Vintage Electronics

Music Without Cable Clutter? – The Latest Generation Of Wireless Audio Transmitter Gadgets

Eliminating the big clutter of cords has lead to a variety of wireless audio transmitter devices over the years which claim to untie your home audio equipment. We will investigate the impact of new technologies on the performance of these products. In addition, we’ll investigate if they keep their promise of removing the cable clutter.

Wireless transmission of music has started with the launch of commercial radio broadcasts several decades ago. FM radio is still popular today. However, newer technologies have begun to replace it. These include DAB broadcasts, satellite and HD radio. Today’s wireless consumer devices such as wireless speaker kits, baby monitors, Bluetooth audio transmitters and wireless microphones eliminate the cord.

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. Not every technology is ideal 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 simpleness and thus cost as well as range. Most of today’s wireless consumer products utilize FM transmission. FM, however, has serious disadvantages in comparison with new technologies.

The FM signal will pick up hiss. Therefore there will be noticeable background noise. The amount of static will depend on the position 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. Using two antennae is one approach some devices use to cope with this problem (diversity receivers). In addition, FM transmissions will easily pick up interference from other wireless devices.

Bluetooth based audio transmitters have gained popularity recently. Bluetooth is a common wireless protocol which was designed primarily as an interface between computer peripheral products. 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 a number of pitfalls in regard to audio transmission since it was never designed with the purpose of transmitting audio. Bluetooth only offers a range of 30 ft or less and will compress the audio since it does not offer enough space to broadcast an uncompressed CD-quality signal. As a result of the audio compression, the audio quality will decrease. Bluetooth will introduce a delay or latency to the audio signal which is a drawback 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 which is used in wireless audio transmitters from Amphony sends the audio digitally without using audio compression. The signal will retain the original quality by avoiding audio compression. This technology offers an audio latency of less than 1 ms. Consequently 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. The Amphony transmitters operate at 5.8 GHz. This frequency space is less crowded than the 900 MHz or 2.4 GHz bands consequently 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 house.

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This entry was posted on Monday, June 4th, 2012 at 6:13 pm and is filed under Vintage Electronics. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.