I just got my Betas last week - and wanted to do a review after 50 hours of burnin. Perhaps they'll continue to improve with more playing time, but I expect that improvement to be marginal. Bear with me as this will be my first full review on head-fi.
Build Quality - I'm really impressed with these. I have $60 plus earphones that I wish would borrow some of the build quality features these have. Most importantly the metal sound channel that holds the tips - with certain tight fits on other earphones, I've been concerned about breaking that nozzle - but not on the Betas. One thing that no one's commented about (that I've noticed) is the fact that even if you don't use the metal filter at the end - there's a second filter lower on the stem that protects the drivers. Too many earphones don't even have one metal filter - some leave the driver altogether exposed (meelectronics ai-m9) or filtered with paper (head direct RE0). Granted, this would only be an issue with excessive use and earwax problems - but still, it makes me more comfortable to have a metal screen regardless. The one knock I have is the somewhat cheap cable - instead of the common one piece "round cable" with a piece of plastic or metal to hold the V - these use the two strand flat cable that you have to split to reach each ear. That said - worn over the ear - I sensed no microphonics.
Sound Signature - It's definitely dominant in the "highs" - they were even a little shrill, so I recommend using the optional filter and/or some foam in the stem. I actually prefers mids and highs to bass - but I found the highs so shrill as to be fatiguing without the filter. I found the mids a little recessed to be honest. Voices didn't come through well and got a little lost in the instruments I'm afraid. Bass was actually pretty decent - there's a good amount of it, though it's not as tight/accurate as some other phones. Bassheads might not be happy with the Betas out of the box - but I think everyone else might be.
Sound Stage - I found the sound stage to be average - which was nice, because I thought the deep sound tube might be inserted too deep to provide an adequate spacing. No complaints.
Detail & Instrument Separation - These are not the most detailed IEM's I've heard, but they're solid for the price range. That said, I found that in certain fast tracks, rock and metal, the background music could devolve into noise as the driver couldn't resolve all the separate instruments. You really have to be focusing on it, however.
Burnin - These are the 2nd iem's that I saw huge improvement with after burnin, the others being the value priced Lenntek Sonix. I hated the sound out of the box - they sounded veiled to me. After 50 hours, the veil tore, the highs had tamed down, and the bass started coming out.
Hiss - I've made a pest of myself over the Soundmagic PL30's (which I didn't like) so some might be happy to know that the Betas don't hiss anywhere near as much. With my more expensive amp - I picked up a slight hiss at high volumes (without a source) but it was barely detectable when looked for. I don't think anyone should have an issue with these. They have a high sensitivity, but the standard impedance (16 ohm).
Overall Value - I think these are solid for the price range. They may not be my favorite sub $30 phone for sound quality (meelectronics ai-m9, m6) but these seem to trump those for build quality, accessories and packaging. I'd be more comfortable giving these away than the other options. I think these make a great gift. I'll be happily giving these to my sister for Christmas.
One more note - in the first minute after burnin, these sounded so good to me that I was wondering if I wasted my money on $80 Re0's. But within a few minutes I was picking up the differences and shortfalls. So someone wearing basic iphone buds and no experience with better earphones, should be very happy with these.
