The latest series of wireless audio transmitter devices promises streaming of music throughout the home without limits. We will look at various products and technologies to find out in how far these devices are effective for whole-house audio applications and what to look out for when buying a wireless system.

Infrared wireless audio devices are restricted to line-of-sight applications, i.e. only function within a single room because the signal is sent as infrared light which can't penetrate walls. This technology is often found in wireless speaker kit products.

RF wireless music devices broadcast the music signal via radio waves. These radio wave signals can without difficulty go through walls. The signal is broadcast either by utilizing FM transmission or digital transmission. FM transmission is cheap but quite prone to static, audio distortion and susceptible to interference.

Digital wireless audio transmitter devices, such as products from Amphony, make use of a digital protocol. The audio is first converted to digital data before being broadcast. This method guarantees that the audio quality is fully preserved. Some transmitters utilize some form of audio compression, such as Bluetooth transmitters, which will degrade the audio to some degree. Transmitters which send the audio data uncompressed will achieve the highest fidelity.

Wireless LAN (WLAN) products are practical when streaming from a PC but will add some amount of latency or delay to the signal because wireless LAN was not originally designed for real-time audio streaming. WLAN receivers ordinarily require buying a separate LAN card to be plugged into every receiver.

Powerline products send the audio via the power mains and offer great range. They run into problems in homes where there are individual mains circuits in terms of being able to cross over into another circuit. Also, these products build in a delay of a number of seconds to safeguard against transmission errors during power surges and spikes which prevents their use in applications where the audio from wireless loudspeakers has to be in sync with other non-wireless speakers or video.

Here are some recommendations for picking the optimum wireless audio system: Try to find a system that can run several wireless receivers from a single transmitter. Ideally an unlimited number of receivers should be supported. That way you don't need to buy extra transmitters when you start adding receivers in several rooms of your house. Some devices have some form of error correction built in which will help guard against dropouts in case of strong wireless interference. Choose a digital RF audio transmitter to guarantee that the audio quality is preserved. Make sure the audio delay is smaller than 10 ms if you have a real-time application such as video.

Select a transmitter that has all of the audio inputs you need, e.g. speaker inputs, RCA inputs etc. Get a wireless system where you can buy separate receivers later on. You should confirm that you can get receivers for all the different applications you have. Such receivers may include amplified receivers for passive speakers or line-level receivers for active speakers. Select a transmitter that can regulate the audio volume of the input stage. This will give you the flexibility to connect the transmitter to any kind of equipment with different signal levels. Otherwise the audio may get clipped inside the transmitter converter stage or the dynamic range is not fully utilized.

Check that the system provides amplified receivers with a digital amplifier to ensure high power efficiency. This will help keep the receiver cool during operation. Also, make sure the amplifier provides low audio distortion. This is vital for good sound quality. Verify that the amplified receiver is able to drive speakers with the preferred Ohm rating and that it is small and easily mountable for simple installation. Products using the less crowded 5.8 GHz frequency band will normally have less trouble with wireless interference than 900 MHz or 2.4 GHz products.