With the objectives of the project being satisfactorily met, the Enhanced Ion Tweeter is an immense success. This feeling is intensified by considering that none of the personnel, advisors, or other contacts was even sure that such a project was even
attainable in the realm of modern solid-state electronics.
Enhancements. The Enhanced Ion Tweeter has increased the power
efficiency over the older vacuum tube-based designs, resulting in a 40% savings in power consumption for the same output. The per-unit cost of the Enhanced Ion Tweeter is around 45% less
costly than the comparable vacuum tube-based design. Furthermore, this ion tweeter has a self-starting flame, a significant advancement over nearly all of the other tweeters that required manual starting of the flame. The high voltage system (excluding
the coil) is also significantly smaller.
Shortcomings. The sound quality of this device is not as good
as the vacuum tube-based device, nor is the sound output level high enough
for all applications. Fortunately, we believe that both of these shortcomings can be corrected by using more
advanced design techniques and more sophisticated measurement equipment.
Recommendations. With the enhancements and shortcomings being
mentioned, we now turn our attention to listing recommendations which we
believe would further bolster the marketability of the project.
- To increase the linearity of the system, we believe that PWM would
be nearly ideal. The PWM would feed the gate driver, which has extremely high input impedance, so virtually no extra power is required. Because of this, the devices would likely be
very small and take up almost no space. Both of the foregoing would be beneficial, because the power amplifier draws up to ~25 watts of power and requires heat sinking to modulate the power rail. It requires very high precision circuitry to operate at
around 5MHz, however.
- Another possible method would be Faraday shield modulation,
whereby the voltage on the Faraday shield is changed with the audio signal. We found that it required voltages in the vicinity of 10kv to produce audible sound. A television flyback
transformer, which has both the necessary voltage output, as well as the necessary bandwidth (around 20kHz).
- Audible hiss was present at 3.6MHz, and 7.4MHz was too difficult
to do with the technologies we had access to, so we settled on 5MHz as a compromise. The flame still flickers at 5MHz, but is virtually noise-free. Above around 15MHz, the flame begins
to change from blue to yellow-white and looks more like a flame produced by a candle. This type of flame is perfectly still and noise-free. Increasing the coil resonant frequency seems to have a positive effect on the flame, but it requires clever or
more complicated applications of the technology.
- The ultimate goal of increasing the power efficiency it to produce
a larger electric flame with less waste heat. The larger flame is desirable because the audio bandwidth of the flame is directly related to the size of the flame. A larger flame can
produce lower audible frequencies in the human hearing range. The upper limit of the ion tweeter’s response is of no concern since it is far above the human hearing range.
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