Hardware Reviews

ATC SCM40A: Unlocking the active speaker advantage

ATC SCM40A active speaker review https://the-ear.net

ATC SCM40A active loudspeakers

Active or powered loudspeakers seem to be gaining ground in the wireless world that so many music lovers choose. The sort of powered speakers that are making headway tend to be more about keeping costs down and features up, but that is changing; there are now some respectable speaker makers building wireless and sometimes genuinely active speakers for a market with limited space and a fear of cables. ATC have been making active loudspeakers for almost as long as they have been in business, which started in the seventies with drive units and progressed to full loudspeakers of the pro variety in the following decade. They are very strong in the studio world and have equipped facilities around the world with active systems large and very large but occasionally almost manageable.

Active speakers differ from the powered variant that is gaining in popularity by virtue of having an electronic crossover onboard and a dedicated power amplifier connected directly to each drive unit. Powered speakers by contrast usually have an amplifier in one cabinet that drives speakers which are effectively passive, inasmuch as they have a crossover between amp and drive unit. This means that they are much less expensive to build and thus more affordable to buy, but they don’t offer the degree of control that you get when there is nothing between an amplifier and a drive unit except a short length of cable.

ATC SCM40A active speaker review https://the-ear.net

We looked at the passive version of the ATC SCM40A, the SCM40 a few years ago and got an excellent result but have always been intrigued by the possibilities of the active alternative, which is the smallest three-way design in ATC’s catalogue. But small is a relative term. The SCM40A is nearly a metre tall and weighs a respectable 36 kilos, which is only 5kg more than the passive version, so the electronics add something, but this is a solid loudspeaker from the ground up. This mass comes down to the “massive, optimised motor assemblies” that control ATC’s drive units; we are talking magnet assemblies here. Where other brands use the smallest magnets that will do the job, ATC over specify the motor systems of their drivers so that they can endure the rigours of high power usage over long periods of time. It’s a pro thing really but reassuring for the domestic user because it ensures reliability in the long term.

Direct connect

The SCM40A’s drivers are all made in house and start with a soft dome tweeter with dual suspension in a precise alloy waveguide forming part of the mounting plate that you can see around it. The midrange is also a dome, a 75mm example of the breed, and the bass unit is a 164mm design with a short coil in a long magnetic gap for maximum control. Each driver has its own amplifier; the tweeter gets 32W, the midrange 60W and the bass unit 150W for a total of 242 Class AB watts per loudspeaker. The advantage that having an amplifier connected directly to the drive unit brings is far greater control of that drive unit’s behaviour. By giving each driver its own dedicated amplifier ATC can allocate power precisely where it’s needed and, critically, design the electronics and loudspeaker as one.

When engineers develop passive loudspeakers, they cannot know which amplifiers end users are going to be connecting, so have to make a speaker that should work with a wide range of amps. This combined with the resistive nature of crossovers means that passive designs are compromised in ways that active examples are not. That’s not to say that passive speakers are inherently flawed, but that active operation such as that found in the SCM40A confers an instant advantage. The approach is of course equally reliant on quality of amplification, and the inability to upgrade amps in active models is what stands in their way at least from a commercial perspective. But the fact that only a few professional studios use passive monitors says a lot.

ATC SCM40A active speaker review https://the-ear.net

Connecting up the SCM40As requires a suitably long pair of interconnects with XLR plugs. You could use RCA terminated cables with adaptors but that is a slight compromise. It’s also necessary to have an active preamplifier to drive them with. I discovered as much when using my Townshend Allegri Reference passive preamp with ATC SCM100SE active speakers a few years back; passive doesn’t cut it with these speakers. And while most preamplifiers are active, and a lot of today’s streamers incorporate a volume controlled output, this is a revealing speaker, so don’t expect it to make great sound with compromised ancillaries.

Sound quality

When I had the Naim 300 series electronics in for review recently, James at Tom Tom Audio asked if I could write about using the NSS 333 streamer and NAC 332 preamplifier with SCM40As as this is a combination he particularly likes. It didn’t take long to find out why. It’s a very entertaining and revealing combination that is also notably less expensive than using NAP 350 monoblock power amps with a pair of suitably capable loudspeakers. The Naim/ATC pairing delivers power, control and dynamics that do justice to the most intense recordings, whether they be studio creations like the Mahavishnu Orchestra’s Birds of Fire or Ryan Adams and the Cardinals playing live. If you want to hear what a kick drum is supposed to sound like, try this pairing and feel the speed and shape that well recorded examples can deliver.

