Over the years a whole array of wireless audio transmitters have emerged which are supposed to eliminate the cables at home when connecting audio equipment. We will examine the impact of new technologies on the performance of these products. Also, we'll examine if they keep their promise of eliminating the cable clutter.
AM and FM radio was introduced several decades ago and was the first type of wireless audio transmission. FM radio is still popular until today although some newer technologies such as satellite radio and digital radio formats such as HD radio and DAB radio have begun to replace traditional FM radio. Today a multitude of consumer devices exist such as wireless microphones, wireless surround sound kits, Bluetooth audio transmitters, baby monitors etc which eliminate the cord by transmitting audio wireless.
Many homes which are not wired for audio and are ideal for using wireless audio to distribute music throughout the home. We will look at the advantages and disadvantages of today's wireless audio technologies.
One of the most traditional technologies is FM broadcasting. Audio is sent via a radio-frequency signal which is modulated (changed in frequency) with an audio signal. This method is called frequency modulation or FM for short. The biggest advantage of FM transmitters is their simplicity and thus cost and range. As a result, most of today’s 900 MHz wireless headphones use FM transmission. However, FM has some major drawbacks.
The FM signal will pick up static. Therefore there will be noticeable background noise. The amount of static will depend on the location of the transmitter and radio. The reason for the varying quality is a phenomenon called multipath fading which is a result of reflected radio waves cancelling each other out. Using two antennae is one method some devices cope with this problem (diversity receivers). FM radios will easily pick up interference from other consumer devices which is another problem.
Another technology which has gained popularity recently is called Bluetooth. Bluetooth was originally designed to connect computer peripheral devices wirelessly. Bluetooth audio transmitters will convert the audio signal to digital information and then transmit via the Bluetooth protocol. One of the advantages is the high robustness against wireless interference. However, Bluetooth was not designed for audio transmissions. Therefore is does have several problems. The first drawback is the limited range which typically would be 30 ft or less. The second problem is the fact that Bluetooth does not have enough space to transmit CD-quality audio and therefore the audio is compressed first. Due to the compression, the audio quality will be degraded compared to the original. The final problem is the fact that Bluetooth will introduce a delay in the signal (also called latency) which is a problem when used together with video since the audio will be out of sync or if used in a surround sound setup where some of the speakers would be out of sync with the hard-wired speakers.
Terrestrial digital and satellite radio technologies offer high range but use extensive audio compression and have an audio delay of up to several seconds.
Another technology which is used in wireless audio transmitters from Amphony send the audio digitally without using audio compression. The audio signal will retain CD quality because no audio compression is used. This technology offers an audio latency of less than 1 ms. Therefore these transmitters can be used for wireless speaker kits in a home theater setup and other real-time applications.
This technology is fairly robust against radio interference from other wireless transmitters by using a method called forward error correction. Rather than using the crowded 900 MHz and 2.4 GHz frequency bands, Amphony products operate at 5.8 GHz and thus offer high robustness. Other than Bluetooth, this technology can operate and number of receivers per transmitter which is key for sending audio to several locations throughout the house.
Author Resource:
Brian Fuller has been involved with developing wireless and other electronic devices for over 10 years. You can get further information regarding audio transmitter products and other audio transmitters at Amphony's website.
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