| 摘要 |
<p>PURPOSE:To improve the efficiency of reproduction at a frequency lower than f0 neither by spoiling the efficiency at a frequency higher than minimum resonance frequency f0 nor by increasing capacity, by increasing mechanical resistance of vibration by decreasing the voice coil impedance of a speaker and by connecting a low-pass filter to the speaker. CONSTITUTION:In the range of frequencies higher than minimum resonance frequency f0 of speaker 1, the lowest voice coil impedance is set to 4OMEGA, and consequently while its sound-pressure/frequency characteristics are shown by (b), the impedance frequency characteristics are shown by (b'). Then, low-pass filter 2 which increases the impedance at frequency (e) of the impedance frequency characteristics (b') is connected in series to speaker 1, the vibration part of which is applied with a damping coating material to increase the mechanical resistance of vibration, so that the said characteristics will be varied as shown by curves (d) and (d') in the figure.</p> |
