Eliminating the big pipe length has led to a range of wireless audio transmitters over the years promising to unload your home audio equipment. We will look at the latest products to see if they can deliver on their promise to eliminate the cable and we investigate how technology switching has affected the performance of these products.
Wireless music transfer has begun with the launch of commercial radio broadcasts several decades ago. 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 replacing traditional FM radio. Today, a variety of consumer devices like wireless microphones, wireless surround sound sets, Bluetooth audio transmitters, child monitors, etc. that eliminate the cord by transmitting audio wirelessly.
One of the most important applications for wireless audio is to distribute music all over the home and configure speakers without speaker cables, which is a major issue in homes that are not connected to audio. Not all technologies are perfect for wireless audio that we will find out.
Lets look at the most traditional technology first: FM broadcasts. FM audio transmitter transmits the sound using a high frequency signal that is constantly changing in frequency according to the 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 scope. As a result, most of todays 900 MHz wireless earphones use FM transmission. But FM has some major drawbacks.
The first is the fact that the transfer will pick up audio and thus it will be slightly elevator or static. The amount of noise will actually vary depending on the location of the radio or receiver. This is because the radio signal jumps off walls and will interrupt at different locations. This phenomenon is called multi-way fading. Some wireless FM transmitter uses two antennas in an attempt to handle this phenomenon (diversity receiver). In addition, FM transmissions can easily get interference from other wireless devices and products.
Bluetooth-based audio transmitters have become popular recently. Bluetooth is a popular wireless protocol, designed primarily as an interface between peripherals for computers. Bluetooth audio transmitter converts the audio signal into digital information and then transmits via the Bluetooth protocol. Bluetooth is quite robust when it comes to interference you are well standardized. However, Bluetooth has some issues with wireless audio because it was not originally designed for wireless audio. The first disadvantage is the limited range that would normally be 30 ft or less. The other problem is the fact that Bluetooth does not have enough space to transfer CD quality audio and therefore the audio is first erased. This compression results in loss of audio quality depending on the degree of compression. The last problem is the fact that Bluetooth will introduce a delay in the signal (also called latency) which is a problem when used with video because the audio will be unsynchronized or if it is used in a surround sound set-up where some of the speakers would be synchronized with the speakers.
Satellite radio and digital terrestrial radio technology offer high-quality but uses extensive audio compression that leads to audio degradation and has a multi-second audio delay.
Newer technology transmits digital audio without compression. By avoiding audio compression, the signal retains the original quality. The audio delay of any of these products is less than 1 ms and therefore these technologies are also used in wireless speaker kits for home theater systems.
By using error correction, these technologies can handle interference from competing wireless devices that are crucial in todays noisy environment. Some transmitters work at 5.8 GHz. This frequency range is less crowded than 900 MHz or 2.4 GHz bands, which leads to further improvement in reliability. Unlike Bluetooth, a number of wireless receivers can work from a single wireless audio transmitter, which is a problem when distributing audio to multiple rooms in a home.