Harman Kardon GLA-55 speakers

Some speakers are destined to blend discreetly into your environment. Not so the Harman Kardon GLA-55, whose multi-faceted-diamond looks are positively shouting for attention.

Each Harman Kardon GLA-55 speaker is based on a traditional two-way driver design, comprising a concave metal 52mm mid-bass driver and metal-domed tweeter, shoehorned into a totally transparent case resembling an alien crystal skull.

The tweeters carry chromed bars to discourage idle prodding of the delicate domes. And built into the case are the system's amplifiers, hidden away in the base plate.

You connect the speakers to a computer or iPod via a 3.5mm stereo jack plug in the right-hand speaker. Electrical power also comes into this master speaker from a laptop-style power supply. Under the main drivers is a reflex port which helps improve acoustic efficiency and low-frequency response.

As well as the usual volume control on your music player, there are touch-sensitive + and - buttons on the right Harman Kardon GLA-55 speaker, sat between drive units. White LEDs are hidden in each speaker's base, pulsing when in standby mode and steady-on when in use.

Try to lift a Harman Kardon GLA-55 speaker and you may be surprised at their weight. They really are very solid and hefty feeling. If you peer inside the transparent sides you can see the U-shaped reflex port curving through the bodies up to the tweeter, as well as polished metal internal parts of all the drive units. What you can't see is any obvious cable wiring, as this seems to be handled by thin metallic rods that join the drivers.

The GLA-55 speakers not only look but feel like no traditional hi-fi speaker. They are incredibly dense and seem non-resonant. The absence of wood cabinet and parallel internal walls means the familiar colourations of a hi-fi box speaker are entirely absent. In fact, the crazy shape with faceted external sides and curved interior really should reduce the usual resonances that can cloud the sound.

Digital Signal Processing

To optimise sound quality, the GLA-55 system uses digital signal processing (DSP).

Analogue audio signal input is converted to 24-bit/48kHz digital, then passed to a 24-bit DSP, responsible for equalisation and dynamic limiting, gently contouring bass and treble levels to suit the speaker's limited size.

Some compression and limiting here also serves to prevent either the amplifiers or drive units from being overdriven into gross distortion at high volume levels or when presented with high levels of bass.

Four separate channels of 26-watt MOSFET Class D amplifiers are included, two for each speaker and dedicated to each treble and mid-bass drive unit, with active crossovers to split the signal at the DSP stage.

Sound quality of the Harman Kardon GLA-55 is, ahem, clearly impressive. Despite their modest size - by the standards of regular hi-fi loudspeakers, rather than iPod docks - the GLA-55 speakers sound much bigger and fuller than you might expect.

There's no proper subterranean bass of course, yet the subtle tailoring of sound by Harman Kardon's engineers means you do get a great sense of a weighty low-frequency response. Class D amplifiers are rarely lauded by audiophiles, but in the context of these Harman Kardon GLA-55 speakers we still heard a clean and impressively accurate rendering of music.

In music with little bass content they could sound a little clinical, a result of the relatively neutral voicing and 'digital' amps, along with low-resonance cabinets that aren't adding much of their own unwanted signature. A retro valve amp sound is not in the Harman Kardon GLA-55's repertoire. But they can do well-paced dance and pop very well, never sounding strained or stressed even when propelling bass from their long-throw drivers.

Top frequencies could be a tad metallic in character but this was tempered by strong bass fundamentals and a midband that neither unduly projected vocalists nor left them shy at the back of the mix.

Compared to another top-spec PC/iPod speaker system, the Bowers & Wilkins MM1, the Harman Kardon GLA-55 speakers don't show their inner digital processing quite so much when limiting dynamic peaks. And top volume is also noticeably expanded. At close to twice the price of the B&Ws, the expectation may be for a more mature and encompassing sound. And for that expanded sound quality with incredible freedom from chestiness they will not disappoint.