ATC speakers / Monitors

[AlmaAtaKZ]

Here is my ATC SCM7III just measured at 85dB 1m, 5ms gating in-room.

To my inexperienced eye the response is just about OK, directivity could be smoother (it is a very sharp edged cabinet) and woofer distortion is way too high (tweeter OK but not much better than many).
This is below even my own diy efforts.

 

[dfuller]

Here is my ATC SCM7II just measured at 85dB 1m, 5ms gating in-room.

To my inexperienced eye the response is just about OK, directivity could be smoother (it is a very sharp edged cabinet) and woofer distortion is way too high (tweeter OK but not better).
This is below even my own diy efforts.

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The distortion measures seem extremely high compared to other ATC measurements I've seen that include distortion.

 

[AlmaAtaKZ]

Indeed
Just realised it is v3, not v2. It is the latest one, with the Atc tweeter. Measured without the grille.

 

[AlmaAtaKZ]

https://atc.audio/wp-content/uploads/2020/06/Hi-Fi_Critic_ATC_SCM7.pdf

 

[dfuller]

https://atc.audio/wp-content/uploads/2020/06/Hi-Fi_Critic_ATC_SCM7.pdf

This seems remarkably bad compared to the Stereophile measurements, which are closer to yours in terms of axial response.

ATC SCM7 v.3 loudspeaker Measurements | Stereophile.com

Sidebar 3: Measurements John Marks sent me the review pair of this elegant British, sealed-box minimonitor to run through my loudspeaker test regime. I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the ATC's frequency response in the farfield (I measured serial...

www.stereophile.com

 

[Ultrasonic]

@AlmaAtaKZ is that distortion without the time gating? I think it must be to go as low as it does? This wouid likely explain the higher than expected distortion shown I think.

 

[AlmaAtaKZ]

The distortion graph is from the same gated sweep. Double sweep with increased depth.

 

[goat76]

The distortion graph is from the same gated sweep. Double sweep with increased depth.

How far from the closest boundaries, like walls, floor, and ceiling, did you managed to place the loudspeaker for the measurements?

I have never managed to get a gated window of more than around 2-2.3 milliseconds in the room where I measure my loudspeakers. Are you sure the 5 ms window really gated out all early reflections from your measurements?

 

[AlmaAtaKZ]

1.2m

 

[Atc4ever]

It is interesting that the atc scm20 passive, from the beginning of the 90s (the first version) weighed 22.7 kg, while today's version of the same speaker weighs 18 kg. Obviously a lot has changed in 35 years.
Whan about the sound?

 

[goat76]

It is interesting that the atc scm20 passive, from the beginning of the 90s (the first version) weighed 22.7 kg, while today's version of the same speaker weighs 18 kg. Obviously a lot has changed in 35 years.
Whan about the sound?

According to ATC, the passive version of the SCM20 “has been in continuous production since 1990 and has evolved through four driver/crossover revisions into its current form”.

I can't answer your question about what might have changed in the sound over the years, as the pair of the SCM20s (latest revision) I have now is the only pair of 20s I have heard. But what I can say is that I‘m impressed with the sound of this loudspeaker; it sounds crystal clear, clean, precise, and is brutally revealing of the music source.

While both the SCM11s and the SCM40s also have a revealing, clean, and highly detailed sound, the SCM20 is a step up in the “clear department”. I don't know if that has to do with the “S-spec” tweeter and the “Super Linear” mid/bass driver found in the SCM20s, as the other two models already show a very low level of distortion in their measurements.

Maybe something will show up in the measurements I will do at some point, but at this moment, I just want to listen, adjust the speaker placement to perfection, and fine-tune the subwoofer's level and crossover point for a totally seamless integration with the main speakers.

 

[574stereo]

It is interesting that the atc scm20 passive, from the beginning of the 90s (the first version) weighed 22.7 kg, while today's version of the same speaker weighs 18 kg. Obviously a lot has changed in 35 years.
Whan about the sound?

Are you comparing active/passive?

The drivers have actually got slightly deeper over time… but only marginally… they’re otherwise very similar…

 

[Atc4ever]

Are you comparing active/passive?

The drivers have actually got slightly deeper over time… but only marginally… they’re otherwise very similar…

All passives

 

[goat76]

Here is my ATC SCM7III just measured at 85dB 1m, 5ms gating in-room.

To my inexperienced eye the response is just about OK, directivity could be smoother (it is a very sharp edged cabinet) and woofer distortion is way too high (tweeter OK but not much better).
This is below even my own diy efforts.

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I must say it’s really great that you share the measurements of your SCM7. This is likely the thread with most user provided measurements on this forum.

As already mentioned, the level of distortion seem to be somewhat high compared to other ATC speakers, but at the same time, this model is a tiny even compared to the already quite small SCM11, so a higher level of distortion is expected.

I think the frequency response looks alright. The loss of energy in the 3 to 5 kHz area of the on-axis response is likely compensated by a bit of a raise in that same area in the directivity responses. Just like other ATC loudspeakers, the response is good enough to be considered a neutral loudspeaker.

 

[thewas]

While both the SCM11s and the SCM40s also have a revealing, clean, and highly detailed sound, the SCM20 is a step up in the “clear department”. I don't know if that has to do with the “S-spec” tweeter and the “Super Linear” mid/bass driver found in the SCM20s, as the other two models already show a very low level of distortion in their measurements.