But it’s not just about energy, this system delivered impressive transparency and a degree of phase coherence that is rarely encountered. This was particularly clear on Laurie Anderson’s Gravity’s Angel (Mister Heartbreak) where the singer’s voice and that of Peter Gabriel are combined in an unusually strong three dimensional fashion, each with its own distinct acoustic envelope. With tracks like this the speakers disappear and leave a living, breathing acoustic event in front of you. I have played this tune many times before but don’t think that it has ever been rendered with such strong imaging and vitality. It’s like sculpted sound.

ATC SCM40A active speaker review https://the-ear.net

With the rather more conventionally albeit expertly captured solo piano of Keith Jarrett on Testament, the SCM40As deliver a degree of solidity and presence that puts the performance right in front of you. You can feel just how stiff the wood and iron of the piano is; it’s like a living thing in the room, slightly hard edged but utterly convincing. This is a great recording no doubt, but you don’t usually get to hear it sound so vivid and real. Initial listening to the Naim/ATC combo was done with a fairly basic Van Damme microphone cable between NAC 332 and SCM40A, but James sent down some Chord Shawline X Aray cables to try. These brightened the balance to the extent that the angle of the speakers needed adjusting but delivered a more engaging and better defined result. Now the bass had even more power and precision with Sunson (Tripping with Nils Frahm) revealing its pulsing radiance extremely well, the deep controlled bass perfectly in phase with mid and treble.


One thing that struck me when reviewing the SCM40As was just how limp regular amp speaker pairings sounded when switching back to them in the system. It seemed as if something was genuinely amiss and I checked all the connections to make sure they were the correct polarity, and that the internal volume control on the streamer hadn’t kicked in. But no, energy levels had dropped, and it was largely because there were crossovers between amp and driver. I didn’t have a 250W amp either and that is a factor, but not one that usually sounds this obvious.

ATC SCM40A active speaker review https://the-ear.net

I tried a different preamp with the SCM40A in the form of a Chord Ultima Pre 3 to see what that would bring to the party. This was a tighter, more controlled even gripped and sorted presentation, that made it very clear when the right tweaks were applied to filtering on the streamer. The result being very low noise levels, precise timing and remarkable depth of image, with a Chasing the Dragon piece revealing its charm and beauty amid full scale imaging, while the prog-esque rumblings of The God in Hackney’s A Frozen Western were delivered with crystal clarity and produced depth perspectives that rarely appear.


The ATC SCM40A is a lot of loudspeaker and electronics for the money. The price might look high for a speaker alone but when you consider that each offers a combined power of close to 250W from three separate amplifiers, then add in the electronic crossover, it’s clear that on the value front they have plenty to offer. But it’s what they can do for your music that’s more interesting. If you want to hear right into every track, to feel the bass and enjoy real depth of three dimensional image, this is a very hard act to beat. The SCM40As make a very strong case for active loudspeakers indeed. They may require a couple of wires but that’s a small price to pay for home entertainment of this calibre. Audition at your own risk, your regular system might well sound a bit inhibited in comparison.


Type: active reflex loaded loudspeakers
Amplifier power: 242W Class A/B
Drive units:
Bass: ATC 164mm short coil bass driver
Midrange: 75mm ATC Soft Dome mid-range driver.
Tweeter: dual suspension 25mm soft dome
Crossover frequencies: 380Hz & 3.5kHz
Frequency response: 48Hz – 22kHz (-6dB)
Wired connections: XLR
Wireless inputs: none
Dimensions HxWxD: 980 x 370 x 344mm inc plinth
Weight: 36kg
Finishes: cherry, black ash, satin black, satin white
Warranty: 6 years

Price when tested:
Manufacturer Details:

Loudspeaker Technology Ltd
T +44 (0)1285 760561


active loudspeakers


Jason Kennedy

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