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Section 4
Description
4.1 Overview
Professional loudspeaker systems are designed to optimize spectral, spatial, temporal and
usability performance attributes. Quite often optimization in one area compromises
performance in another. Thus, loudspeaker design is the art of balancing these goals while
minimizing compromise. In order to achieve these goals for the KF700 Series, key develop-
ments allowed for performance enhancement in each area without compromise in others.
4.1.1 SPECTRAL
The KF700 Series are true three-way designs. The goal was to develop systems with greater
low frequency extension and greater overall mid frequency bandwidth. Traditionally these
goals required increased physical size. This was not an option. The KF700 Series loudspeak-
ers were designed as uni-axial enclosures in which all the transducers (woofer, mid-range,
and high frequency) share a common acoustic axis. This permitted using larger horns for a
more consistent coverage pattern over a wider frequency range and provided more available
enclosure volume for deeper bass response while actually reducing physical size. A new,
patented mid frequency phase plug was also developed that allows for improved upper
mid frequency response from a cone transducer through a large format horn.
4.1.2 SPATIAL
The KF700 Series have 35° x 35° coverage patterns. This enhances building arrays and
increases overall system output capability. Conventional phase plugs create beam-width
narrowing in the upper portion of the mid-range. The patented KF700 Series mid
frequency phase plug provides upper mid-range extension without creating this narrowing.
The uni-axial approach minimizes the impact of “apparent apex error”. This occurs when
the separation between physically misaligned transducers changes as the listening point
changes. The KF750 horn designs draw heavily from the SimplePhase™ horns used in the
KF900 Series in order to achieve more seamless coverage between arrayed enclosures.
The low frequency section uses multiple woofers in a dipole configuration to reduce off
axis low frequency energy and thus increase directivity. Research showed that the directivity
of the low frequency section could be smoothly matched to that of the mid frequency section.
This is done by optimizing the ratio between the woofer spacing within the mid frequency
horn and the dimensions of the mid frequency horn mouth. This configuration with its
dimensional ratio is patented.
4.1.3 TEMPORAL
The temporal focus is once again on the mid-range section. A mid frequency cone trans-
ducer tends to provide better tonality and lower distortion than standard compression
drivers, but can smear events in the time domain. This was resolved through a redesign of
the mid-range transducer geometry. The multi-axis approach and its subsequent impact
on apparent apex error also serves to minimize temporal inconsistencies from transducer
to transducer within the enclosure.
4.1.4 USABILITY
Usability goals were satisfied by making the enclosures small. The uni-axial approach
met all the performance goals while allowing for a reduction in overall package size. For
the most consistent coverage pattern through the low to mid frequency crossover region,
the optimal spacing of woofers is smaller than the optimal height of the mid frequency
horn. This allows the woofers to reside within the mid frequency horn, once again
resulting in a small overall package size.
In order to provide simple rigging, the standard KF850 flytrack was chosen. The KF750
utilizes these tracks on the front and back of the enclosure, eliminating the need for putting
fingers between cabinets during array assembly or disassembly. Finally, some internal
parts have been molded of lightweight materials in order to meet the desired enclosure
weight of less than 200 pounds.