Personally I would be surprised if a midwoofer sounds 'cleaner' than the dedicated mid driver of the 40, especially at higher volumes, some comparative mulitone distortion measurements would be interesting. In my experience such differences usually rather originate in the different frequency responses on and off axis, also measurements at the listening position when switched at the same locations could be interesting, even some local 1dB differences can quite change the long term impressions. But if you don't listen loudly or plan to add a sub the 20 can make a fine alternative.

 

[Atc4ever]

According to ATC, the passive version of the SCM20 “has been in continuous production since 1990 and has evolved through four driver/crossover revisions into its current form”.

I can't answer your question about what might have changed in the sound over the years, as the pair of the SCM20s (latest revision) I have now is the only pair of 20s I have heard. But what I can say is that I‘m impressed with the sound of this loudspeaker; it sounds crystal clear, clean, precise, and is brutally revealing of the music source.

While both the SCM11s and the SCM40s also have a revealing, clean, and highly detailed sound, the SCM20 is a step up in the “clear department”. I don't know if that has to do with the “S-spec” tweeter and the “Super Linear” mid/bass driver found in the SCM20s, as the other two models already show a very low level of distortion in their measurements.

Maybe something will show up in the measurements I will do at some point, but at this moment, I just want to listen, adjust the speaker placement to perfection, and fine-tune the subwoofer's level and crossover point for a totally seamless integration with the main speakers.

First pic : crossover from scm20, first edition, 1990
Second pic...redesigned crossover, single wire terminals, before 1995
Third pic : bi-wire introduced, after 1995.
Last pic : specification of scm20, 1995, from atc brochure

 

[Atc4ever]

...specification from brochure is before SL introduction

 

[goat76]

Personally I would be surprised if a midwoofer sounds 'cleaner' than the dedicated mid driver of the 40, especially at higher volumes, some comparative mulitone distortion measurements would be interesting. In my experience such differences usually rather originate in the different frequency responses on and off axis, also measurements at the listening position when switched at the same locations could be interesting, even some local 1dB differences can quite change the long term impressions. But if you don't listen loudly or plan to add a sub the 20 can make a fine alternative.

As I mentioned, both the SCM11 and the SCM40 already have a really low level of distortion all the way to the lowest bass frequencies, so I don't expect the perceived higher clarity of the SCM20 to come from an even lower level of distortion than that. The reason could be any of the things you mention, but just based on my listening experience of all three models, the SCM20 seems to have a sharper, more distinct, more powerful delivery of the transient response, and that's why I think I perceive their sound to be a bit clearer than the other two. It's not like the SCM11 and SCM40 don't have a perceived great transient response, but they are really a step up in the SCM20, with a crystal sharp delivery.
I'm using the same two subwoofers with all the ATC speakers, so with some crossover adjustments, they reach equally low in the bass frequencies.

The only reasons for the above that I can think of may be the differences between the S-spec tweeter and the Super Linear bass driver. I really don't know if the technical differences translate to real-world sound differences, so please, take the information below with a pinch of salt, as it comes directly from ATC's own literature.



This is what ATC says about the differences between the standard tweeter and the S-spec version:

"The standard SH25-76 and its ultimate 'S' spec stablemate approach these engineering challenges in different but equally successful ways. The standard tweeter has a novel and lighter moving mass bracing component, while the 'S' spec driver has an exceptionally powerful motor assembly that, when combined with the optimally stiff and lightweight coil former, delivers vanishing low levels of odd harmonic distortion and a well controlled extended frequency response beyond the limit of human hearing."

Technology - ATC Loudspeakers

atc.audio

And here is what they say about the bass drivers that utilize the "Super Linear" technology:

"ATC’s super linear magnet development is to add rings of the SLMM to the magnet assembly pole and front plate adjacent to and concentric with the loudspeaker voice coil. The effect of the rings is to reduce 3rd harmonic distortion by between 10-15dB between 100Hz and 3KHz."

Super Linear Magnet Technology - ATC Loudspeakers

Since the invention of the moving coil loudspeaker, designers have been looking for ways of improving the sonic performance of loudspeaker systems. No Company has put more emphasis on this than ATC, and with the development of the Super Linear Magnetic System one of the longest standing...

atc.audio

And here is a more in-depth explanation of the "Super Linear" technology: https://atc.audio/wp-content/uploads/2014/10/ATC-CORP-BROCHURE-FINAL-10.pdf

 

[Pearljam5000]

I've read a lot of times that ATCs lack bass and have less output than speakers of the same size
Why is that?

 

[goat76]

I've read a lot of times that ATCs lack bass and have less output than speakers of the same size
Why is that?

ATC prioritizes the lowest possible level of distortion in all their loudspeaker designs, and lets the physics dictate the bass extension. Even with their bass-ported speakers, they never utilize the port for deeper bass extension, and rather use it to lower the level of distortion resonances even further. If you need deeper bass extension, you either buy larger ATC loudspeakers or add subwoofers to your system.

People tend to hear cleaner bass as less bass, as a higher level of distortion in the bass region tends to be perceived as a louder and deeper bass. That may be another reason why people think that ATC speakers are leaner in the bass.

I use subwoofers with all my ATC speakers, as I want a truly full-range sound. No small to medium-sized speakers can do that without a significant raise of distortion in the bass. I find people often contradict themselves when buying small loudspeakers with way too impressive bass extension, which they, on one hand, defend their decision by saying that the "human hearing isn’t that sensitive to distortion in the lower frequencies anyway", but right at the moment they add subwoofers, they immediately say that "using a low-pass filter is a must to achieve a cleaner sound".