ATC SM75-150S Dome Mid Measurement Data

All in good time Joe.

Yes please.

 

Paul,

there only one CSD plot AFAIK. The "other" measurement is taken at very low level and only shows FR - hardly of much merit.

To be honest yes I could get another one measured but what's the point. You'll only refute the evidence till the ATC mafia are blue in the face. And I have better things to do.

As an aside, I mentioned the need for EQ andwas told ATC don't use EQ. The plots you posted suggested to Markus that they must use EQ. If they use EQ to attenuate the resonance then that would make sense as I suggested at the beginning of the thread.

 

If you mean that the crossover rollout at 3.5 - 3.8KHz is the eq then fair enough. I have no knowledge of further eq in addition to this on the active models.

 

Ralph's FR measurement at unspecified level shows the glitch. You are cherry picking your proxies to suit your prejudices...

And until you've seen this in an ATC implementation you haven't connected effect to cause.

Paul

 

I'm pointing out one set of measurements were taken in an abnormally favourable light for some reason. Are you suggesting that the others were deliberately taken in an unfavorable one?

 

We have no idea what level Ralph's measurements were taken at, it's not specified. It's also curious that the LDSG unbaffled response looks most like Ralph's whereas the LDSG baffled measurements look a lot smoother. I don't have much confidence in the relationship between these measurements and reality.

Anyway if this 'resonance' vanishes at 80dB in the mid range then that's more than loud enough for me to not care about it....

The point remains that if you're going to tie your subjective impression to this then you have to try a lot harder to demonstrate it. We'll leave your criticisms of the lack of foo-foo dust in the ATC internals for another time...

Paul

 

I can say it is a possible reason for the midrange criticisms indeed a probable cause of the hardness in my experience - but no more. If you want to dispute the evidence I really would lose the will to live if I had to provide you with more. Enjoy your purchase.

If you listen at levels below 80db I'm really surprised you haven't bought a graphic EQ yet though Paul. They just sound way wrong to my ears at levels below 85db - an opinion shared by two studio professionals I am friends with I should add. And that's 80db at 1m. How far away from them are you?

I don't think discrete components can be considered foo foo Paul but there you go. I'm sure the boards are perfectly suited to your requirements . I've wanted to try actively powering ATC's with decent electronics for some time, but now I'm playing with TAD's I'm unlikely to get round to it.

 

You haven't actually provided any evidence.

'My Cousin Vinnie' is playing at the moment. Average less than 70dBA on the meter. Normal TV levels. Not sounding 'way wrong' at all. YMMV of course.

A presumption that 'discrete' is better than integrated is 'foo foo'. See your anti-cable argument.

Paul

 

Have you seen the size of the heatsinks on, for example, a Krell KSA50mk2 50w Class A? They're big, infact a single side of the Krell(dedicated to one channel) has more dissipation area than the whole of the one ATC use to cool 3 channels. Take this question to the boffins on the solid state forum at DIYAudio and you'd get told in no uncertain terms that the ATC amps are, at best running several watts in class A and then the rest is AB.

This is no bad thing, afterall the ATC mid after EQ to smooth the response and, on the SCM50 baffle, a little baffle step correction at its very bottom end would do around 90dB with a single watt. Its a similar story for the tweeter but depending on the bass driver it could vary between about 85dB upto possibly the low 90's.

That's a lot of volume within those first few watts, especially for a domestic midfield setting. So whilst its definitely not 50w class A its not an issue either IMO.

BTW I've used the ATC myself and tried many different crossovers. Even when mimicking ATC's chosen slopes I wouldn't say the resonance is anything like objectionable. TBH you don't realise its there until you try moving the crossover away from it. I found I could make it sound even better when doing this, but I was using a different tweeter and the ATC SB75-234SC 9" bass driver rather the SL version that ATC use in their own monitors. The cabinet and baffle was also vastly different. The crossovers were different with me using digital FIR filtering and rather different topology. I choose sealed over ported bass as well. So there's many design differences that would mean the two loudspeaker systems weren't directly comparable despite sharing the same midrange.

 

We'll agree to disagree on that.

 

Two measurements confirm it. Look at Ralphs FR, the dip at ~4.5Khz is plain to see, this is the resonance. And again on my own CSD you can see the dip and then the resonance trail at exactly the same frequency. The FR tells you what the CSD will roughly look like given a bit of practise.




Not bad considering four drivers all showing the same behaviour, mine being 16ohm marked Jan 06 and Ralphs 8ohm units being much older(<1999) due to the linear profile waveguide on his. I've also had a pair of the standard version of the ATC dome mid and this showed the same behaviour so its clearly a physical design related issue.

I've had many of the more popular ATC drivers over the past few years. Only the ATC mid is really standout, their bass drivers are nice though. In case it isn't obvious, I like ATC drivers

ATC standard vs. super mid:



9" SB75-234SC:


15" SB100-375SC:


SCM-20SL (as used in the SCM20 monitors) The only one that disappointed me really:


I've also had a pair of their 9" PA range drivers but never really did anything with them so can't comment on performance.

 

Its funny your should mention that Mike. I always thought their drivers sounded really on form when driving them at realistic levels.

At low level listening in no way do they compare to level of detail and contrast dug up by the Audiotechnology drivers I'm using now but then again those don't sound as 'live' or dynamic as the ATC's when driven hard. Swings and roundabouts. Personally the ATC mid is still one of the best I've used and I've used a lot of well respected drivers.

 

That's been one of the unexpected pleasures of using the TAD drive units to be honest. I can listen at levels below 60db at the listening position and still get everything with the correct tonal balance. They don't change timbre all the way up to (And probably beyond) 110db either - quite remarkable IME and an unexpected bonus.

