I only just recently listened to these, and boy was I impressed. I had the UM3x, W3, SE535, SE425 on hand for comparisons, and the MMDs more than stood up to the competition. They're the most expensive out of the five but dang, I was ready to hand over cash only to be told that I had to wait for stock to come in. Let me explain.
The bass is sublimely powerful, deep, and very well controlled. More importantly, it does not bleed into the midrange which means your vocal/instrumental texture and timbre are largely preserved. The midrange in general sounds mellow, detailed and clear, yet not overly warm. It will readily reproduce the rasp, husky voices of our favourite vocalists. The high frequencies retain a particular sparkle which in turn is not overly sibilant. Overall, these really impressed me. Their powerful sound makes for a very entertaining listen, and the clarity was something I had previously not encountered in a dynamic driver IEM (including the IE8, high end Sony, etc). I also enjoyed how alive recordings sounded, and the speaker-like presentation.
The W3 and SE425 sound pretty congested in comparison, and lacked in refinement. The SE425 in particular was too bright. The upper midrange stood out like a sore thumb. Neither gave the impression that I was listening to a high-end earphone. To be honest, I was very surprised given the glowing reviews that they received, and also the common assumption that balanced armature drivers tend to be more capable of reproducing detail. I guess I was wrong. As for the UM3x, these I thought were much more "neutral", but still lacked in overall refinement. Sure, they were more detailed and more true-to-recording than the latter two, but I expected a lot more from them and was both surprised and underwhelmed given their lofty placement in Westone's UM lineup. Lastly, the SE535 was the only earphone that really stood a chance against the MMD in terms of enjoyment and refinement. The SE535 has a much more balanced sound signature and will suit a wider range of genres. The bass, like the MMD's does not smear the midrange detail but isn't as powerful. Boy Shure they improved the SE535 both physically (the cable!!) and sonically since the the questionable E500 PTH (which I have owned twice and subsequently sold, twice...).
Sadly, the MMD is not perfect. Yes. It is a very addictive, powerful sound. Yes, instruments come alive. And yes, the clarity and overall realism of the sound far exceeds even some of its more renowned rivals. But the bass is too much for some genres, namely classical music. Anything that involves a cello or lower pitched instrument simply sounds silly. The emphasis put on the lower midrange/bass is inappropriate and renders the MMD pretty much unlistenable. I'm a classically trained musician myself (amateur/serious "hobby" violinist) and whilst the MMD is great for solo violin - maybe still a tad too warm? - but I wouldn't be reaching for these for anything symphonic. Having said that, Norah Jones, Michael Buble, general rock/pop/dance simply sound sublime.
Physically, the whole IEM looks pretty sweet, though the cable does look like it could be made a little sturdier. I also like the presentation box and every extra "freebie" thrown into the package. Lifetime warranty? Tick.
For everyone who loves jazz, rock, Jap/Chinese pop and RnB, I urge you to go try the MMD. Listen for yourself. Even to those who come from a background of high-end audio and custom IEMs, these might be worth checking out. For purveyors of the perfect, true-to-recording sound, these may not appeal as much. However at this price range, true high-end refinement is really difficult to find and if you can accept the amplified bass, these will still wow you with their open, speaker-like, powerful presentation. I will go as far in saying that to my ears, these are certainly more refined than the W3 and SE425. The UM3x's more neutral presentation may be more appealing to some (does more things to an acceptable standard, but nothing really well) and the same goes for the SE535, though, the latter does come close in clarity and enjoyment. I think what will put people of the MMD is its price and sound signature, especially fans of classical music. It seems awfully expensive to buy this just for particular genre(s) of music, but heck, who cares if even 5 minutes of Louis Armstrong will make your spine tingle and your heart beat faster?! :D
Monster, you have outdone yourself. I, like many others, have spurned Monster in the past. Looking back at the early threads re: release of the Monster line of IEMs, I see many Head-Fiers bad-mouthing their products even before listening themselves. Some even went as far as calling these pieces of ssss. It's like what happens whenever Bose, B&O are mentioned. Having finally auditioned these, I feel I have really learned a lesson in humility. I didn't expect this level of quality from what I've always considered a pretty "consumer grade" company. If these were cheaper, it should have the Westone management trembling in their beds at night. Shure don't have as much to worry about as the SE535 is pretty solid and can be found at very reasonable prices.
Got to go. Hope I didn't go on for too long.
Edited by milkpowder - 4/16/11 at 5:44am