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.
The first form of wireless audio transmission was in the form of AM and FM radio stations. FM radio is still popular today. However, newer technologies have started to replace it. These include DAB broadcasts, satellite and HD radio. Today's wireless consumer devices such as wireless surround sound kits, baby monitors, Bluetooth audio transmitters and wireless microphones eliminate the cord.
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.
The first form of wireless audio transmission was in the form of AM and FM radio stations. FM radio is still popular today. However, newer technologies have started to replace it. These include DAB broadcasts, satellite and HD radio. Today's wireless consumer devices such as wireless surround sound kits, baby monitors, Bluetooth audio transmitters and wireless microphones eliminate the cord.
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.
Let's look at the most traditional technology first: FM broadcasts. FM audio transmitters send the audio by using a high-frequency signal which is constantly changing in frequency according to the audio signal. The technology, which is called frequency modulation (FM), is fairly simple and cost-effective to build and offers high range. Most of today's wireless consumer devices use FM transmission. FM, however, has serious disadvantages compared with newer technologies.
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.
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 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.
Terrestrial digital and satellite radio technologies offer high range but use extensive audio compression and have an audio delay of up to several seconds.
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.
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:
Terrestrial digital and satellite radio technologies offer high range but use extensive audio compression and have an audio delay of up to 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.
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 get further information regarding wireless surround sound kits as well as other wireless audio products from Amphony's website.