The SurroundBar hails from the same school of thought as Yamaha's YSP single speaker surround sound system but cracks its virtual nut in a very different way. Unlike the Yamaha, the SurroundBar uses larger, traditional drivers in the box and applies what the company terms SDA processing.

This is a heady mix of psychoacoustic and geometric processing designed to create a three-dimensional soundfield without rear speakers or all that messy bouncing sound off of walls.

The SurroundBar is also a completely passive device, meaning it needs a high-level five-channel feed from an AV amplifier and a DVD player to make it sing.

Considering it is about £200 more than the Yamaha YSP-800, on paper at least it doesn't appear particularly good value for money. But in the flesh you can see where the cash is being spent.

It is gorgeously crafted from extruded aluminium and contains seven 89mm bass/midrange drivers and seven 19mm soft dome tweeters. It is fully shielded for placement near CRT TVs and comes with wall and table mounts, plus a dedicated five-channel speaker cable with a flat profile for sleek installation.

If you do want to add a subwoofer - and I would certainly recommend one - Polk suggest using high-level inputs hooked up to the SurroundBar's L/R speaker inputs.

Speaker distances should be matched across all five channels and levels should be tweaked towards the rear between 3db and 6dB for best results, says Polk. By trial and fairly spectacular error I also discovered that it's best to leave EQ systems designed to setup traditional 5.1 speaker systems switched off too.

Rich and robust

From the outset the sound is rich and robust, the larger main drivers clearly punching further down the frequency spectrum. Voicing has a pleasing mid-range, which makes for very well balanced dialogue with little speaker signature.

Ultimate volume is good for the genre of single-box surround systems, and the more you listen to the Polk the seemingly more invisible it becomes as part of your home cinema entertainment. In terms of surrounding you with sound the effects are, well, interesting.

In terms of accurate channel steering and perfect placement - forget it, it really doesn't happen. However, it does manage to create a suitably enveloping overall ambience of effects that are far less influenced by the room, and where you sit in it, than other systems here.

For examples, the ships in the opening battle sequence of Revenge of the Sith have definite presence around the room, but you can't physically track a flight path from the pot plant in one corner to the door in the other.

The more you listen to the Polk the more you slip into listening to the film and getting involved in the plot - and that is a trick not many systems manage so comprehensively. The balance is right, the voicing is right and the sound has probably the best scale and impact I have heard from a single hang-on-the wall speaker to date, although a subwoofer is all but essential to get cinema sound at its best.

Its only weakness is that price ticket. At £850, plus an AV amplifier, plus a subwoofer, plus a DVD player, one's wallet is in for a serious ravishing. For the same amount of moolah you could have a very competent and superior-sounding full 5.1 loudspeaker system. Then again, if space, décor or spouses are a problem and money isn't, the SurroundBar is probably the ultimate one-box speaker solution I've heard to date.