Pros: Supremely comfortable, light weight, natural laid back sound, wide soundstage
Cons: Lacks a little sparkle, bass slam could be tighter, flimsy feeling build
Along with the summary below, I have posted a comparison review of the MA900, Audio Technica AD900X and AD1000X here:
I've also got a youtube review of the MA900. If you like the video check out my channel for more reviews :)
The build of the MA900 is interesting. The headphone feels very light weight and almost flimsy in the hand. This isn't because it is badly built - on the contrary build quality is quite decent. It is the proportion of the parts, the super light weight and the way the frame is so flexible which makes it feel flimsy. As soon as you put them on your head you realise how much effort has been put towards minimising the MA900's weight though, which is almost enough to forgive them a little. That said if the MA900 was at least made out of metals it would have inspired more confidence, even if it were a little heavier.
The MA900 has a neutral sound, slightly on the warmer side but overall very balanced and generally inoffensive. The bass has good definition but doesn't dig terribly deep (as per most open headphones) and the mids have a somewhat dry tone, whilst lacking a little extension at the top. They sound great with female vocals. The MA900 actually sounds like a Sennheiser HD650 with less lower bass and more forward upper mids. Because of the steeply angled driver the MA900 has a open and relaxed soundstage, with good definition and instrument placement. However with the relaxed treble it does sound a tad more intimate than say, the AD900X or AD1000X. Overall they are very agreeable and the main negative that can be said about the sound is that it might be too conservative. It's perfect for hours and hours of listening with different genres, and the comfort helps a lot in that regard.
I love the MA900 as a workhorse headphone and it's what I wear most of the time at home on account of its comfort. The build quality is okay but won't inspire any collectors of Sony gear. I really think the MA900 has been overlooked on Head-Fi on account of initial bad reports about the build, and though it's not the most exciting of cans it certainly is a fantastic all rounder. At the current Amazon Japan pricing it's a steal.