successful because it recognised these limitations. It
minimised the problem of cabinet distortion by accepting the limitations of the
technology. The generation of low frequency energy poses major problems so by limiting
the low frequency response it confined its task to the bandwidth of its limitations. The
choice of a small, light but very strong box was the outcome of this philosophy, a classic
solution. For Wilson Benesch it was the recognition of these limits and a similar respect
for the physical limitations of materials that informed our approach. This emerged from
our work in turntable design where we had pioneered the use of carbon fibre and
Advanced Composite Technology structures. The limits can be pushed back, but it
requires research and development and the application of leading edge technology and
assembly techniques. The A.C.T. One Loudspeaker enclosure was the conclusion of this
philosophy. Its success has clearly demonstrated just how important the enclosure is.
Within its limitations the A.C.T. One enclosure made high quality, low frequency
reproduction achievable. For other audio engineers as well as audio critics it subsequently
became an invaluable development tool. When we attempted to extend these limitations
by demanding a lower frequency response we went beyond those limits. Overcoming this
significant technological challenge has been the principle focus for our research over the
last three years.
The benchmark that the A.C.T. One loudspeaker set in terms of integration and mid range
transparency prescribed that the low frequency performance should be similar in every
regard. The outcome of this development has major implications for the company which
can now boast a manufacturing facility for advanced moving coil drive units that have
successfully overcome the limitations of the drive units currently used in the A.C.T. One
Loudspeaker.
The Bishop loudspeaker system exploits this new technology to the full.
Conceived, developed and manufactured from raw materials by Wilson Benesch
The Tactic® is an adaptive design. In the mid range system it functions in parallel.
In the low frequency system it takes the form of a composite system the Isobaric
Tactic® The Bishop is a unique product. It incorporates the most advanced
technology but in a simple way, the hallmark of Wilson Benesch design.
The Bishop: General Design Features.
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