Eliminating the big clutter of cables has lead to a variety of wireless audio transmitter products over the years which promise to untie your home audio equipment. We will take a look at recent products to see whether they can deliver on their promise to eliminate the cable clutter and we'll examine how changing technology has impacted performance of these products.
Wireless transmission of music has started 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 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.
One of the main application for wireless audio is to distribute music throughout the home and setting up speakers without running speaker cables which is a big problem in homes that 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 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. While most of today's 900 MHz products use FM transmission, FM has some major problems.
FM transmissions will pick up static which is noticeable as a background hiss depending on the location of the wireless receiver. The reason for the varying quality is a phenomenon called multipath fading which is a result of reflected radio waves cancelling each other out. Some wireless FM transmitters use two antennae in an attempt to cope with this phenomenon (diversity receivers). In addition, FM transmissions will easily pick up interference from other wireless devices and products.
Bluetooth has gained popularity recently for wireless audio transmission even though this protocol was primarily designed to connect computer peripherals. Bluetooth audio transmitters will convert the audio signal to digital information and then transmit via the Bluetooth protocol. Bluetooth is fairly robust in terms of interference in is well standardized. Bluetooth, however, has some problems in regard to wireless audio since it was not designed for wireless audio originally. The range of the transmission is only 30 ft or less. Also, Bluetooth does not have enough space to send an uncompressed CD-quality audio signal. Therefore the audio is compressed prior to the transmission. As a result of the audio compression, the audio quality will decrease. 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.
The technology used in Amphony's wireless audio transmitters sends audio in a digital format without audio compression. By avoiding audio compression, the signal will retain the original quality. 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.
To be robust against interference from other wireless devices, this technology uses forward error correction. This mechanism can repair errors during the transmission. 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. 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.
Wireless transmission of music has started 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 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.
One of the main application for wireless audio is to distribute music throughout the home and setting up speakers without running speaker cables which is a big problem in homes that 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 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. While most of today's 900 MHz products use FM transmission, FM has some major problems.
FM transmissions will pick up static which is noticeable as a background hiss depending on the location of the wireless receiver. The reason for the varying quality is a phenomenon called multipath fading which is a result of reflected radio waves cancelling each other out. Some wireless FM transmitters use two antennae in an attempt to cope with this phenomenon (diversity receivers). In addition, FM transmissions will easily pick up interference from other wireless devices and products.
Bluetooth has gained popularity recently for wireless audio transmission even though this protocol was primarily designed to connect computer peripherals. Bluetooth audio transmitters will convert the audio signal to digital information and then transmit via the Bluetooth protocol. Bluetooth is fairly robust in terms of interference in is well standardized. Bluetooth, however, has some problems in regard to wireless audio since it was not designed for wireless audio originally. The range of the transmission is only 30 ft or less. Also, Bluetooth does not have enough space to send an uncompressed CD-quality audio signal. Therefore the audio is compressed prior to the transmission. As a result of the audio compression, the audio quality will decrease. 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.
The technology used in Amphony's wireless audio transmitters sends audio in a digital format without audio compression. By avoiding audio compression, the signal will retain the original quality. 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.
To be robust against interference from other wireless devices, this technology uses forward error correction. This mechanism can repair errors during the transmission. 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. 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.
About the Author:
Gunter Fellbaum has been designing audio and electronic products for over 10 years. You can get further information about wireless surround sound kits as well as other wireless audio products from Amphony's website.
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