ATC SM75-150S Dome Mid Measurement Data

Well, there do seem to be quite a few people on gearslutz (and elsewhere) who think the ATC mid is the best mid they have heard. And they are professionals who are listening critically for flaws, all day, day in & day out.

OTOH, there is less than a handful of amateur critics here (a couple of whom seem to take an almost perverse pleasure in "winding people up") whose exposure to ATC speakers is extremely limited, yet these people feel qualified to take ATC to task about some alleged problem with the midrange.




[P.S., begin your reply with "Nothing alleged about it bub....." and finish with a ]

 

Hey Bub, what can I say? The measurements tell the story.

And for what it is worth, if you have bought a new pair of ATC's in the past 18 months, their latest 16 ohm dome is very slightly different. It is slightly more efficient, displays slightly less distortion, but measures exactly the same in terms of amplitude.

Obviously that doesn't affect you as you have the older ones now don't you

 

In the first place, we have shown that you are measuring the wrong drive unit, and secondly how come it's you & BBV versus seemingly the rest of the world?

 

No Bub, we are measuring your drive unit. Unless of course you had the midrange domes changed in the past year or so?

And I repeat, the amplitude response (with it's irregularities) remains the same.

And sorry to say Bub but there are far more engineers who prefer to use an alternative, than there are those that rely on ATC's.

 

The unit is superb. But it does have a resonance in the upper band and IMO ATC would do better to Xover lower down, not only leaving out the resonance but improving vertical dispersion. Plenty of superb tweeters that can Xover around 2.5KHz.

 

There's no need to be sorry, Mike. I'm sorry that you appear to have become rather bitter & negative about everything. The OEM unit is not the same, being 8 Ohm, rather than 16. Check with the factory.

The issue isn't whether most studios are using ATCs, it's what the people who do use them think of them, Mike. No-one else seems to hear the distortion which you & BBV are claiming is present.

 

Tenson.

You should phone ATC, and let them know where they are going wrong with this driver.

 

Bub, we have checked with the factory - hence the detail of any slight differences and their dates in my previous post. I have given you the response. Your units are the same as the ones measured, and the latest varient is exactly the same in amplitude response - and hence peaky unless EQ'ed.

 

Mike, you haven't closed the logic loop of effect and cause.

But the bottom line is the assumption by you, Jek, Tenson et al that ATC do not know what they are doing. Whereas it is much more likely that they have good reasons for arranging their speakers as they do and not (for example) making Proac clones.

FWIW we don't even know the arrangement of the ATC crossover.

Paul

 

Paul,

We know that they use fourth order slopes at 380hz and 3.8khz. What we don't know is if they correct for the amplitude irregularities by employing EQ. It would be surprising if they didn't - given the rather uneven frequency response across the pass band.

 

I'd agree Fox - that's the point. That they are virtually identical. That the amplitude response IS identical.

 

The factory told you that 16 Ohms was the same as 8 Ohms? They must have known it was you, Mike.

FWIW, I spoke to Bob Polley on the phone, and asked him to bring my old speakers up to current spec last Easter (2007), while they were in for a service. I asked him about any available upgrades, and effectively gave him a free hand with my speakers, money no object.

But whether or not the Mid driver has changed in the last few months, is completely beside the point. The Gearslutz thread is from 2003 or 2004 (can't remember which).

The point is that two people here "spouting off", so to speak, are claiming they can hear distortion, whereas the rest of the world seemingly does not have that problem.

 

Bub, do you have any idea what difference a 16 ohm driver might make? Do you understand the term "amplitude response"? Genuine question because you still seem to be under the impression that your drive units would sound different whereas ATC themselves confirm that they really wouldn't.
I'm sure Bob would have let you know if he'd replaced the midrange domes - you would have noticed the shiney new dome as well - even when they are seven foot up in the air!

Bub, there's lots of people who think they sound wrong in some ways. At no point have a said they are a bad speaker - merely that they are flawed. As you listen so far off axis, you probably wouldn't hear small levels of 3rd harmonic emanating from the dome. Hey. Enjoy what you've got. Just please don't try to tell experienced listeners who don't get on with them that they are deluded. The measurements support our case to some degree.

 

Hold on - that's a bit of a sweeping statement. You started off with a fairly specific complaint about the upper midrange, but now it's morphed into "they sound wrong in some ways". Which ways? And who are the "lots of people"? It's all gone a bit vague.

You are an "experienced listener" are you? Do you listen critically to monitors for a living? What is the basis for your implied claim that you are an experienced listener?

And these measurements (of the wrong driver) are now only supporting your case to "some degree"? The wheels are coming off the wagon.

 

No we don't. We assume that's the case.

We know that if the measurements up thread are correct then they employ EQ.

Paul

 

No it states the crossover points in the review you linked to. We also know that they use 4th order slopes as it became common knowledge when they swapped.

Do you have good reason to doubt them?

 

Pro users employ atc to do a particular job - this job is not musical enjoyment. A fact you seem not to have grasped. Many of them have permanent threshold shift from motorhead gigs!!

There is no-one saying ATC don't know what they are doing. Its a very competent design. But all designs involve compromises and this is the compromise of the ATC - and one I find particularly tough to stomach.

My ex heard it and so did two others so that is good enough for me. People who seem to buy atcs also seem to buy mana, linn and naim which all offer similar colorations so I conclude they either cant hear the short comings or they find that coloration attractive.

 

Huff as much as you want Bub, I know you are one of the few people who never gives up - even when the evidence is staring you in the face.

 

Until he sells it and makes a complete about face

 

Well, if that's good enough for you, then game over. You, your ex, two others. A panel of experienced people who know their onions. And the professional users, like Sony Music for instance, have either been deafened by Motorhead gigs, or enjoy the coloration.