Any Thoughts On These?


high-amp
I've done serious seat-time with the ML Motion 60 XTi in two different shops with, obviously, different listening rooms & acoustics.  Both listening rooms, however, were somewhat similar in dimensions.  Here's my take and please remember this is all, of course, IMHO:

First shop used a 60 watt NAD integrated amp whose model number I can't remember.  Room dimensions were something like 17' X 20' with 7' ceiling.  Kinda like a conventional living room with carpeting, bookcases, sheetrock construction, etc.  I think the NAD might have been a Class D design.  The ML sounded very nice but I don't think that NAD had enough power for them and I don't think it was the right match for 6 ohm nominal load speakers like that, even though those ML are relatively sensitive.  The money chair or sweet spot in that room was about 9' away from the ML.  The ML were about 6' apart and the wall behind the sweet spot was about 3 or 4 feet away.  This would make for around 2 or 3 feet behind the ML front baffles and wall behind them.  IMO, speakers with AMT tweeters need more room behind the sweet spot or listening position.  A friend and I both got significant listening fatigue after about 30 minutes or so of concert level volume and a little less.

Second shop used a Simaudio Moon NEO 340IX.  This is one outrageously and hellaciously nice amp!  The ML in this shop only had, we were told, about 40 hours play time on them.  Probably not enough but they still sounded really, really nice.  In fact, my friend and I thought they sounded a hair better than a pair of GoldenEar Ttriton 2+ we A/B'd them with.  However, to be fair, we were told those GE only had about 20 hours play time on them.  Probably not nearly enough.  The listening room was a little larger than the first one but chock full of other speakers & components behind the speakers we listened to.  It, too, was like a conventional living room.  The money seat was about 9' from the speakers but had about 12 to 14 feet to a wall behind the sweet spot.  The ML and GE were separated by about 6'.  The wall behind their front baffles was about 6' away but, again, just chock full of other speakers and components.  Not the greatest set-up but I believe these ML definitely benefitted from the space behind the sweet spot.  No listening fatigue at all after about an hour & a half to two hours at concert level volumes.  I was impressed by both speakers but definitely gave the nod to the ML.

My advice:  if your listening room doesn't have at least 6' (preferably more) of empty space behind the sweet spot, you might like something else, like Revel Performa3 F206.  That's what I bought after auditioning somewhere around 18 different pairs of speakers and they sound even better in my living room set-up than they did in the shop I bought them from.  I also liked the PSB Imagine T2 and the Monitor Audio Silver 500 but the Revel were just jaw-droppers!

Because of my experience with AMT tweeters (not my first, BTW-I demoed the old ESS AMT back in the day) I've always wondered if Beryllium tweeters might need similar room placement (i.e. lots of empty space behind the sweet spot).  Anybody have any experience with this?
Comparing the Motion 40s vs. Motion 60s, if you have a really good (fast & clean) subwoofer to go along with your system, try the 40s too. Remember, AMTs are super-duper-fast. Need a good fast sub to keep up.

With the smaller mid-woofers and smaller AMTs in the Motion 40s, they sound a bit more neutral and a tad less tubby on the bass using a mid-fi grade amplifier. If you step up like @knighttodd has running a higher current/quality amplifier to control the woofers, either ML40s or ML60s "can" sound even better. The room size/shape and speaker positioning matters too of course. Your situation may vary.

The Motion 40s are (92db sensitivity) and Motion 60s (94db sensitivity) and I did some testing with a small 10-watt triode tube amp for fun. While they sounded nice and smooth, good midrange, these Motion series speakers do appreciate a bit more power and control using a more capable amplifier (think big transformers in the amp) to perform their best.

Running standalone speakers only, I liked the Motion 60s only when paired with really good amplifier(s). Need not buy the Motion 60s (for 2ch audio) if you re only going to run a lower grade HT receiver, its a waste of money for the 60s. They deserve a lot more. With a great main stereo amplifier, and paired with a great subwoofer the midrange and mid-bass on the (lower model) Motion 40s also sounded really nice, neutral, nothing stood out too much. A few buddies preferred the Motion 40s in a smaller room setting too.

I did not get a chance to hear or try the Motion 60 speakers with a pair of really good 100wpc push-pull tube amplifiers. Tried the 40s with them though, and they sound great. I design and build my own AMT speakers for fun the past 3+ decades, and believe there is even more potential to the ML Motion 60s given a chance. Step up on the front-end, power amplifier(s), and the Motion 40 or 60s can sound very nice. Best of luck

@oldaudiophile btw, I worked at ESS early 1980s :)

oldaudiophile - decooney lots of good details, thanks. I do not have much room to pull speakers out from the back wall. I'm thinking I'd like to set them & forget them at around 12" or so. 

knighttodd - as both the guys above state, sounds like the sound improves the more power you give 'em.

A lot of people say speakers first then front end, I' starting to think the other way around at this point.