| 摘要 |
<p>PURPOSE:To expand a low-pitched sound reproducing area, by connecting a negative resistance circuit in series to a loudspeaker, making the circuit concerned have negative resistance at less than prescribed frequency, and also adding an impedance circuit. CONSTITUTION:A negative resistance circuit 3 has negative resistance at less than the lowest resonance frequency. That is to say, it is constituted of a voltage inverted type transistor circuit, and to this circuit, a low-pass filter 4 having cut-off frequency fc is connected. This circuit 3 has negative resistace in an area which is less than the frequency fc as shown in the figure, therefore, Dc resistance Re of a moving coil becomes as a dotted line shown in the same figure, and in an area being less than the lowest resonance frequency fo, acoustic pressure drops by 6dB/oct, and also in an area exceeding the frequency fo, the negative resistance circuit 3 has no negative resistance, therefore, a peak in an acoustic pressure characteristic is not generated in a series resonance point omega1 of electric inductance Le of the moving coil, and momentum impedance Zm.</p> |
