Direct Acoustic Digital-to-Analog Conversion with Digital Transducer Array Loudspeakers
[Engineering Report] Different direct-converting, digitally driven loudspeaker array prototypes have been developed with moving-coil transducers. An evaluation of the radiated sound-field quality in terms of distortion figures over the three-dimensional space in relation to the main driving transducer properties is presented. The effect of key experimental factors such as transducer mismatches, array size, transducer interspacing, baffle diffraction, and transducer arrangement on the radiated sound-field properties was isolated and quantified experimentally. Values of total harmonic distortion (THD) in excess of those set by quantization distortion were found at listening distances typical of a normal-size room for prototypes made with tweeters. A smooth rolloff in the transducer frequency response resulted in improved THD figures, and a wider transducer bandwidth resulted in increased reconstruction bandwidth. Future research directions are established for the multibit direct acoustic digital-to-analog conversion, and performance bounds are set on the characteristics of transducers needed for digital reconstruction.
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