Lately a great number of wireless audio devices have appeared such as latest-generation wireless headphones, iPods, cell phones and wireless amplifier devices that promise to cut the cable. I will take a look at whether or not these products keep their promise to provide perfect-quality audio. In addition, I will take a look at the underlying technologies.

A number of products are available with wireless already built in while some others, particularly streaming audio products, frequently have optional wireless capability. Latest generation iPods and cell phones already come with built-in WiFi and Bluetooth support.

The Bluetooth protocol is a fairly low-cost option. Yet, its pitfalls have an impact on high-quality audio applications and are often overlooked.

1) Restricted range

Bluetooth normally just offers a 30 foot range. This is satisfactory for single-room applications. Yet, this limitation does not allow multi-room streaming utilizing Bluetooth.

2) Low data rate - audio compression

Bluetooth reliably supports data transmission rates of about 1 Mbps only which is not sufficient for uncompressed CD-quality audio. Thus Bluetooth utilizes audio compression. The audio will be degraded to some extent due to the audio compression. For this reason higher-end audio equipment normally does not use Bluetooth wireless audio.

3) Signal latency

The audio will experience a delay of a minimum of 10 ms mostly because of the audio compression which is a problem for real-time audio applications but less serious for MP3 players.

4) No support of multiple headphones

Bluetooth cannot stream to numerous headphones at the same time. This might be a dilemma in cases where several people want to listen to the same Bluetooth transmitter.

Uncompressed audio streaming is supported by WiFi. WiFi is a very common protocol. On the other hand, WiFi also has drawbacks in regard to simultaneous transmission to several receivers. As a result of the relatively high power consumption it is rarely used in wireless headphones however. WiFi is convenient for streaming audio from a PC however since almost all PCs have WiFi access.

Wireless speakers and wireless amplifier products for home theater speakers generally utilize their own proprietary protocol. Entry-level wireless headphones and speakers typically still use FM transmission which offers low cost but is prone to noise and audio degradation.

Modern wireless audio protocols avoid audio degradation by utilizing digital transmission. These often also come with mechanisms like forward error correction to deal with interference from other wireless devices.

Newest-generation wireless amplifiers permit streaming to an infinite number of receivers and support uncompressed audio transmission.

The audio latency of these wireless amplifiers is typically between 1 ms and 20 ms. A small-latency amplifier is essential for home theater audio. This assures that all speakers will be in sync. Usually newer generation wireless audio transmitters will work at 2.4 GHz. Some transmitter devices, including Amphony's line of products, work at the less crowded 5.8 GHz frequency band.

Wireless amplifiers offer different levels of audio quality, output power and standby power. Digital Class-D amplifiers offer high power efficiency of no less than 80%. They also have low standby power, usually less than 5 Watts. This reduces heat and keeps them cool during operation. Some digital amplifiers, though, have fairly high harmonic distortion. Audiophile wireless amplifiers offer an audio distortion of 0.05% or less.