A large number of wireless audio transmitter products have emerged over the years. They claim to cut the cables to your audio equipment. Can these products make good on their promise to eliminate the cable clutter? What influence has changing technology had on their performance?

The first form of wireless audio transmission was in the form of AM and FM radio stations. FM radio is still popular until today even though some new technologies such as satellite radio and digital radio formats such as HD radio and DAB radio have started 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 cut the cord by transmitting audio wirelessly.

Setting up speakers in another room and distributing music throughout the house are some of the applications of wireless audio. Many homes are not wired for audio. Not every technology is perfect when it comes to wireless audio as we will find out.

One of the most traditional technologies is FM broadcasting. Audio is transmitted via a radio-frequency signal which is modulated (changed in frequency) with an audio signal. This technique is called frequency modulation or FM for short. The biggest advantage of FM transmitters is their simplicity and thus cost as well as range. Most of today’s wireless consumer products utilize FM transmission. FM, however, has serious disadvantages in comparison with modern technologies.

FM transmissions will pick up noise which is noticeable as a background hiss based on the position of the wireless receiver. This is due to the fact that the radio signal is bouncing off walls and will cancel itself out at different locations. This phenomenon is known as multi-path fading. One method to deal with this problem is employing two antennae instead of one. Products utilizing this technique are called diversity receivers. FM radios will easily pick up interference from other consumer products which is another problem.

Bluetooth based audio transmitters have gained popularity lately. Bluetooth is a popular wireless protocol which was designed primarily as an interface between computer peripheral products. 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. On the other hand, Bluetooth was not designed for audio transmissions. Therefore is does have several problems. The first downside is the limited range which typically would be 30 ft or less. The next problem is the fact that Bluetooth does not have sufficient room to transmit CD-quality audio and as a result the audio is compressed first. As a result of the audio compression, the audio quality will decrease. Another problem is that Bluetooth will cause a delay or latency to the signal during the broadcast. This delay is a particular drawback for video and surround sound applications. In these applications the sound from the wireless speakers would be out of sync with the video and remaining speakers.

The technologies used for satellite radio and terrestrial digital radio offer high range. However, they also use extensive audio compression. Further, a delay of up to several seconds is introduced.

The technology used in Amphony’s wireless audio transmitters sends audio in a digital format without audio compression. The signal will preserve the original quality by avoiding audio compression. The audio latency of this technology is less than 1 ms. As a result it can be used for real-time applications such as wireless speaker kits in home theater setups.

By using error correction, this technology can deal with interference from competing wireless products which is important in today’s noisy environment. Amphony products use the 5.8 GHz frequency band which is less crowded than the 900 MHz and 2.4 GHz bands. The result is high reliability. An advantage over Bluetooth is the ability to send audio to any number of wireless receivers from a single transmitter. This is important for distributing audio to several rooms in the home.

Filed under: Technology by admin
No Comments »