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Acoustic Lever
Thiele-Small measurements
Polar
response measurements
Class-D
amplifier
Compression driver phase plugs
Low
thermal compression voice coil
Improved phase plug design
Improved phase plug sound quality
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The Acoustic Lever is a new loudspeaker
enclosure technology which substantially improves the efficiency of the
system. It is completely described in Earl Geddes article in the
January 99 issue of the Journal Of the Audio Engineering Society.
The patent has issued.
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Patent #6,269,318, discloses technology
which allows for a much better method of measuring the T-S
parameters of a loudspeaker than currently available techniques.
Using simple current, voltage and SPL measurements and some computer
calculations the T-S parameters can be measured in-situ without the need
to "perturb" the system. The perturbation methods do not
allow for high accuracy. Licenses for this technology are
available for any application area.
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Current state of the art in loudspeaker
polar response specification requires a very large number of frequency
response curves to be stored in a file. This file can easily
become huge (more than a Gigabyte) for even reasonable accuracy.
This patent shows how this data can be reduced using transform theory to
a set of parameters which has infinite resolution and acceptable
accuracy with a data reduction on the order of one thousand times or
more. This patent was abandoned because of too limited
coverage to make it useful.
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Current state of the art in class D
amplifiers yields far too much EMI to be acceptable in many
applications. This patent discloses how to use a random comparator
signal that lowers both the EMI and the
distortion, Further improvements in sound quality are also shown.
This patent was abandoned because of similar work done by TI. This
technique IS NOT covered by the TI patent however. |
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The phase plug must be designed to
match the waveguide if directivity control is desired over the widest
possible bandwidth. The optimum phase plug design is different for
every waveguide and only an axi-symmetric polar pattern wants an axi-symmetric
phase plug. The
optimum design phase plug for an elliptical polar pattern would be
elliptical - the same is true for other patterns as well. This
patent has issued. |
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Copper and aluminum voice coils both
suffer from extreme variations in their resistivity with temperature
causing sever thermal compression of the output. Using an alloy of
copper with a few percent Nickel reduces the sensitivity of resistance to
temperature by ten times or more. Motor structure modifications are
usually required. This patent was abandoned when the examiner
claimed that it was prior art - I disagree. But that means that this
technology is in the public domain. Contact me for more information. |
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The current genre of phase
plugs for compression drivers are mostly based on the work of Bob Smith.
Bob Smith's approach intended to minimize the propagation of standing
waves in the chamber just in front of the diaphragm, but it does not
optimize the flatness of the wavefront emitted from the phase plug.
Flat wavefronts are critical for waveguide designs that do not rely on
diffraction for wavefront control. This patent describes a design
technique which optimizes the wavefront flatness for better directivity
control. |
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Turbulence in a phase plug is
a major source of poor sound quality, particularly at high levels (since
turbulence rises with the square of the particle velocity.) A simple
design change can significantly reduce this turbulence thereby reducing
the incoherence in the sound wave caused by the random influence of
turbulence. This patent was abandoned when it was discovered that
compression drivers had no audible nonlinear distortion. So why fix
it? |
