(i) Explain the working principle of Electrostatic and permanent magnet speaker. (ii) Compare Woofer and Tweeter.
1 Answer
Answer :
(i) Electrostatic speaker.
The voltage is applied to the central or movable plate, the signal voltage is applied to the two outside plates causes these plates to attract or repel each other. The amount of attraction or repulsion depends on the applied voltage. If one of the plates is flexible metal, it will bend. But the amount of attraction and repulsion is not directly proportional to the applied voltage.
A light voice coil is mounted so that it can move freely inside the magnetic field of a strong permanent magnet. The speaker cone is attached to the voice coil and attached with a flexible mounting to the outer ring of the speaker support. Because there is a definite "home" or equilibrium position for the speaker cone and there is elasticity of the mounting structure, there is inevitably a free cone resonant frequency like that of a mass on a spring. The frequency can be determined by adjusting the mass and stiffness of the cone and voice coil, and it can be damped and broadened by the nature of the construction, but that natural mechanical frequency of vibration is always there and enhances the frequencies in the frequency range near resonance. Part of the role of a good enclosure is to minimize the impact of this resonant frequency.
(ii) Compare Woofer and Tweeter.