There's always plenty of heated debate regarding ATC's dome mid so I finally decided to put together measurement data and post it here to perhaps remove some of the subjectivity and also the bashing for the sake of bashing.
I should also thank Ralph who's FR, impedance data and accompanying notes/comments I have borrowed(excellent work Ralph!). Ralphs measurements followed my own very closely so thats reasurring regarding accuracy, it also saves me much time capturing, editing, converting and uploading that data.
Just a couple of very quick notes:
The distortion test was performed outside and at 90dB average measured at the mic which was exactly 2m from the driver. The driver itself was mounted in a Perceive Satallite enclosure with no crossover in place for both distortion and CSD tests.
Cumulative Spectral Decay and distortion measurements were taken in ARTA and STEPS software(v1.1.0) using a Behringer ECM8000 mic, both ARTA and STEPS were calibrated using a true RMS DMM, the mic sensitivity was taken as per manufacturer specs.
On Axis:
The amplitude response is not as smooth or as flat as might be expected for driver that costs so much or is held in such reverence. However the phase response is remarkably smooth between 300Hz-4kHz. The above plot is a 'nearfield' LF response merged at 700Hz with a 'farfield' high frequency response taken at 0.5m. The first major breakup occurs at about 4.5kHz and is also evident in the impedance plot below. Below 1kHz the response rolls off smoothly.
As mentioned, in order to use this driver in a system requires considerable EQ. This isn't easily achieved with a passive crossover, and the driver benefits from an active implementation.
Off-axis:
The off-axis response is where the driver really shines. It's easy to eqalise a driver to be flat on axis, but not so easy to equalise it for a flat power response as well. Only a driver with a consistent power response can be equalised to achieve both.
Below is an example of the ATC's consistent off-axis performance. EQ has been applied to flatten the response somewhat, and the consistency in amplitude response as the measurement microphone is moved off-axis is easily seen; at 45 degrees the amplitude response remains within +/-1dB between 400Hz and 2kHz. Only above 2kHz does the driver start to beam and the power response fall away consistent with size of the driver's diaphragm.
Note that the vertical scale is 1dB/division. By augmenting the ATC mid with a controlled directivity HF driver, a smooth roll off in the system power response can be achieved. By 4.5kHz things are getting nasty, so to use the driver up to around 3.5kHz as is found in ATC's own speaker systems suggests quite steep crossover filters are needed.
Impedance of 8ohm version
The impedance plot is well behaved with just a small glitch at 700Hz and a larger one at 4.5kHz. The driver resonates at 320Hz which is only marginally outside the claimed operating range of 380Hz to 3.5kHz. Normally a midrange driver is not used close to it's resonance frequency. But in the case of the ATC mid, it works very well down low, sounding better crossed around 300-400Hz than higher up. Of course, when used below 400Hz, a steep filter is recommended or power needs to be limited not exceed Xmax.
Distortion:
CSD:
Hope that helps demystify the fog of hype/BS that surrounds this driver. Make of the measurements what you will and please note the test conditions - it makes all the difference.
If anyone is interested in other measurements/conditions I'll should be able to provide them given time.
There also seems to be a distinct lack of measurements for the Scan R2904 ring radiator, if anyone wants those I do have them.
I should also thank Ralph who's FR, impedance data and accompanying notes/comments I have borrowed(excellent work Ralph!). Ralphs measurements followed my own very closely so thats reasurring regarding accuracy, it also saves me much time capturing, editing, converting and uploading that data.
Just a couple of very quick notes:
The distortion test was performed outside and at 90dB average measured at the mic which was exactly 2m from the driver. The driver itself was mounted in a Perceive Satallite enclosure with no crossover in place for both distortion and CSD tests.
Cumulative Spectral Decay and distortion measurements were taken in ARTA and STEPS software(v1.1.0) using a Behringer ECM8000 mic, both ARTA and STEPS were calibrated using a true RMS DMM, the mic sensitivity was taken as per manufacturer specs.
