Electronic Design

Piezoelectric Dome Delivers Better Speaker Sound

Murata Electronics has designed what it claims is the world’s first super tweeter drivers that are able to improve the total sound of a speaker and not just reproduce high frequencies, as with conventional super tweeters. Murata’s proprietary design does away with the ordinary magnetic-based drive system and instead uses an active piezoelectric dome with an integrated drive system. Murata’s super tweeters improve a finished speaker’s overall perceived transient response (even for bass frequencies), expands and opens the sound stage, and enables excellent listening from a wide range of off-axis locations.

To achieve these benefits, Murata starts with a proprietary piezoelectric hemispherical ceramic dome employing a “breathing mode” vibration system that allows the entire surface of the dome to react acoustically. As the entire surface of the dome expands and contracts—like a balloon—sound radiates in all directions, eliminating the narrow beaming effect typically associated with high-frequency drivers. This ultra wide sound dispersion at higher frequencies creates a wider sound stage image and increases the ability to locate individual sound sources across the sound stage.

Most dynamic drivers, regardless of frequency, struggle with transient response and the resulting muddiness of sound to some degree. Dynamic drivers operate above their resonant frequency, which is not ideal for the best transient response. Murata’s super tweeter drive system is capacitance based and operates below its resonant frequency, which allows it to have much better transient response. While Murata’s super tweeter is not able to directly reproduce low bass or midrange frequencies, it is able to reproduce the higher-order harmonics of these lower frequencies. The improvement in the transient response of these higher harmonics results in a better-defined base and midrange response of the overall speaker.

It’s not difficult to implement the Murata super tweeter in new or existing designs. Another benefit of a capacitive-based drive system is that it acts as its own filter, naturally suppressing the lower frequencies it is unable to produce. Thus, no crossover is needed allowing for quick prototyping or critical evaluation of the super tweeter driver in existing systems.

The horn loaded ESTD01 has a frequency range of 15 kHz to 100 kHz, and an average sound pressure level of 90 dB/W/m. The non-horn loaded ESTD02’s frequency range is 30 kHz to 100 khz with a 90-dB/W/m average sound pressure level. While both drivers can operate below 15 kHz, the drivers are not intended to replace a tweeter due to the roll off in the super tweeter’s response.

The breathing mode drivers are available for $199 (ESTD02) and $299 (ESTD01) each. Lead time is approximately 12 to 14 weeks. The company will provide samples to qualified speaker manufacturers.

Murata Electronics
www.murata.com/catalog/p57e.pdf

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