One of the easiest ways to improve the sound quality of a desktop or laptop PC is to use better speakers. Even if you don't have a 5.1, 6.1 or 7.1-channel sound card in your machine, you can get much better results with a good 2.1 system than with any internal speakers. Altec Lansing's FX4021 set uses a novel speaker arrangement to produce good sound from the standard mix of a sub-bass unit and twin mid- and high-frequency satellites.

The twin speaker units in the sub-bass enclosure - which is as large as a small, black paper basket - are mounted face-to-face in an isobaric arrangement. Isobaric, or constant pressure, speaker systems are designed to increase the bass range in a given size of cabinet, by using two speakers rather than one. By mounting them one behind the other to create a constant-pressure zone between them, they should gain an increased bass range of up to an extra half-octave, compared with single-speaker designs.

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The strange thing here is that whereas most isobaric arrangements put the speakers one behind the other in cone-to-magnet or magnet-to-magnet designs, Altec Lansing mounts them vertically, cone-to-cone, so the sound emanates from the back of the cones. You would think the structure of each speaker - the frame holding the cone in place - might obstruct the sound coming from its back. In practice, the 24W sub-bass unit works very well, giving a strong bass line to music and an impressive punch to explosions in movies and games.

The two 11W satellites are mounted on cast metal stands and include both 40mm mid-range and 18mm high-frequency drivers, which play through thin, black-metal meshes. These complement the bass unit well, adding a good level of detail to speech, singing and treble instruments. They don't quite have the presence of systems like the Acoustic Energy Aego-M, but they're less than half the price of these, our current favourite PC speakers.

Controls of the FX4021 can be operated from the wired control pod or a wireless remote and the control pod enables you to plug a media player, such as an iPod, into the speakers without disturbing the connection from your PC. Control involves selecting a setting - volume, tone or the stereo image controlled by Altec Lansing's SFX software - and adjusting the level with a digital click-wheel. This is a logical technique and works well to tweak sound characteristics when switching between sources.

This is a smart set of speakers using a novel bass speaker design, which gives a good thumping bass while not overpowering the mid-range and treble frequencies provided by the two reasonable satellites. While not in the true hi-fi class, the FX4021 speakers are more than reasonable for music, games and movie soundtracks.