On Axis:
An externally hosted image should be here but it was not working when we last tested it.
The amplitude response is not as smooth or as flat as might be expected for driver that costs so much or is held in such reverence. However the phase response is remarkably smooth between 300Hz-4kHz. The above plot is a 'nearfield' LF response merged at 700Hz with a 'farfield' high frequency response taken at 0.5m. The first major breakup occurs at about 4.5kHz and is also evident in the impedance plot below. Below 1kHz the response rolls off smoothly.
As mentioned, in order to use this driver in a system requires considerable EQ. This isn't easily achieved with a passive crossover, and the driver benefits from an active implementation.
Off-axis:
An externally hosted image should be here but it was not working when we last tested it.
The off-axis response is where the driver really shines. It's easy to eqalise a driver to be flat on axis, but not so easy to equalise it for a flat power response as well. Only a driver with a consistent power response can be equalised to achieve both.
Below is an example of the ATC's consistent off-axis performance. EQ has been applied to flatten the response somewhat, and the consistency in amplitude response as the measurement microphone is moved off-axis is easily seen; at 45 degrees the amplitude response remains within +/-1dB between 400Hz and 2kHz. Only above 2kHz does the driver start to beam and the power response fall away consistent with size of the driver's diaphragm.
Note that the vertical scale is 1dB/division. By augmenting the ATC mid with a controlled directivity HF driver, a smooth roll off in the system power response can be achieved. By 4.5kHz things are getting nasty, so to use the driver up to around 3.5kHz as is found in ATC's own speaker systems suggests quite steep crossover filters are needed.
Impedance of 8ohm version
An externally hosted image should be here but it was not working when we last tested it.
The impedance plot is well behaved with just a small glitch at 700Hz and a larger one at 4.5kHz. The driver resonates at 320Hz which is only marginally outside the claimed operating range of 380Hz to 3.5kHz. Normally a midrange driver is not used close to it's resonance frequency. But in the case of the ATC mid, it works very well down low, sounding better crossed around 300-400Hz than higher up. Of course, when used below 400Hz, a steep filter is recommended or power needs to be limited not exceed Xmax.
Distortion:
An externally hosted image should be here but it was not working when we last tested it.
CSD:
An externally hosted image should be here but it was not working when we last tested it.
Hope that helps demystify the fog of hype/BS that surrounds this driver. Make of the measurements what you will and please note the test conditions - it makes all the difference.
If anyone is interested in other measurements/conditions I'll should be able to provide them given time.
There also seems to be a distinct lack of measurements for the Scan R2904 ring radiator, if anyone wants those I do have them.
Hi Shin,
Thanks for your informative post. It's always very interesting reading about "high-end" products.
How does this thing manage such low non-linear distortion?
Even down to 100Hz, at 90dB/2m (96dB/1m) this thing manages 0.3% THD?
That can't be right. That's actually better than most 8" bass drivers, and competitive with the tens...
Thanks for your informative post. It's always very interesting reading about "high-end" products.
How does this thing manage such low non-linear distortion?
Even down to 100Hz, at 90dB/2m (96dB/1m) this thing manages 0.3% THD?
That can't be right. That's actually better than most 8" bass drivers, and competitive with the tens...
tktran303 said:Hi Shin,
Thanks for your informative post. It's always very interesting reading about "high-end" products.
How does this thing manage such low non-linear distortion?
Even down to 100Hz, at 90dB/2m (96dB/1m) this thing manages 0.3% THD?
That can't be right. That's actually better than most 8" bass drivers, and competitive with the tens...
It might actually help if I'd uploaded the correct file
An externally hosted image should be here but it was not working when we last tested it.
There's always plenty of heated debate regarding ATC's dome mid
Can you elaborate? I don't ever recall reading where people
didn't like this driver. The ATC dome midrange is probably
the only real good dome midrange on the market, the rest don't
compare.
