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.
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. The technologies used today all have pros and cons as we will examine.
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.
The first is the fact that the transmission will pick up noise and thus there will be some hiss or static. The amount of noise will actually vary depending on the location of the radio or 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 called multi-path fading. Using two antennae is one method some devices cope with this problem (diversity receivers). Another problem is that FM radios easily pick up interference from competing wireless transmitters.
Bluetooth based audio transmitters have gained popularity recently. Bluetooth is a popular wireless protocol which was designed primarily as an interface between computer peripheral products. Before the signal is broadcast, Bluetooth transmitters will convert the audio into a digital format. 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. Bluetooth only offers a range of 30 ft or less and will compress the audio since it does not offer enough space to transmit an uncompressed CD-quality signal. Due to the compression, the audio quality will be degraded compared to the original. Another problem is that Bluetooth will introduce a delay or latency to the signal during the transmission. This delay is a particular problem 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.
Satellite radio and digital terrestrial radio technologies offer high range but use extensive audio compression leading to degradation of the audio signal and have an audio delay of several seconds.
Another technology which is used in wireless audio transmitters from Amphony send the audio digitally without using audio compression. The signal will retain the original quality by avoiding audio compression. The audio latency of these products is less than 1 ms and therefore this technology is also used in wireless speaker kits for home theater setups.
By using error correction, this technology can cope with interference from competing wireless devices which is key in today's noisy environment. The Amphony transmitters operate at 5.8 GHz. This frequency space is less crowded than the 900 MHz or 2.4 GHz bands thus leading to a further improvement of reliability. In contrast to Bluetooth, any number of wireless receivers can operate from a single wireless audio transmitter which is a concern when distributing audio to several rooms within a home.
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.
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. The technologies used today all have pros and cons as we will examine.
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.
The first is the fact that the transmission will pick up noise and thus there will be some hiss or static. The amount of noise will actually vary depending on the location of the radio or 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 called multi-path fading. Using two antennae is one method some devices cope with this problem (diversity receivers). Another problem is that FM radios easily pick up interference from competing wireless transmitters.
Bluetooth based audio transmitters have gained popularity recently. Bluetooth is a popular wireless protocol which was designed primarily as an interface between computer peripheral products. Before the signal is broadcast, Bluetooth transmitters will convert the audio into a digital format. 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. Bluetooth only offers a range of 30 ft or less and will compress the audio since it does not offer enough space to transmit an uncompressed CD-quality signal. Due to the compression, the audio quality will be degraded compared to the original. Another problem is that Bluetooth will introduce a delay or latency to the signal during the transmission. This delay is a particular problem 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.
Satellite radio and digital terrestrial radio technologies offer high range but use extensive audio compression leading to degradation of the audio signal and have an audio delay of several seconds.
Another technology which is used in wireless audio transmitters from Amphony send the audio digitally without using audio compression. The signal will retain the original quality by avoiding audio compression. The audio latency of these products is less than 1 ms and therefore this technology is also used in wireless speaker kits for home theater setups.
By using error correction, this technology can cope with interference from competing wireless devices which is key in today's noisy environment. The Amphony transmitters operate at 5.8 GHz. This frequency space is less crowded than the 900 MHz or 2.4 GHz bands thus leading to a further improvement of reliability. In contrast to Bluetooth, any number of wireless receivers can operate from a single wireless audio transmitter which is a concern when distributing audio to several rooms within a home.
About the Author:
Gunter Fellbaum has been designing audio and electronic products for over a decade. You can get additional information concerning wireless surround sound transmitters and other wireless audio products from Amphony's website.
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