These are a very good dynamic IEM, and when I say dynamic, I'm not just referring to the type of driver. The sound is very forward, very exciting at first, and I was immediately struck with the immense sound-stage. The drivers are very responsive and demonstrate better speed than I expected. If you love any form of electronica, buy them. I was hard pressed to find fault with any specific aspect of the sound while I was listening and the bass is incredible. However, I was quickly fatigued by listening to them and afterwards my head felt full of grit. I gave them about 50hrs of burn-in and used no EQ while listening.
 
Because of the light weight, I had no problems getting a comfortable fit with the included eartips. The included case is heavy and possibly worthless if you go with a Comply eartip.
 
I really wanted to love them considering the bargain price (refurb), but in the end I sold them.

[size=10pt]These were just the second set of IEMs I bought, the first being Etymotic's 4S about 10 years ago. This was my first purchase intended for portable use (with a Clip +). At first, I was blown away by the low end, not in comparison to a real headphone set up, but to my 4S plugged into a laptop watching Netflix. Hey, I'm just being real. My Etys were, at first, a curiosity, nice for the occasional foray into 80s new wave, then essential to avoid pissing off the wife while I watched deeply disturbing Korean films. So I'm not use to hearing bass and was blown away with the impact of the RP-HJE900. I've since pulled back my enthusiasm. I can, however, unequivocally say these do not suck b*lls. And depending on your musical tastes, source recording quality, and personal proclivities, you may find these one of the all-time great steals. These phones are frequently accused of being sibilant. Depending on the listener and source, they can be. People have different ideas of what sibilance is. I did find the highs harsh on certain recordings but constrained with EQ and a little foam,  and more importantly, proper fit. These earphones will always have a place in my collection, if nothing else because they make for the perfect backup. They do a lot right and little irreparable wrong. [size=10pt]I think a lot of us owe dfkt a six pack for bringing these to our attention. Thanks for being reddish and not always grumpy.[/size][size=10pt] [/size][/size]
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[size=10pt][size=10pt]        dfkt [/size][/size]
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I love these for watching movies at odd hours or on the laptop away from home. They're so comfortable that I can wear them for 6-8 hours straight. Unfortunately, I find them totally unacceptable for music, though they're a better fit for portable use or the computer because of EQ. Several posts compared the sound quality to etymotic's 4 IEM, uh, no way in hell. Proper fit is crucial to both comfort and sound quality -- read the included instructions. Additionally, make sure you dig in the case pouch pockets for the foam socks - without them the bass tubes feel very cold and uncomfortable when placed against your ear canal opening.
 
A month after getting them the right channel went completely dead. I'm an old f*rt, so I know how to take care of my equipment. Very disappointing.
 
I called Sony Support and after much wasted time was finally requested to send them back to a Sony Repair Center in Laredo, TX. Two weeks later Sony told me they would not repair the headphones and were out of stock, therefore, they would generously refund my $150. Great. What about the $17 bucks I spent to send the damn things, not to mention the $15 for the original shipment? I never had a good impression of Sony and this just ices it. Decided to take the things back and try to fix them myself.
 
Opened the housing, pulled the tape from the wires attaching them to the back of the driver. The wires looked in good shape, and the solder points were still intact. Since everything looked OK I decided to test them again. They were now working -- or more accurately, stopped grounding. Heat shrinked  the wires put the housing back together and I was in business again. Rating has been re-adjusted.
 
 

 Purchased as a demo. I find this amp to be an excellent mate for Denon D7000.