Although ATC (Acoustic Transducer Company - based in a picturesque location in rural Gloucestershire) enjoys strong brand recognition in the professional domain of recording studios, the brand is largely unknown to users of domestic home cinema and multichannel audio.

So for those who don't know, a measure of ATC's serious multichannel intent can be gleaned from the fact that the company produces no less than six separate multichannel Concept Collections, ATC speak for speaker packages, four of which are fully active (ie self-powered).

The Active Concept 5, reviewed here, is the penultimate ATC package, at a decidedly serious £11k all in, though buyers should remember that there may be system savings in eliminating a costly multichannel amplifier in favour of a processor/preamp.

Like other ATC systems, however, each of the speaker models is available piecemeal, and with discretion (ie avoiding wild size mismatches etc) can be mixed and matched with any of the other Concept speakers, all of which are designed with common voicing and dispersion in mind. Note also that the system is available to order rather than from stock: your dealer will advise on delivery timetables, and any customisation required to match specific listening room or system requirements.

Seriously active

As I indicated, this is a very serious system. The four Active 20 satellites are relatively user friendly, and will not overwhelm larger rooms. ATC specifies room sizes of around 50 square meters for their use, but this is not a hard and fast rule. But they are heavy, and will need to be dispersed on rugged pedestal stands to ensure the tweeters sit around ear level.

They also need to be positioned a minimum of, say, 30cm proud of the nearest walls. You'll need considerable space to make the most of this set. Each Active 20 is equipped with a 150mm bass unit and a 25mm soft dome tweeter, with an onboard 200W amplifier in charge of the bass, and a 50W amplifier for the treble. Build quality is superb. The large area side walls of the enclosure are not parallel to avoid standing wave resonances.

The huge, curved C5CA centre speaker is fashioned from the same mould, but in this case there are two 150mm bass/mid drivers, and although the amplifier complement is similar, the speaker is a real back breaker at 45kg. Finally, the C4 subwoofer is a large, glossy, downwards firing design with an enclosed plinth which is fitted with a 30cm driver and a 1kW amplifier.

This is subwoofer design on a grand scale, but in practice it is easily matched to the rest of the system using a 'contour' control (essentially a mid bass tone control) in addition to the usual low pass filter, which with this system is optimally set around 70Hz. All speakers are equipped with XLR balanced inputs, which in this case were wired back to a reference Lexicon processor using phono-XLR adaptor leads.

Although designed to meet the requirements of a professional multichannel mastering suite, the ATC system is well dressed for domestic duties, with sober but high quality surface finishes and excellent detailing.

The massive perforated front grills on the satellites however are a bit of a giveway. They might not withstand nuclear Armageddon, but anything short should be OK. Much the same applies to the combination of drive units and amplifiers.