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The Bishop was developed with two discrete isolated enclosures for the low
frequency, mid range and high frequency systems. This immediately reduces
corruption from cross communication. A two box system also provides other
advantages in terms of manufacturing and installation. Curved pre stressed
Advanced Composite Technology panels are key structural components in both
cabinets. An organic moulded carbon component has been developed to facilitate
low defraction and negligible resonance from this critical part of the structure. The
form and angle of rake eliminates the potential for ceiling to box top interactions.
The whole system is mounted on a substantial foot system which also houses the
adjustable crossover system whilst providing a high degree of stability. All
components are manufactured in house with the exception of the tweeter which is
specified to Wilson Benesch specifications and mounted in a simple but very
effective damping ring on the alloy MDF composite baffle structure. It provides
clearly defined information from 5kHz to 20 kHz via a single inductor capacitor 1
st
order crossover network. Its position has been derived from trials which focused
upon phase coherence. The Mid range units are driven well within their prescribed
specification and are controlled by a bandpass filter. All low frequency information
being devoted exclusively to the Isobaric Tactic® system. Significantly low
frequency energy is provided by drivers that are almost identical to the mid range
systems. This dictates that integration and phase coherence will be virtually
guaranteed. To further overcome the enormous challenge of low frequency
reproduction these units have been mounted in a clamshell composite configuration
which we call the Isobaric Tactic®. By exploiting the principles of the Isobaric
loading the volume required by the low frequency driver array, ( eight in each
channel ) has been minimised despite this advantage it is still five times greater than
that of the A.C.T. One Loudspeaker low frequency enclosure. This has been
achieved by extending both height and depth but not width. This important detail
maintains the slim forward facing profile which is crucial for imaging and
transparency. Moreover, the exterior has been extended without accepting the
unacceptable compromise of the flat surface. Low frequency production is extended
down to 30Hz without the use of the ported enclosure loading which is
compromised from the outset due to the highly resonant characteristics of the port
output which is of course is always 180 degrees out of phase. This delay is
eliminated in the infinite baffle arrangement. The speed of the attack and decay are
the main benefactors as a result of this approach.
The Tactic® Dynamic Driver.
Early in 1996 a 12 month feasibility study concluded that currently available driver
technology would not be capable of taking the companies ambitions forward. The
study indicated further, that significant potential for development existed but that it
would be a major under taking. The decision was taken for us in many ways, the
moment we realised how innovative the final product would be. At that time our
attentions were focused on the creation of low frequency information and in
particular the ability of that system to integrate well with the improved mid range
performance. A variety of diaphragm sizes were assessed including race track types.
Orientation was also studied, side firing notably being the most un-popular. Loading
the system with transmission lines was appraised as was the closed box. Many hours
of research was devoted to the
search for a solution to the problem. The breakthrough was made when the Isobaric
method was explored. Using B stock Scan drivers in a hastily assembled MDF box,
for the first time, it was instantly recognised as the right solution. An obvious
answer in
retrospect for with drivers of similar physical proportions to the mid range system
matching would be axiomatic. For the first time we could hear highly integrated,
high performance reproduction that was un-questionably superior to the A.C.T.
One.
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