As mentioned, in order to use this driver in a system requires considerable EQ. This isn't easily achieved with a passive crossover, and the driver benefits from an active implementation.
I think you can say the same for many other drivers, lol....
The off-axis response is where the driver really shines.
You didn't need measurements to know that dome midranges
are sweet in this regard. Their drawback is the inability to perform
at a lower crossover point that a good midrange or midwoofer
can do. Data suggested long ago that this driver is best with
a > 500hz crossover point, perhaps ~700hz, the 300hz range is
far too low if you want to get any SPL. The steep slope recommendation will help alot and should be implemented
if you cross low.
The ATC is on my 'unique driver list' good for certain types of
designs
Can you elaborate? I don't ever recall reading where people
didn't like this driver. The ATC dome midrange is probably
the only real good dome midrange on the market, the rest don't
compare.
As mentioned, in order to use this driver in a system requires considerable EQ. This isn't easily achieved with a passive crossover, and the driver benefits from an active implementation.
I think you can say the same for many other drivers, lol....
The off-axis response is where the driver really shines.
You didn't need measurements to know that dome midranges
are sweet in this regard. Their drawback is the inability to perform
at a lower crossover point that a good midrange or midwoofer
can do. Data suggested long ago that this driver is best with
a > 500hz crossover point, perhaps ~700hz, the 300hz range is
far too low if you want to get any SPL. The steep slope recommendation will help alot and should be implemented
if you cross low.
The ATC is on my 'unique driver list' good for certain types of
designs
BlackCatSound said:
pinkmouse said:
Well, Shin has both, so he can tell us!
Its very easy to get the implementation of the ATC wrong, I even believe that ATC aren't completly on the ball here and its their own driver.
Without being armed with the measurements this driver is almost impossible to maximise the performance of. So not sure what or blackcatsound implementation was I can't comment, like I said the driver has problems which need to be avoided and address.
Its obvious weak spots are distortion low down, nasty resonances up high and a crooked FR. The strengths are good CSD and distortion in the optimium operating ranges, excellent off axis response lending well to good power response and excellent impulse response. There's also the subjective side where dynamics, transparency and great tonal realism show through, of course this is only once its been correctly implemented into a loudspeaker system with well matched drivers.
Re: Re: ATC SM75-150S Dome Mid Measurement Data
I originally posted this on a UK forum where there's an anti-everything that's well regarded faction. I wanted to provide and alternative to the subjectivity and actually provide measurements.
Since I copied and pasted that, it ended up here without actually meaning anything because we all tend to be more grown up about such things. Sorry for the confusion.
Those comments were made by Ralph but echo my own thoughts and I'd completely agree. So I posted them. The main interest is the measurements rather than the text.
One thing I realised when I posted these measurements was that they are far from perfect, in actual fact they aren't exactly stella considering the £390 each asking price for the drivers. TBH measurements are very important but so is the sound and the ATC's have an undeniable character that tradition cone mids don't have, if you've heard horn setups they're like that but without the distortions some of those present. Very powerful live sound rather than soft and polite, more true to a real performance IMO.
thylantyr said:
I originally posted this on a UK forum where there's an anti-everything that's well regarded faction. I wanted to provide and alternative to the subjectivity and actually provide measurements.
Since I copied and pasted that, it ended up here without actually meaning anything because we all tend to be more grown up about such things. Sorry for the confusion.
As mentioned, in order to use this driver in a system requires considerable EQ. This isn't easily achieved with a passive crossover, and the driver benefits from an active implementation.
I think you can say the same for many other drivers, lol....
The off-axis response is where the driver really shines.
You didn't need measurements to know that dome midranges
are sweet in this regard. Their drawback is the inability to perform
at a lower crossover point that a good midrange or midwoofer
can do. Data suggested long ago that this driver is best with
a > 500hz crossover point, perhaps ~700hz, the 300hz range is
far too low if you want to get any SPL. The steep slope recommendation will help alot and should be implemented
if you cross low.
