A Novel Approach to Linear Phase Loudspeakers Using Passive Crossover Networks
Assuming equal electroacoustic transducer efficiencies in a multiway loudspeaker system, the vector sum of the voltages to the individual drivers must be equal to the input voltage for the accurate transfer of amplitude and phase characteristics of the signal. It has been shown that this is achievable using 6-dB per octave passive filters or higher slope active filters at a low signal stage to avoid unacceptable loss of power. Passive filters of 6-dB per octave slope require transducers with a power bandwidth not achieveable with today's technology, while active filters requiring multiple amplifier systems are still too expensive to be provided commercially, especially in multichannel sound systems. Passive filters are described using one or more auxiliary loudspeakers, -the missing link,- in 12-dB per octave and higher degree crossover networks, which at the same time fulfill the requirement that the vector sum of the part voltages be equal to the input, theoretically without loss of power in the crossover network. Linearity of phase and amplitude are thus assured i the electrical circuit. Other requirements for linear phase loudspeakers are also described. Comparisons between computer calculated transfer functions and results from a practical high-performance low-distortion loudspeaker are shown.
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