A polymer that listens and talks!
A polymer made of 1,1-difluorethene, polyvinyleden difluoride (PVDF)
is what you call piezoelectric. In other words, - it will produce an
electrical current when bend or pressed. You can make a long
ribbon or bend it in almost any shape. It will then act as a microphone
or a speaker.
Disadvantages: The polymer film is quite expensive - approx 12 US
dollar for a small 4" by 4" square. Soldering lead wires to
the film is very difficult as the surface "moves" on the
microscopic level. Soldering with very high silver contence has been
usede with great succes. The frequency range is limited to the upper
range - depending on the size the lower limit is typicalle around 3-5
kHz. |
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| AUDAX
http://www.audax.com/tech/tweeter_edome.shtml
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The HD-3P tweeter represents the first in a new generation of loudspeakers.
This tweeter features a piezoelectric
polymer film, coated on both sides with a vacuum deposit of pure gold,
for the diaphragm. This polarized film is clamped to an elliptical ring with a sealed
and pressurized chamber behind it. A dome is formed by the constant, positive
force from the pressurized gas on the film.
The transducer uses no voice coil or magnet to produce sound. As an
electrical signal is fed to the metal electrodes deposited on both sides of the
ceramic film, the surface area of the diaphragm responds by elongating and
contracting proportionally in size with the signal. Sound waves are generated by the
stretching of the diaphragm, which is
converting the vibration into a pulsating motion, rather than a piston motion. The
transient ability is unmatchable with
dynamic drivers because the moving mass of the HD-3P is approximately
twenty times less than a conventional 20mm dome tweeter, while the directivity
is equivalent. The HD-3P is supplied with its own crossover network. The crossover
frequency can be customized by adjustment of the component values.
The HD-3P was developed for use in 2 and 3 way systems, with a -6 dB/octave
crossover at or above 6 kHz. System sensitivity should be inthe range of 86 dB to 94 dB. The impedance
of the HD-3P is 4 Ohms.
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| GALLO
http://www.roundsound.com/
Duo is the latest speaker from Anthony Gallo featuring the patented CDT™
tweeter, placed between two 4" Mid- woofers. Gallo claims "the most natural and extended trebles of any speaker on the
market". Sensitivity is stated to be 93dB and bandwith going to
40kHz along with textbook- perfect dispersion. |
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CDT...
Anthony Gallo calls his tweeter "A tweeter without compromise". His proprietary design is called CDT, or
Cylindrical Diaphragm Transducer. Gallo spent eight years refining this
creation. As the Gallo marketing literature points out: "The CDT uses no voice coil or magnets. Instead, the signal is passed across the conductive
surface of the diaphragm, which attempts to expand, while the cylindrical shape of the
driver supplies the necessary restorative force." The diaphragm is made from an
aerospace plastic called Kynar®, coated in silver. Only high purity oxygen-free copper
is used for the wire leads, soldered to each end with silver. The tweeter is surrounded
by a custom made aluminum enclosure - it is most effective in providing protection. The Gallo literature also boasts that the tweeter is impervious
to electrical or mechanical damage. |
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