ATC SCM20ASL active speakers
ATC have long been advocates of active loudspeakers – their SCM50ASL is possibly the most popular example at the serious end of the market and for good reason. I used to use the substantial SCM150A actives as a reference but I haven’t had an active two-way standmount at home, so when the SCM20ASL was launched an opportunity was grasped. This is the first active two-way standmount that ATC have made since the SCM20-2 was launched in the late nineties. That model had a more elaborate (ie expensive) heat sinking system and cabinet but shared the six-inch mid/bass driver seen here. A limited edition of the SCM20ASL was launched prior to this version and just a few pairs remain available.
What’s the deal with active speakers?
In passive speakers the crossover, which splits the signal into frequencies for the various drivers, sits between the amplifier and the drive units. The crossover therefore has to have relatively high power handling and its presence makes it more difficult for the amp to control the drive units themselves. In an active speaker the crossover is a powered electronics device and sits between the preamp and the power amp, therefore it operates at line level and only has to deal with signals up to a couple of volts. The power amps in an active speaker are connected directly to each drive unit and therefore have considerably greater ability to control them.
Another advantage is that electronic crossovers allow the designer more freedom. For a start there is no need to second guess the nature of the amplification as is the case in passive speakers: the crossover’s characteristics don’t change with level as the power handling factor is not an issue. ATC includes an all-pass filter in its active crossovers, which allows for the phase response to be optimised through the crossover point, something that is very difficult to achieve with passive designs and rarely seen. Dynamic range is also enhanced in active designs because the crossover is placed before the power amplifier so no energy is wasted in lossy passive components.
With so much going for them, you’d think that active speakers from ATC and others would be much more popular, but the snag is that you cannot usually upgrade the power amps, which, for the seasoned audiophile (and his dealer), is a limitation. However, for those seeking high sound quality in a compact form they have an awful lot to offer, and the fact that so many studios use active speakers suggests that they have clear advantages.
The SCM20ASL is a meaty loudspeaker whose height (45cm) is only slightly greater than its overall depth (41cm), and it weighs a persuasive 24kg (bend the knees). The driver complement is classic ATC: a six-inch Super Linear mid/bass allied to a one-inch S-Spec soft dome tweeter with dual suspension, both drivers made in house at the company’s Gloucestershire base. The sealed cabinet is pretty straightforward albeit featuring a distinctive extra layer of baffle on the front, which provides greater stiffness for the drive units and allows a carefully developed grille to be secured with an interference fit. The grille has vents cut in the frame beneath the fabric in order to provide a softer edge to the baffle and reduce diffraction.
A lot of the weight comes from the amplification and electronics pack on the back of the SCM20ASL’s cabinet. This comprises two Class AB MOSFET amplifiers, providing 200W for the woofer and 50W for the tweeter. That should be sufficient for most domestic requirements and then some. The electronic crossover is adjustable in input sensitivity between one and two volts and offers a bass shelf control, which acts to increase or decrease low frequency output and will help in situations where bass is too great (or small) for the room/tastes. ATC does point out however that boosting the signal is not beneficial to overall sound quality. Signal input is via an XLR socket only as is typically the case with ATCs and other active designs with studio origins. Finally, there is a power inlet – the amplifiers won’t run without juice.
Sound quality
ATC’s active speakers generally sound better with active preamplification, which is a problem for those of us that have a passive pre like my Townshend Allegri Reference. It can drive active speakers but they seem to improve in dynamic terms with a bit more oomph from the control device. On this occasion it occurred to me that the Bricasti M11 Classic DAC that I bought last year has the option of volume controlled output, so I hooked it straight up to the SCM20ASLs to find out if the pairing would work. In short, it does, in fact it works so well that I have had to reassess the Bricasti’s capabilities and find them to be greater than originally seemed the case.
Long balanced cables are not something I get much use out of so I don’t have anything particularly good. The default option is a studio cable from Van Damme that is usefully flexible and 3m long but a bit tonally savage (it’s called Tour Grade, which explains why a lot of live music sounds the way it does). The combination of Bricasti, Van Damme and SCM20ASLs has a raw, unvarnished honesty that is never less than gripping, with coherence that is off the scale. It feels pretty stark after more refined amps, speakers and cables but I couldn’t stop listening. There is a plethora of detail to enjoy and pretty much the best timing I have heard with digital in living memory (about two weeks, give or take). Directly connecting a DAC with such a good volume control to active speakers is like hot rodding the sound, revealing texture, timbre and tonal riches that are not usually apparent and serving them up with a degree of integrity that is rare.
The sound isn’t quite as open as the best standmount and amp combinations, but I doubt you could do better with a pairing at the £6.5k asking price of the SCM20ASLs. More importantly scale varies significantly with recordings as it should do; some manage to totally escape the boxes, most are limited to the space between them. But it’s the immediacy that makes these ATCs so engaging. The precision snare work on MYT’s Till Tomorrow is combined with studio effects, which undermine overall sound quality but makes the music no less exciting and fresh. Bill Frisell’s live cover of Shenandoah starts quietly before the band joins in with a swell that is rarely so well delivered. The active nature of the SCM20ASLs gives them dynamic range that passive speakers can only dream about. It also gives them control, and it’s this that makes good recordings come alive in the room and makes the sound so real.
I found that I could just about reach each speaker with a 1.5m pair of Townshend F1 Fractal interconnects (note to self, must get something more suitable) and this helped smooth out the aggressive tendencies found with the Van Damme, bringing out the charm of a piano trio and inspiring some rare air drumming in the process. The cable change did nothing to undermine the superb sense of immediacy that the SCM20ASLs can deliver – it’s what makes good recordings sound so vital and alive and keeps you coming back for more. These speakers are escape machines in the best way, they draw you in and reveal just how great music can be in a way that eludes so much of the competition. They are not ultra-refined, you can’t hear the bass player fart even if it’s a windy day, but you will be carried away from your troubles and cares. They deliver music therapy squared and that can only be a great thing.
Wanting to play vinyl, like you do, I hooked up the Allegri Reference and was not disappointed with the results; the superiority of the source compared to digital was enough to offset any loss of dynamic impetus. What hit me straight away was that the record sounded good almost from the first bar. Usually, it takes a side of vinyl before the needle warms up and delivers its best. Here it was clear that the Naia gets to the good stuff even when relatively cool. It was a hot day however so that might have played a part. Once again, I was forced to ask why so few speakers have this degree of coherence. I guess it’s because active operation avoids some significant barriers in this respect, not least phase accuracy, and that two-ways have a head start in this area too.
Conclusion
I have to say that the SCM20ASLs have nailed it for me. These apparently simple and relatively compact loudspeakers get to the parts that few others do and make the music so appealing that doom scrolling is no longer a thing. They may not have DSP electronics offering all manner of tweaks but this is very much in their favour. The SCM20ASLs are an all analogue, linear power supplied musical truth conduit that will have you glued to your music for years to come.
I would go so far as to say that they are a cure for audiophilia nervosa: you’re no longer thinking about how to make the system better but just wondering which album to play next. Upgrades to the signal path are however always audible so those who want more will be able to continue the quest. The ATC SCM20ASL is a speaker for all but the most incurable of tweakers.