1. In order to obtain the diaphragm with basically unchanged charge distribution, a scheme of designing the diaphragm with semiconductor materials is proposed. Because semiconductor materials have the characteristics of significant changes (such as temperature and light) under the influence of external conditions, it is obviously not feasible to use them to make vibration membranes. The design scheme of diaphragm is: volume resistivity 106~108 ω· Cm synthetic diaphragm, high strength and flexible material.
2. The polarization power supply is omitted, and the diaphragm is made of electret material. It is considered that the electret is a polarized or charged diaphragm and does not require a separate polarization voltage. But the experiment shows that it is not suitable to use electret material to make diaphragm. Another consideration is the use of polarized power supplies in audio signals. This is based on the consideration that although the polarized diaphragm requires very high voltage, the required current is very small (≤ 10 μ A), and the power consumption is extremely low. The disadvantages of this scheme are: the distortion is inevitably increased; Secondly, the structure tends to be complex.
3. Mistakenly thinking that horn speakers are easy to absorb dust. This is due to the fact that there are many electrostatic environments around us, which are easy to collect dust. In fact, the condition of electrostatic precipitation is that the electrostatic charge must ionize the dust particles to adsorb them. But the horn loudspeaker works under the condition of alternating electric field. When the electric field strength exceeds a certain critical value, it is possible to ionize dust and collect dust. Under normal working conditions, the electric field strength is less than the above critical value. Therefore, dust prevention is too much considered in design.
4. The horn type loudspeaker is not suitable for high sound pressure. Such problems do exist in early electrostatic loudspeakers. The reason is that the diaphragm of early horn loudspeakers is mostly made of metal, with low tensile strength, which is easy to crack and damage under high sound pressure. In addition, the fixed electrode insulation of early horn type loudspeaker is poor. When the sound is played at high sound pressure, the movable electrode has large amplitude, and the insulating medium between the two electrodes is broken down by high voltage, resulting in corona. With the progress of the material industry, the use of polymer high-strength diaphragm materials in horn loudspeakers has been quite common. In addition, it is no problem to obtain insulating electrode plate materials with withstand voltage greater than 6KV. The measured results show that the horn loudspeaker with a vibration area of 10000mm2 can stably output 110dB sound pressure for a long time.
