When you don’t want, or can’t fit, six large speakers in your movie room, a sub/sat system is a stylish, compact solution that can deliver a big surround experience writes Thomas Bartlett.

One unfortunate side effect of home theatre has been the proliferation of loudspeakers. Two was all you needed during the glory years of stereo, from the late 1950s to the late 1990s. But then came the DVD with Dolby Digital 5.1 and DTS 5.1, and now new 7.1 systems.

So where do you put all your loudspeakers? And will there still be room for you in the lounge room?

These potential problems can be solved with three words: subwoofers and satellites. But, as we shall see, these need not merely be space savers. Some systems offer sonic advantages over even very high-quality full range loudspeakers.

What are subwoofers and satellites?

The intended use of the subwoofer in a home theatre system is to deliver the 0.1 channel, otherwise known as the Low Frequency Effects or LFE. This dedicated bass track, included in Dolby Digital and DTS soundtracks, covers a frequency range from a shockingly low 3 hertz up to 120 hertz. Fortunately, moviemakers typically don’t put in sounds that deep. After all, we cannot hear anything much below about 20 hertz. But some do put plenty of really deep stuff in there.

Just because there is a special channel in modern movie sound for low frequencies does not mean that all the low frequencies are confined to it. In fact, all the channels in Dolby Digital and DTS are specified to carry the same deep bass sounds. When mastering the sound for movies, the engineers usually only put the explosions, the stampeding herds and such-like in the LFE channel. The bass drum from the orchestral soundtrack usually goes in the main channels.

That’s why you have to tell your home theatre receiver whether you have a ‘large’ or ‘small’ loudspeaker in each position.

So your subwoofer has a secondary purpose: to deliver the bass from those channels where your speakers are too small to handle it themselves. The home theatre receiver manages all this for you, once you tell it which speakers are which. Those you set as ‘small’ have their signals divided into bass, and all the rest. The subwoofer gets the bass and the small speaker gets all the rest.

Satellite speakers are an extension of this. Instead of small speakers, you have tiny speakers. Most regular speakers, including bookshelf models, are designed to at least attempt to reproduce bass because the manufacturers don’t know whether you’ll have a subwoofer or not. Satellite speakers are specifically designed to omit all deep bass, and most mid-bass.

So they can be much smaller than even bookshelf speakers, and normally offer just two speaker drivers in each: a ‘bass’/midrange, which is rarely bigger than 100 mm in size, and a tweeter. Some brands get away with a single driver, omitting the tweeter.

Canadian brand PSB may not be well known, but is loved by audiophiles. The PSB Alpha Intro HT sub/sat system may not look much, but it sounds glorious. RRP $1,599.