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[BOOM TOOLS] Speaker Test: ATC SCM50ASL Pro - 10 questions

boom library speaker test atc scm50 asl

BOOM Sound Designer Michael Schwendler has extensively tested some speakers for his new studio. Read on to see what was importand to him and why the "ATC SCM50ASL PRO" speaker won the race.

- 3-Way Active Speaker
- Frequency Response -6dB: 38Hz & 22kHz
- Weight: 48.9kg
- Price: 12.499,00€ / pair

1. Shortly describe the speakers, from which manufacturer they are and list the technical hardfacts.

It’s about the„SCM 50 ASL Pro“ speakers by ATC, a British manufacturer who is quite famous for his soft dome midrange driver, which was already built in the seventies and continually refined since then. The membrane of the chassis in the soft dome has been replaced by a fabric. Not too many manufacturers do that.

As technical hardfacts there are: a 25mm soft dome tweeter, a full “SL” spec 9˝/234mm bass driver and the ATC 75mm “Super Dome” mid driver. As well as an on board grounded source 350W Tri-amp pack, LF contour control and clip indication.

2. How many speakers did you test in which period of time before you came to a decision?

In total, I have dealt with six other speakers more closely:

1. Event Opal
2. Neumann KH 310
3. Focal SM9
4. ATC SCM 16
5. ATC SCM 25
6. PMC twotwo-6

Altogether, the tests extended over a period of about one month. Just as long as the take-back deadline of the retail store allowed it :-)

3. Explain your approach on the testing. What did you watch out for and what was of most importance to in your selection? Also compare directly with the products of the other manufacturers.

Actually, the ATC „SCM 50 ASL Pro“ attracted my attention rather accidentally… But let’s start at the beginning: basically, it was very important to me for the speakers to produce a good sound – pretty obvious. They should simply play back the pure sound content of the record.
Starting point of my search was the Event Opal with which I worked for about 3 years. At that time, I thought they were great because they had an amazing impulse behavior and reach down to 40 Hz. However, I always had the problem that with higher monitoring volume of low-frequency material there occurred quite obvious port sounds – the air in the reflex vents is moved too heavily here – and unfortunately, you heard that sound, even though I routed them through a subwoofer with bass management, it still was too serious. Furthermore, the Event Opal had an increased inherent noise. There was always a slight hiss and while monitoring recordings, that’s of course rather suboptimal. Thus an important argument for the purchase of new speakers was a low self-noise level. Due to a test report in a German audio journal my attention was drawn to the newly released Neumann “KH 310”. In contrast to the Event Opal, these speakers represent a three-way system and have a soft dome midrange driver. Since in my opinion the Event Opal are not quite prominent in the midrange, the Neumann were clearly preferable. The self-noise level is low as well (at least as long as one doesn’t wind up the input level) and it’s top quality. I was actually very satisfied, but then I accidentally stumbled into an audio retailer in Berlin and just wanted to compare their audio character to other speakers. So I listened to the „Focal SM9“, as well as to the smallest speakers of ATC from the Pro series, the „SCM 16A Pro“– in combination with the Neumann subwoofer “KH 18” (the “KH 310” speakers were running via the same subwoofer). The latter combination totally surprised me, especially because the “SCM 16A Pro” were the only two-way speakers among the test candidates and still played considerably better than the Neumann, which I had virtually bought by then – but still had the right of return for 30 days, which I then made use of. The Focal SM9 I thought were great, too, but the ATC simply were faster and more detailed.
After consultation with other audio retailers, I was advised to go for the bigger ATC “SCM 25A Pro” instead of the “SCM 16A Pro” (two-way system), an advice which I heeded and thus ordered. Unlike the Neumann, the ATC sounds way more natural and recordings simply seem more genuine, in my opinion. The Neumann speakers gave the sound a nasal, mid-tone character. Nonetheless, the “KH 310” are great speakers with which you can enjoy working, but in direct comparison I would always opt for the ATC. As a consequence, I returned the Neumann to the retailer.

With the ATC, my original budget was greatly exceeded so I decided to still check on cheaper alternatives. So I then tried the “twotwo-6” by PMC because they scored very well in diverse tests and I had read a lot about it on the internet. But in direct comparison, these speakers couldn’t match up to the ATCs, either. However, it was kind of an unfair comparison: firstly, the “twotwo-6” speakers are equipped with a two-way system and in terms of price they are similarly ranged. But still, these speakers are well-manufactured, tonally great equipment, too. But there’s one real catch: what disturbed me with the “twotwo-6” was the high self-noise level and since this was an absolute exclusion fact, they got returned very quickly to the retailer. The self-noise level was even much higher than with the “Event Opal”.

