ATC SM75-150S Dome Mid Measurement Data

Skye mastering uses them (100a's)...

The reason why you don't see ATC's in many mastering suites in the UK is that B&W have, in the past GIVEN these guys 800 series to use. Free and for nothing!!!!!!! It certainly happened at Polygram (a mastering engineer mate had his 801's changed to the Matrix version and was allowed the old ones on permanent home loan. Many years later they reside in his home theatre setup - he uses Harbeths for the little freelance monitoring work he currently does).

 

Because a) it doesnt affect the job b) many people cant hear it or dont care about it or actually like it c) all speakers have coloration and this one can easily be mentally subtracted during the work process. It just makes it irritating for long time listening for pleasure. Its not a pronounced character but it is there and becomes fatiguing over time. No speaker is perfect and on balance ATC is at the top of the heap for pro front desk work. Quite simple really.

B&W ugh... even worse than ATC.

 

I dont agree with much of that BBV.

a) it would affect the job (IF there are inconsistencies i the mid band its a crucial area)
b) I'm sure most people would be able to hear it (if it's there - I'm sitting on the fence). Whether they pay heed to it is another question
c) I agree with you on this one.

d).. ATC are used in a very small percentage of studio's. Very small. ''Top of the heap'' in quantity terms would be JBL, by a massive margin. ''Top of the heap'' in quality terms, well that's a matter of subjective view - but again in quantity terms, few of the worlds best mastering studio's use ATC. That's not a criticism of ATC speakers. I'm simply saying that in either the best mastering studios, or more typical recording studios ATC's are not very common.

 

I was being generous

No speaker is perfect - maybe the atc compromises suit the pro market as might be expected given their background? I suspect most people dont care or even dont notice it.

 

Bzz, I care and I don't notice it in my system (ie. dCS Player/DAC and ATC's) ever! So please count me in as one of the happy and contented ATC users.

 

I just downloaded ARTA and spent a few minutes plugging and fiddling. Using MLS and a microphone about 1m from the mid range of a single speaker just sitting there I get this.

I still don't understand why 'shin' used somebody elses measurements, if he's done them then posting is trivial.

Paul

 

Yes the data is predominantly of the 8ohm version. The only 16ohm measurements are the distortion and CSD plots.

However its worth understanding just what impact the Re of the voicecoil has on aspects of performance and particularly in relation to the measurements and the contentious points raised regarding useful driver bandwidth and associated crossover implementation.

All design aspects between 8 and 16ohm drivers are identical except the resistive nature of the VC. The mechanical driver parameters such as moving mass, resonance frequency, suspension compliance and all the rest are identical. So all important aspects such as those show at the beginning of this thread - ie. distortion, directivity, amplitude response and CSD will essentially be identical between units. This is further confirmed through the close correlation between data sets from myself and Ralph. Again if they weren't so close I'd have done a bit of extra leg work and prepared my own complete set of measurements. This topic was originally discussed over on DIYA - a place full of knowledgeable people - never once was the validity of the shown measurements brought into question because of Re. There's a good reason for that.

So there are no major operating differences between the 16 and 8ohm versions. They sound and perform identical. The reason ATC offer two versions is simply because of people who use passive networks and have amplifier considerations. 16ohm isn't better than 8ohm or vice versa when considering the driver in isolation such as the case here. But it could be important depending on the partnering drivers and equipment when considered as part of a system. However in this instance it has no bearing on the validity of the measurements nor does it impact in any way the points the both I and Mike have raised about usable driver bandwidth.

Before questioning something its important to, some extent, actually understand what it is your talking about otherwise confusion and myths can be formed. Just as is the case here and with some of the talk on gearslutz. That's not a condemnation but rather an observation and a friendly reminder to help move the conversation past irrelevant nit picking.

 

Well that plot doesn't look bad as I suspect the bass/mid wiggles are room reflections I suspect (?).

So many domestic speakers have a dip in the lower KHz crossover point which many here may prefer. Harbeth tend to have a 2db step down above 3K or so on many of their speakers - deliberately put there...

I get the impression that ATC's Billy Woodman is adamant he's doing the right thing and he obviously truly believes in his products. Like Naim, ATC only make changes when there's a big step forward and I for one can live with the designs as they are.

