Introduction and Power Rating
A Blu-ray deck and hi-def TV provide a perfectly serviceable way of watching movies, but a home cinema it is not - the only way to achieve pure cinematic sonic bliss is to add a surround sound system. These come in a variety of guises across a wide range of prices - all-in-one packages provide a quick, easy and cost-effective way of getting all the gear you need in one fell swoop, but it's often at the expense of performance. For the best sound quality, separates (i.e. an AV receiver and a 5.1/7.1 speaker system) are the way to go. They may cost a little more than a one-box job, but the results are often worth the extra investment.
Whichever route you take, you'll be faced with a barrage of features and jargon that can make it hard to sort the essential from the irrelevant. And that's where we come in - in this two-part guide, we tell you what features you should be looking for when buying an AV receiver and speakers, and explain clearly some of the terms you're likely to encounter.
First up it should be explained that the difference between AV receivers and amplifiers is that receivers come with a built-in radio tuner, as well as all the necessary sound processors and amplifiers. Over the years the word "receiver" has taken on a whole new meaning with the latest models acting as a hub for a wide range of audio formats and devices.
Amplifier power rating
This tells you the amount of amplification the receiver will provide for each channel in the system, expressed in watts (e.g. 5 x 110W). The majority of AV receivers offer 5.1-channel amplification, which means they amplify the left, right, centre, surround left and surround right channels, as well as providing a low-frequency effects output that's sent to a powered subwoofer (the ".1" in 5.1). This LFE channel is usually sent as an unamplified "line-level" signal which is amplified by the subwoofer. 7.1-channel receivers provide two extra channels of amplification for the left/right surround back (or left/right Front Height for Dolby Pro Logic IIz and Audyssey DSX-capable models - see Sound modes on Page 2 of this article).
If movies are your main concern, check that the power rating provided is with all channels being driven to get a more accurate idea of the unit's power - if only one or two channels are used the figure is likely to be higher and many not reflect what you get when you play a multichannel movie. The most common types of amplifier found inside AV receivers are Class AB and Class D, the latter are smaller and more efficient and therefore allows receivers using them to be smaller and lighter.
The reason you need to consider the receiver's power rating is that it's no good buying a powerhouse receiver that blasts out 200W per channel for a poky living room. Likewise if you're room is huge you'll need a receiver powerful enough to fill it. But you also need to make sure that the speakers you want to pair it with are capable of handling the power being supplied.