A large number of wireless audio transmitter products have emerged over the years. They promise to cut the cord to your audio equipment. We will examine the impact of new technologies on the performance of these products. Also, we'll examine if they keep their promise of eliminating the cable clutter.
AM and FM radio was introduced several decades ago and was the first type of wireless audio transmission. While still being popular today, FM radio is now being replaced by new technologies including HD radio, satellite radio and DAB broadcasts. A range of today's wireless consumer products cut the cord such as wireless surround sound kits, baby monitors, wireless microphones and Bluetooth transmitters.
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 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.
Another technology which has gained popularity recently is called Bluetooth. Bluetooth was originally designed to connect computer peripheral devices wirelessly. Bluetooth will convert he audio into a digital format. This data is then broadcast via the Bluetooth wireless protocol. While offering high robustness against wireless interference, Bluetooth has several problems in regard to audio transmission since it was never designed with the purpose of transmitting audio. The first drawback is the limited range which typically would be 30 ft or less. The second problem is the fact that Bluetooth does not have enough space to transmit CD-quality audio and therefore the audio is compressed first. This compression will result in a loss of audio quality depending on the degree of compression. Bluetooth will introduce a delay or latency to the audio signal which is a problem for surround sound and video applications because the wireless speakers will be out of sync with the remaining speakers and video.
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 transmits the audio signal without compression digitally. This technology is used in wireless audio transmitters from Amphony. The audio signal will retain CD quality because no audio compression is used. The audio latency of this technology is less than 1 ms. Therefore it can be used for real-time applications such as wireless speaker kits in 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.
AM and FM radio was introduced several decades ago and was the first type of wireless audio transmission. While still being popular today, FM radio is now being replaced by new technologies including HD radio, satellite radio and DAB broadcasts. A range of today's wireless consumer products cut the cord such as wireless surround sound kits, baby monitors, wireless microphones and Bluetooth transmitters.
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 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.
Another technology which has gained popularity recently is called Bluetooth. Bluetooth was originally designed to connect computer peripheral devices wirelessly. Bluetooth will convert he audio into a digital format. This data is then broadcast via the Bluetooth wireless protocol. While offering high robustness against wireless interference, Bluetooth has several problems in regard to audio transmission since it was never designed with the purpose of transmitting audio. The first drawback is the limited range which typically would be 30 ft or less. The second problem is the fact that Bluetooth does not have enough space to transmit CD-quality audio and therefore the audio is compressed first. This compression will result in a loss of audio quality depending on the degree of compression. Bluetooth will introduce a delay or latency to the audio signal which is a problem for surround sound and video applications because the wireless speakers will be out of sync with the remaining speakers and video.
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 transmits the audio signal without compression digitally. This technology is used in wireless audio transmitters from Amphony. The audio signal will retain CD quality because no audio compression is used. The audio latency of this technology is less than 1 ms. Therefore it can be used for real-time applications such as wireless speaker kits in 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 transmitters and other wireless audio products from Amphony's website.
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