This is primarily a nearfield monitor but can also be used as a midfield, with an unusual but rather attractive (imho) metallic burgandy colour scheme that really makes them stand out. Trust me when I say they look far far better in person than they do in photographs. The waveguide is also rather unique looking, having the tweeter recessed quite deep. This has a nice advantage of minimising the chance of accidental damage, as well as reducing buildup of dust.
But looks are one thing, sound is another, and these monitors deliver some seriously impressive sound. I found jumping from the Dynaudios to the PSI was a very significant leap up in sound quality in all areas.
The soundstage on the PSI is very precise and linear between the speakers (which disappear as point sources) thanks to its analog all-pass filter compensated phase correction and one of the tightest time aligned step-response between woofer and tweeter of any 2-way monitor in the world. Some people may find the soundstage a little too between the speakers and prefer more outer oval width and depth, but I actually feel that what the A21-M's offer here is a soundstage that'll translate better to more systems. Whereas some monitors have a huge soundstage but panning feels like jumping from a larger central area suddenly to the sides, with the A21-M I can hear better panning placement in between the center and edges. As for the sweet spot, its huge. Moving my head around I don't notice any significant shifts in response.
The overall dynamic response, freq response and tone is quite frankly glorious. Great extension to the lows and smooth and precise all the way up to the highest frequencies. My ears tend to be overly sensitive to metal tweeters finding them rather harsh, but these soft domes on the A21-M are wonderfully airy and detailed giving lots of information but without ever being fatiguing. Transient edges in particular really sparkle. There is no HF eq adjustment on these monitors, but frankly they just don't need it.
Don't think for one second this means it flatters the top end though,for one of the strongest assets of the A21-M is how ruthless they are at revealing distortion issues. Any kind of mp3 compression,nasty clipping or hard limiting in particular really sticks out at you. Be warned, some tracks you enjoyed before you may struggle to enjoy again listening on these, but thats kind of the whole point of monitors like these, to reveal the source warts & all and force you to work harder in creating a good mix.
Only the very finest mixes will sound good here and when you put on a track like say Dave Matthews Band - Let You Down or Massive Attack - Angel, it'll put a huge smile on your face.
Bass detail is surprisingly good for a front bass reflex port design, with no noticeable port chuffing issues of any kind at all!. Seperation of the different bass instruments that'll give sealed cabinets a run for their money. The power handling is also truly excellent, you can crank the volume up on these and everything stays relatively intact, with no compression artifacts or boxiness occuring. Your ears will mostly likely give out before the limiter lights come on.
Crossover-wise, what crossover?. I can't get any audible sense of one being there, again thanks to the superb time alignment of the tweeter and woofer and some clever realtime adaptive slope technology. In fact the upper midrange around the crossover point and above is probably the most distortion free part of the A21-M's frequency response.
Another thing thats very impressive is the amp design. Mounted on suspended pins (apparently to reduce microphonics), the Class-G amps in these offer Class-AB quality of sound, but with Class-D efficiency. It's quite extraordinary, you can crank them up super loud for some time, put your hand on the metal backplate and its barely luke warm. Very VERY efficient amps.
If I had to be picky and think of things that could be improved, I'd say that perhaps the 3rd harmonic distortion on frequencies between 900-1.7K could be a tad lower (not that they're unusually high by any means). Also the general background hiss from the tweeters is audible @1m listening distance in a treated room. If you like your monitors dead silent at close range then this might possibly bother you, but I personally sit @1m distance away and its acceptable for me.
For its price point though its hard to find equivalent rivals that sound as good, especially for their relatively compact size in terms of depth. These clearly highlight the strong colourations and veil over details of lesser monitors, whilst snapping at the heals of the likes of ATC and Barefoot.
In short, fantastic precision sounding monitors, brutally honest in many respects. Well worth the money and highly recommended.