ATC SCM40

@jallan That’s pretty accurate overview ! I remember that GAS amp (I hate to say I’m that old) as at the time, they were excellent for the money. Ampzilla/son of was a great amp, more reliable than many others at the time. SAE was similarly reliable, but the GAS sounded better. Those were still the days of Phase Linear ($1 per watt) 400 amps!

People use that phrase "power hungry" and I get it, that phrase is often "situational" because I think this opinion comes from trying a low output amp (50W-75W?) that is often not as well designed as the higher power stand alone amps. Many of these demo experiments are with integrated amps or stand alone receiver company amps -not a high end design. The larger amps are usually ruled out due to cost, so usually not in play in a target system where people are searching for a bargain. Good example is a Crown D150- did not sound as good as the DC300. So sometimes it was companies just tried to make a cheaper amp that was lower power to fit the market, not just downscale the better higher power amp. (for background, it costs nearly the same to build a 75W or 150W amp vs a 300W one- the big costs are power supply, metal, meters, etc).

40s are optimized for low end extension vs efficiency, this is ATC’s preferred way of approaching loudspeaker design. Amps are cheap in this era so it’s not so difficult to get a larger 200W amp vs a 50W one. Much better place to invest $ is in the speaker with better low end and find a way to get a larger amp- even if not immediately. The big payoff is better low end AND much improved dynamics, which people don’t often think about until they are in their living room listening to "Fanfare for the Common Man" or Dark Side, or something that has some dynamics to it.  Dynamics plays such a significant role in realism.

Brad

@steve59  With all due respect,  I work with ATC so I am terribly biased in their favor, but I have worked in the speaker industry for 40 years with many different manufacturers including those with large engineering departments (such as JBL).  I have seen a lot and I know the OEM market a bit and how manufacturers make money there.  The ATC mid driver is not comparable to anything that I have seen on the market over the past 40 years and even today, it still stands alone.  The mechanical design and execution are beyond anything possible in OEM as it would be impossible to turn a profit on it.  No one would pay $1400 for one and put it in a speaker.  It has features that are not easily explained to a speaker owner as they are a physics and material science master class.  A far larger motor, a much greater stability in linearity due to two [dome] suspensions, lower distortion especially under higher dynamic ranges (115dB potential in the SCM150 to reproduce enormous peaks).  It is completely hand made to get the results the company owner wanted.  

You cannot build that driver on a machine and the techniques to build it are so nuanced that there is no copy available from anyone.  I would cost a bloody fortune to reverse engineer and you couldn't sell enough of them to make it worth it.  That's why there is no equal out there.  I agree there are a few 3 inch mid domes that look like the ATC from the outside.  But remove the driver and look at them vs the ATC side by side and there is no comparison between them-from a design and construction point of view.    And DSP cannot fix distortion inside the driver- once it's there, it's always there covering up details.  .

Brad

@soix

There are two versions of the mid driver, the "normal" one in the 40 and the pro 25 and pro 45. Then there is the "S" version (for super dome), which is in everything else (50 on up). I remember when I was first getting to know these parts and found out the recone kits for repairing both were exactly the same. The only difference between the two was a larger magnet (larger motor) for greater power - which relates to higher power handling and greater dynamic range. So from a technical point of view there is only one ATC mid dome, with a version that employs a larger magnet. Everything else about it - the coil, the gap, the frequency response etc- is identical. The two versions sound exactly the same, the "S" version in the 50 on up is just capable of more output, more SPL, which matters in some situations but not all.  

Brad

@viethluu -glad you own ATC, but if you consider having a wide dynamic capability "sucking power" I guess you could say that?  Most of them will play a good deal louder at lower distortion than other speakers of similar size (which is what makes them work in studios).  Also I am compelled to add its amps that have a "dampening factor", not speakers.  You are right that dampening factor is indeed an issue!  Dampening factor is best understood as how much "control" the amp has over the drivers, revealing itself on low frequency drivers in audible demos between a higher gauge cable vs a lower gauge one.  It's a pretty easy demo to do at home.  Compare the same length in two different gauge cables and you will likely hear the difference in tightness of bass.

About Class A.....you are right that it is suboptimal for moderate efficiency passive speakers unless you listen at low levels.  Class A doesn't quite have the appeal of Class AB anymore due to high heat at higher power output levels.  Its expensive, it runs hot and most of us don't want noisy ventilation fans on our amps in our living room.  Class A is not easy to design/build at high power levels (such as 100/ch)- so they are more likely to be found very low power outputs-  such as 5W to 25W per channel.  

Brad