As a sound output device, the microphone plays a very important role in the entire sound reinforcement system. A perfect set of wireless microphones will bring great convenience to people's use, and at the same time provide the sound engineer with a space for artistic creation on site. Therefore, when constructing an audio system, more or less wireless microphones are configured.
There are many ways to call wireless microphones: wireless microphones, wireless microphones, wireless handhelds, wireless headsets, wireless chest microphones, wireless microphone systems, etc., which generally do not cause misunderstandings.
The history of wireless microphones is not long, only one or two decades, but it has developed extremely rapidly. We rarely saw it in the 1980s. The products are nothing more than a few international microphone manufacturers such as Siya; in terms of application, they are only seen in large-scale concerts abroad. Over time, brands like Audio-Technica, Sennheiser, Sony, and EV have gradually entered the domestic high-end audio system.
With the development of electronic technology and the increasing application, the technology, market, and application of wireless microphones have made great progress, and the prices have gradually become approachable. Various brands and types of wireless microphones are emerging in endlessly. Especially in the past few years, domestic wireless microphones have sprung up, occupying half of the mid- and low-end markets. In Enping, Guangdong, there is even a distribution center for the production of wireless microphones (microphones).
Relatively speaking, wireless microphones are more expensive than wired microphones, are technically more complicated, and are more delicate in use. Therefore, this article introduces how to choose and use wireless microphones.
1. Technical development of wireless microphones
The wireless microphone has gone through about three stages from a simple wireless FM transmitter and wireless FM receiver to the current use of dedicated PLL (frequency phase-locked loop) technology.
1. Simple FM transmitting and receiving
At that time, in order to get rid of the fetters of the microphone cable, people thought of the principle of transmission and reception similar to FM broadcasting, through the microphone's transduction principle and the audio→modulation→amplification→transmission process, and then through the FM radio or special receiver (special frequency point ) Receiving and playback. It is conceivable that its sound quality, stability, anti-interference ability, etc. cannot meet the needs of actual use.
2. How to choose and use wireless microphone for FM transmitter and receiver of quartz oscillation
Due to the RC or LC oscillation generated by the electronic circuit, the stability of its oscillation frequency is greatly affected by the environment, and its frequency cannot be very high. Generally, it can only be below 200 or 300 MHz. In this frequency band, It is very susceptible to interference from other signals. At this time, a transmitting and receiving circuit using a quartz oscillator appears. As everyone knows, the oscillation frequency of quartz crystal is very stable. The wireless microphone transmitter and receiver composed of it work much more stable. At the same time, its working frequency can be in the V segment (30MHZ-250MHZ), U segment (200MHZ). -1000MHZ), the external interference signal is not serious, which brings better results to the use of wireless microphones.
In use, because the oscillation frequency of the quartz crystal is not adjustable, for a set of wireless microphones, the receiving and transmitting frequencies are fixed and require one-to-one correspondence, which is not very convenient. If there is interference on the point, the wireless microphone cannot be used.
3. Wireless microphone with PLL reception
PLL is the abbreviation of frequency phase locked loop in English. In the transmission and reception of wireless microphones, frequency synthesis is adopted, which can receive signals satisfactorily in a frequency band. In this frequency band, the working channel can also be switched arbitrarily. Theoretically, in a 24MHZ frequency band, if you use 1MHZ as the channel resolution, you can switch 25 channels; if you use 125KHZ, you can switch 193 channels. As for the number of channels, the receiver's bandwidth and channel resolution Degree related.
In actual use, it is necessary to take into account many factors, but it is certain that the receiving channel of the wireless microphone using PLL technology is adjustable, and there is more than one, which brings great flexibility in use. The transmitter and receiver can also be combined at will, and only within a frequency range, the working channel can be switched at any time to avoid interference.
The first type of wireless microphone on the market has been eliminated and is only used in general experiments. The second type also only exists in low-end products or in old products, and wireless microphones using PLL technology are widely used.
4. Diversity reception
Since wireless microphones use frequency modulation technology, their working frequency bands are in the V or U section, and the electric waves propagate in a straight line. When they encounter obstacles, they can only reflect, not diffract. As a result, shadows or blind spots will be generated, which will affect the use of the microphone (light sound, FM noise, etc.). In order to avoid this situation, the current higher-end wireless microphones use diversity receiving technology. The so-called diversity receiving is A system needs to have the same two receiving devices. The signal from a transmitter is simultaneously amplified by two FM receivers after frequency discrimination and low frequency, and then added to the combiner. The combiner is actually a selector. Choose a stronger receiving signal as the output signal at every instant, which can effectively improve the receiving effect.
Understand the technology of the above-mentioned wireless microphone, we can choose a suitable wireless microphone according to our financial resources.
In general use cases, such as not far away (within 20 or 30 meters), used in meeting rooms, multi-function halls, etc., when the moving range is not large, you can choose a quartz oscillator type, single-receiving wireless microphone , Microphones can choose dynamic, electret and other types, conditions permit, and PLL-type wireless microphones can also be selected.
In performing arts bars, theaters and other occasions, due to the large moving range, complex receiving conditions and high requirements, it is recommended to use PLL type and diversity receiving.