The ATC is on my 'unique driver list' good for certain types of
designs
Those comments were made by Ralph but echo my own thoughts and I'd completely agree. So I posted them. The main interest is the measurements rather than the text.
One thing I realised when I posted these measurements was that they are far from perfect, in actual fact they aren't exactly stella considering the £390 each asking price for the drivers. TBH measurements are very important but so is the sound and the ATC's have an undeniable character that tradition cone mids don't have, if you've heard horn setups they're like that but without the distortions some of those present. Very powerful live sound rather than soft and polite, more true to a real performance IMO.
couple of questions...
Shin,
I noticed in your "perceive" thread you started with the regular 150 and then traded up to the 150S. Can you comment a bit on what you observed between the two models of the ATC mid dome...
Also, I am curious about some comments that have been made about the dome sounding better when crossed lower even though distortion clearly skyrockets as you go from 400hz down to 300 hz. I remember someone posting in another forum that they thought the real magic of full range drivers was the smooth run from around 200hz to 4000hz. I find it interesting that the ATC comes pretty darn close to running that range, but wondering why some find it just sounds better as things go even lower.
I have noticed that when a manufacturer cranks up the magnet/sensitivity on a given model the frequency response often gets a bit more ragged, do you find that to be the case here?
And finally, what makes me even more curious about the best lower crosover point for the ATC is that response seems to also drop pretty sharply below 400hz which I would think, when combined with the distortion issue would make for a crossover point around 450hz much more desireable than one around 350hz.
Anyways, I guess the bottom line is that for those of us thinking about this driver, and not having any reason to believe we will be lucky enough to run into a great deal to trade up, is the "Special" version worth the extra dough in your opinion. As listed on the Solen site, it is approximately a 45% mark up from the standard version.
Shin,
I noticed in your "perceive" thread you started with the regular 150 and then traded up to the 150S. Can you comment a bit on what you observed between the two models of the ATC mid dome...
Also, I am curious about some comments that have been made about the dome sounding better when crossed lower even though distortion clearly skyrockets as you go from 400hz down to 300 hz. I remember someone posting in another forum that they thought the real magic of full range drivers was the smooth run from around 200hz to 4000hz. I find it interesting that the ATC comes pretty darn close to running that range, but wondering why some find it just sounds better as things go even lower.
I have noticed that when a manufacturer cranks up the magnet/sensitivity on a given model the frequency response often gets a bit more ragged, do you find that to be the case here?
And finally, what makes me even more curious about the best lower crosover point for the ATC is that response seems to also drop pretty sharply below 400hz which I would think, when combined with the distortion issue would make for a crossover point around 450hz much more desireable than one around 350hz.
Anyways, I guess the bottom line is that for those of us thinking about this driver, and not having any reason to believe we will be lucky enough to run into a great deal to trade up, is the "Special" version worth the extra dough in your opinion. As listed on the Solen site, it is approximately a 45% mark up from the standard version.
I don't know what others regard as smooth but a driver that is within +- 1 dB from 500 Hz up to 4 kHz IS smooth IMO.
There are neither drivers that are perfect by themselves nor are there perfect crossovers - it is the combination of suitable drivers with accordingly designed crossovers and cabinets that give good results.
I have heard the ATC SCM 100 active (using this dome mid) lately. And I'd have to say it sounded astounding. The same accounts for the larges studio monitor by PMC that uses the same dome mid.
Regards
Charles
phase_accurate said:
Just to be clear, the quoted text from my post is actually Ralfs commentary that I borrowed from his website.
I'm sure your aware that I used and loved the SM75-150S. So your preaching to the converted here. Still the best mid I've heard
BTW I believe PMC no longer use the ATC and have instead developed their own variant for use in their best monitors. The mid range stuff still uses the Vifa D75 by the looks of things - an average dome mid at best compared to the ATC.
tktran303 said:
Irwin AR said:
Fixed:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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