Did the ATC speaker “SCM 25A Pro” convince you straightaway? Or were there counterpoints, too?

Actually, I thought they were quite cool right from the beginning, but unfortunately, they cost twice as much as the Neumann speakers. There were even technical disadvantages: what I disliked about the “SCM 25A Pro” was that they have a ferrofluid*-cooled dome-tweeter. Regrettably, ferrofluids can dry up in the course of time, which ultimately leads to its malfunction. Furthermore, I thought the sound in the highs was a little sharp (especially in direct comparison with the PMC). Coincidentally, the retailer of my trust had some used ATC „SCM50A Pro“ at hand, the next larger version of these speakers, which I could finally claim mine at a small extra cost. These speakers have a different tweeter and woofer, other than the”SCM 25A Pro”, but the same midrange. I virtually bought them blind, but I regret nothing :-)
*Ferrofluids are used in speakers to conduct the heat away from the space between the voice coil and the undulator and to absorb the movement of the membranepassively. They’re located where there normally would be the air gap around the voice coil and are held by the field of the permanent magnet.(source: German Wikipedia)

4. How did you proceed with the speakers? What was your testing approach?

I did the A/B-monitoring which means listening with one channel out of phase to cancel the phantom center. By using a monitor controller I was able to switch straightly between the boxes. At a certain point, I brought in third parties. People who didn’t know much about this issue or who also didn’t have professional hearing abilities or who never had to devote particular attention to these details – and guess what: their feedback was really interesting and enriching to me!

5. Did you test all those speakers in your new studio?

No, I had all of them in my old room, except for the small ATCs and the Focal - I only tested those two in the store in Berlin.

6. In how far did the ATC SCM 50 ASL Pro change or improve your working method?

Not only do I have new speakers, but because of the relocation of our office, I also got to create and set up a new room which now is strongly acoustically optimized. You definitely have to get used to such an improvement first! ☺By now, I have the new speakers a little longer than three months and I’m getting accustomed to them more and more. Furthermore, the monitoring happens to be louder than before. Especially the perception of the treble is a different one now and so the mixing is less sharp. I also had to adapt my work process: it takes a little longer because you simply become fussy: you hear much more details which got drowned before. So in the end, you don’t necessarily work faster but that’s not the primary objective with this purchase.

7. For whom or which areas of application are these speakers suited for most likely, in your opinion?

The speakers - I have the active studio edition (SCM 50 ASL Pro) – are also available as passive HiFi version (SCM 50). This given fact shows the wide field of application. You can either listen to music, or monitor sounds with them – it all sounds just great! The speakers are simply awesome.

8. So what is your opinion on the price / performance ratio?

That’s comparable to the Trinnov MC Optimizer – everyone has to decide for him or herself. I bought the speakers based on the assumption that they should last until the end of my professional career. You must take into account that it costs valuable time to get used to new speakers. All these test runs and adaptations – they consume an enormous amount of time. Rather once invest properly, being sure you have a gorgeous, long-lasting product, and you’re done.
The “SCM 50” are being built for quite a long time, as far as I know starting in the nineteen-eighties. You can even send in 20 year old speakers and ATC repairs them. Pretty clear arguments for a long useful life, which is a natural course of action at these given costs. Furthermore, the speakers are continually being updated and new components developed which you can upgrade your system with. All components of the SCM 50 ASL Pro, except for the tweeter, are in-house productions of ATC. The great thing is that ATC now has produced their own new tweeter and someday, if I want to, it can be retrofitted to my speakers.

9. What’s your conclusion to the sound designers and BOOM blog readers out there?

One significant shortcoming: the price. But that’s something everyone has to decide for themselves. I fulfilled a small personal dream with these speakers and I enjoy working with them every day. In the end, it is also a question of taste, not only of budget. There are many excellent speakers which are excellently suitable to work with. It’s always a matter of how well you get used to your monitor, which is practically nothing else than a tool. If you know how to handle it, you will achieve exciting results. But let me say this: just as important as having gorgeous speakers is working under good accommodation conditions! ☺

10. How many points do you give the SCM 50 ASL Pro (0-10)?

As for me, it’s definitely worth 10 points!

Thanks, Michael

Here are some measurements Michael made with the new speakers:


This diagram shows the impulse at the listening position. All reflexions are below -20db, which is good.


This shows the frequency-dependent volume at the listening position with 6db octave smoothing. Very linear = awesome.


Here you can see the frequency-dependent reverberation time, in this case virtually linear to 20Hz at about 100 msec. Slightly increased at 35Hz and 20Hz, again: awesome!


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