 

Hi SC,

I found this with the JBL S2 9860, but I saw this lack of change of tonality and timbre with change of output (volume) as a fault, since in reality the perceived tonality of music does change with loudness (volume). I put this 'fault' down to the pervasive colouration of the HF (horn) driver, which I mention in a previous post, and which you postulate as an effect of the horn (resonances).

 

I'd say thats more of a fault with the way our ears work.

 

Horn colouration is pretty easy to spot on an impedence plot, much like the resonance on the ATC plot. Horn colouration will show up as a series of wrinkles in the plot. The plot below does not suggest any colouration, and indeed Paul Messenger made a point of mentioning it's absence.




With regards to 2nd harmonic, please note two points with the attached. Firstly the distortion is raised 20db to show on the graph. Secondly the plot is taken at 100db, not the 80db used in the ATC plot. Even allowing for this, distortion never gets to accepted audible levels and at low levels would be to all intents and purposes non existant.



If you think that a speaker that sounds right at all levels is wrong, then you must think that a) the Quad ELS57 is horribly distorted, and that orchestras sound tinny when playing quiet interludes.

 

SM,
I see what you are saying, but my meaning regarding change in tonality with change in loudness was to do with absolute loudness, as in sitting nearer of further from a band/orchestra. I also take your point regarding the colouration I heared from the JBL's. If its not resonance of the horn, could my unease with the sound have been something to do with a (particular) aspect of the projection pattern of the horn, eg. reduced interaction with my room etc? I know, in theory, that reduction/elimination of a room's impact on the reproduced sound should be a 'good thing', but if that was the case we would all be listening in anechoic chambers?!

 

The acoustic impedance matching effect of the horn?

 

I assume that's the midrange driver? Passive crossover at 10k, your graphs show an issue at 10 and a bit? Strongly rising HF distortion? Ideal speakers for old people?

Paul

 

I just came back from public demo of the ATC SCM300 ASL in a big Hotel room (about 15-17 m x 13-15 m).

The presented system was:

Turntable SME Model 10 with the micro Benz LP cartridge
CD-player Naim CD555
Preamplifier ATC SCA 2
Speakers ATC SCM 300ASL

I was listening during the whole period of over five hours sitting in the sweet spot or near (1 chair away from it in different directions).
They allowed me to hear only one track (or not even) of one of my Cds so my considerations are concerning tracks of recordings I didn't know. They didn't want to play other material than theirs because they didn't want people to hear the system playing poorly due to "bad recordings".

In general the timbre was very good, the instruments didn't have any particular colouring. I could hear without any stress for the whole time, the image was stable and easy, even if I would consider it a little bit heavy.

The first LP I heard was from an album "Documenti del Barocco – Venezia". The track was for cembalo solo. The high frequencies were not (what I call) "free". I had the feeling that the cembalo was recorded in a small completely absorbed room. I thought it could be the adjustment in the phono preamp but through out the five hours that feeling remained more or less in me.
When the cembalo was playing louder then this feeling was much less. What I missed was the transparence, the airness, which I feel very important in a concert hall but with electronic music this is not necessary.

Hearing the next played record (Choral music from the Venice baroque) I could hear the male and female choir but I couldn't distinguish the separation between sopranos, tenors, bass and so on. The soundstage was very nice though.

Hearing electronic music with the first CD I liked how the speakers completely "disappeared" and the soundstage was a meter or two behind the speakers. The instruments were clearly positioned and were physical. The dynamic and punch were good. And I enjoyed the music.

Then back to a LP: Keith Jarrett, Live Paris.
The piano was "physically there". What was missing for my taste was the airness and freeness given by the high frequencies. I had also a strange problem with my perception: when the piano was playing the high notes its position seemed to move slightly to the right speaker. At a point I was doubting if the were three pianos on the stage. The soundstage was nice, big and stable.

The next LP was "Misty", Yamamoto Trio.
The piano sounded great but the drums fell completely in the background at the beginning. I hardly couldn't hear it. For the first time I was aware of a lack of (what I call) fine dynamic. When a few instruments were playing more or less at the same sound level, I could distinguish them so clearly. Also the gaps between the instruments were for my taste too loud. I started to have a feeling that some details are getting lost even if I don't know these recordings.

Then they played a track of a CD with a female voice. Oh yes, I forgot the name.
The awareness of the "loud" gaps between the instruments made me question if it is because of some resonances from the boxes. It didn't colour the sound though, or I was not much aware about a colouration or unnatural timbre.

The next LP was a part of "The rite of spring" from Strawinsky. Lorin Maazel recorded this piece with the Cleveland Symphony orchestra for Telarc. I have this recording on CD. It has a lot of dynamic with different wind instruments continuously coming above the orchestra. On this system this piece sounded terrible: Flat, hardly any dynamic, lack of transparency and narrow soundstage. In one word, Boaring! A big credit goes to the colour of the sound, which wasn't artificial. Well not completely: while the fortissimo of the timpani I had the feeling that maybe some resonances of the boxed were playing some trick on me. I could though hear well the position of the instruments.
Unfortunately for me parts of this Lp were played twice!


The sound of a track of the album Tutu (Miles Davis) was lacking of that freeness in the high frequencies but the soundstage was great.

Changing position (exactly in triangle) I could hear more punch and the sound had more presence. At the beginning it gave me the impression of the ah-ha- or wow- effect but the sound was a slightly too aggressive and hard for my taste. So after a while (one hour?) I changed place again.

It was a nice experience listening to this system and I'll try and get two personal demos for the SCM 150 and SCM100 (active) from the dealer, who is a very nice guy. In the personal demos I can then listen to my Cds.

I hope this is not too much OT for this thread but I didn't want to open a separate one.

regards