 

Time and effort was an issue. I'd taken the measurements prior to making a decision about sticking them on the internet. I hadn't saved the whole captured data set and only had the ARTA based measurements on disk, the WinMLS stuff such as FR etc. weren't saved at the time. To have repeated these measurements again would have meant time and effort because an accurate and repeatable test setup requires consistency as well as consideration of surrounding environment in which the measurements were taken, in otherwords hauling speakers, an amplifier and the PC based measuring setup outside. I saw little advantage to doing so because I understood that, for the data being shown, the differences were academic and since Ralph already had a near identical dataset we agreed the two could be combined in order to answer requests for some much needed objective data on this driver.

 

From that plot, I think the speakers are 1.2m out from the rear or side walls (or both). Could be wrong though

 

Ralph' plots, like my own, were taken in semi anechoic conditions ie. outside. For the wavelengths of the frequencies involved and the distance from the speaker/mic to nearest boundary(the floor) the measurements contain no reflections. An impulse response quickly and easily shows any problems in this regard.

What you see is the native driver response. We both can measure, with good accuracy, to at least 100hz using this setup.

 

It's not irrelevant nit picking. It's elementary science. Why did you throw your FR measurements away?

Anyway as a self-proclaimed expert rather than hand-waving can you document the change in moving mass and demonstrate that it's negligible? What about the rather large change in damping factor?

Paul

 

Paul,

Bob Polly has already confirmed that the amplitude response is the same. Given ATC's reliance on tight tolerances, it would be entirely expected for Shinobiwan's data to correlate with those provided by Ralph.

Your measurements sadly disguise the very issue we are talking about and are therefore of no use to the discussion. The resonance is just outside of the midrange dome's pass band.

For Bottleneck, the resonance is accepted by some. Just look at the TAD's. They have a similar resonance caused by the diaghram breaking up at 13khz - it's therefore advantageous to crossover at 7khz in order remove it's affects. These can be percieved as a hardening of the sound - an added zing. Once removed it's contribution is obvious even at such high frequencies. At two octaves below, the ear's sensitivity is considerably higher and therefore the affects even more intrusive.

 

Just one of those things. Had I known that I'd be using them on the internet at some point then yes, a more conscious effort would have been made to save them. As it happened at the time it was purely for my own benefit.

I have to ask you what does this have to do with the measurements shown and the points raised? I think I already know the answer to that but I'll bite anyway.

Damping factor, you'd better start talking about amplifiers in that case. Unless your using something very unsuitable and inadequate such as a flea powered SET then your point is absolutely mute and the driver performance whether objective or subjective is unchanged between the Re variants.

Changes in Mms to the extent where the physical properties of the driver are identical and the extra mass comes from a very slightly heavier voice coil then the only real and notable difference will be sensitivity, thats all you should care about outside of mating drivers, partnering amplifiers and passive network design.

Since we don't have complete data sets for the 8 and 16ohm ATC to compare then for illustration I'll use another driver from Scanspeak, the 18W sliced paper:

8ohm version:


16ohm version:


Driver to driver tolerances even between identical models could illustrate a similar fractional FR deviation.

I could go on with other examples to further reinforce this. As I've said a couple of times before, ATC's drivers are no different to the above example.

 

With any normal amp the dominant factor in damping is the voice coil resistance.

Paul

 

Where, and what exactly has he confirmed?

I thought it was interesting. Particularly idea to posting time.

Interestingly if you put the mic right in the face of the midrange dome then you get a 6dB/octave rolloff between 1250 and 2500Hz. The output then begins to plummet.

Paul

 

The vertical dispersion patterns of the tweeter and midrange dome do not promote listening on the bass unit's axis unless from around 30 metres Fox. They may well sound nicer positioned on scaffolding (and therefore I heartily condone the practice) but I would be most interested in measurements.

 

That the amplitude response is identical with all units, that the sensitivity is slightly higher with the S (which is common knowledge). I received an email from him yesterday. Send me your email address and I'll forward it to you if you still don't beleive it.

 

Yep,

Every single one of those installs will be EQ'ed by professional installation engineers. The easy way to know is to take an in room reading from the listening position. The last photo certainly looks like a PR stunt.

Have a look at the fantastic website for leading mastering house, Sterling Sound in New York.

Now note how the ATC mids in the third party loudspeakers are NOT two feet above the engineer. Also please note the absence of ATC monitors. Interesting given how much work they get.

 

Yes and exciting a resonance not only creates amplitude products at the resonance but also at orders of magnitude out from that point as well as increased distortion. The fact that its described as a resonance is telling that energy is being stored. Its a time smearing of the driver amplitude-time response in comparison to the optimal performance of the driver.

This stuff should be avoided regardless of any intent of the designer. Its gross distortion and arguably as objectionable as harmonic distortion(which the ATC's mids do very well considering the design specifics).