In the once smoky, now merely claustrophobic world of professional audio you don’t come across many passive loudspeakers with separate power amps. I’ve visited one exception which proved the rule and that was Abbey Road where B&W were sponsoring the monitoring, but in most instances you get a pair of nearfield monitors on the desk and a bigger set of speakers further away, and both will be actively powered. It makes a lot of sense in that environment because they take up less space and offer more control, and when you are playing at high level all day you want a monitoring system that can take the punishment without sharing the pain. The studio and the PA world is where ATC made its name and where it continues to have fun, designing custom made systems for concert halls and the like. The guys running ATC, Billy Woodman and Bob Polly, give the impression that they don’t give a monkeys about the domestic audio world. But contrarily the company keeps on building variations on its pro themes for us end users and the SCM100SL AT is one of those. It’s a floorstander, or tower version, of the stand mounted active 100 litre three-way that has been in the range for quite a while and which also exists as a pro model. The tower design gets rid of a less than beautiful stand and produces a more substantial looking speaker, real wood veneer extends nearly to the ground where it has a black plinth which accepts spikes or glides if you’d prefer not to nail these heavyweights to your polished wooden floor.
The actual drive units are fixed to a baffle that’s also in black and adds another 34mm to the braced 18mm thickness of the cabinet. This provides an edge for the grille to slide onto, an arrangement that ATC recommends you use when listening because the grille is designed to eliminate diffraction at the sharp baffle edges. ATC makes two the three drive units in this speaker at its facility near Stroud in Gloucestershire, only the tweeter is brought in. ATC started out as a drive unit maker and has continued on this path for the independence and flexibility that it provides.
The tweeter is a 25mm soft dome with a neodymium magnet while the mid is ATC’s classic 75mm dome, a key driver in the company’s range and a fundamental reason why these speakers are so revealing. Like the bass driver it has flat, edge wound OFC wire in a short voice coil that operates in a long magnetic gap for maximum control. Another control factor is the use of massive motor assemblies/magnets combined, in the bass driver, with ATC’s Super Linear rings which sit between the main magnet and the voice coil, the latter suppress eddy currents in the voice coil which allows for increased impedance and in sonic terms a reduction in third harmonic distortion. This is probably why pianos have more body, attack and dynamic range than is usually the case. It’s impossible of course to separate what the drivers contribute from the amplifiers in an active loudspeaker, this like the rest of the Tower range has a 350 watt class A/B tri-amp pack on its back and an electronic crossover between input and amps. The direct connection from power amp to drive unit is the major advantage of active loudspeakers, the amps are tailored exactly to the requirements of the speaker and there are no crossover components between the two. The other side of this coin is that active crossovers are more complex than passive ones which makes it harder to build truly transparent examples. If you want real world dynamics however there is no other route this side of the full range horn that can do the job, and no full range horn that I’ve heard has the bass extension on offer from the 12inch bass driver on this speaker. This monster is the reason for the overall girth of the SCM100SL, that is girth in terms of size and prodigiousness in the bass, if you want to feel the earth move this is the device to achieve that end.
Despite their size they are remarkably easy speakers to accommodate inasmuch as they are not as fussy about placement as the average large passive design. Specifically you can put them quite close to a rear wall and, room shape allowing, this doesn’t result in exaggerated bass. The front firing port helps here as does the fact that they are voiced for transparency and precision rather than flattery, a situation that can give the impression that they are tonally lean. But play a few more pieces and you discover that they merely reflect the original balance with greater accuracy than usual and that some recordings have considerably more low end on them than others. This point gets to the nub of what these speakers are about, the differences between recordings, this rather than fidelity to an oft non existent absolute is what all hi-fi should be about. With purist recordings of acoustic music it’s possible to have some idea of what a high fidelity result might sound like but in all other cases there either is no absolute sound or it’s nearly impossible to know what it is. In a studio recording for instance what you have is a construct made largely on a computer, it might have original instruments on it but the end result is what the producer, engineer and mastering engineer create from those originals. The nearest thing there is to an absolute sound with most contemporary music is what the mastering engineer heard in his studio, a place that has pretty alien acoustics by domestic standards and uses monitors that are more like these ATCs than most domestic loudspeakers. So the scale of difference between the sound of recordings is the best way to differentiate audio components even if this is at odds with aspects of tonality or timing. And on this front this speaker is supreme, the degree of exposure is so great that you have to be very careful that you are not just discovering the limitations of the partnering source and preamp.