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.
FM transmitters are using the most traditional technology in which audio is sent by changing the frequency of a radio-frequency carrier. This technology is called frequency modulation or FM. It is fairly simple to implement. Thus FM transmitters are very cost-effective. Also, FM transmission offers high 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. FM radio waves are often reflected by walls and obstacles. This will cause several components to cancel each other out thus causing a varying signal quality in different locations. This phenomenon is called multipath fading. One method to cope with this problem is using two antennae instead of one. Products using this method are called diversity receivers. FM radios will easily pick up interference from other consumer devices which is another problem.
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.
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.
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.
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. 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 multiple rooms in the 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.
FM transmitters are using the most traditional technology in which audio is sent by changing the frequency of a radio-frequency carrier. This technology is called frequency modulation or FM. It is fairly simple to implement. Thus FM transmitters are very cost-effective. Also, FM transmission offers high 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. FM radio waves are often reflected by walls and obstacles. This will cause several components to cancel each other out thus causing a varying signal quality in different locations. This phenomenon is called multipath fading. One method to cope with this problem is using two antennae instead of one. Products using this method are called diversity receivers. FM radios will easily pick up interference from other consumer devices which is another problem.
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.
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.
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.
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. 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 multiple rooms in the home.
About the Author:
Gunter Fellbaum has been designing audio and electronic products for over 10 years. You can find further information concerning wireless surround sound kits and other wireless audio products from Amphony's website.
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