Pros: New modular cable design feels very solid and well executed, relatively flat sound signature, Bass is present but not obtrusive.
Cons: Getting a proper fit is difficult at first.
These are my second pair of Shure IEMs. I had enjoyed the SE210s for a long time before taking the plunge on these. Since these are meant to be worn up only and the cable rotates freely where it attaches to the monitor, it took some getting used to the new cable design. Sound quality is definitely leaps and bounds above the SE210s. The bass is IMO much more substantial on the 425s but very fitting to the music I listen to (all shades of rock). I tried sampling some electronic music with these IEMs and was quite impressed but I will warn that these IEMs do not produce "Pounding" bass.
Design and Fit
The new modular cable design seems almost perfectly executed - The cables break free from the monitors easily but will never remove themselves. The added memory wire adds some comfort and assistance when putting them on and helps them stay in place. The cable has a bit more weight than that on the SE210 but it is more flexible and microphonics are almost nonexistent.
As expected from Shure IEMs supplied are a pair of triple flanges, three pairs of silicone tips sized S M L and four pairs of Shure's signature foam "olives" again in size S, M, and L but with an extra medium set preinstalled on the earphones. I prefer the large Olives on this set while the medium Olives provided me with the best fit on the 210s. With some trimming I'm sure I could get some more enjoyment out of the triple flange set, but the large olives have a slightly more warm sound quality to my ears and are more comfortable for extended listening.
My biggest worry when buying the 425s without hearing them before hand was that the bass was going to be under emphasized but that is surely not the case. I was pleasantly surprised that the bass response was everything I could have wanted out of a pair of IEMs; Present, detailed, but not all-consuming.
Like everyone says, the mid range is clearly the most emphasized. Very smooth midtones that lend to amazing vocal clarity. There is roll off on the high frequency but its not distracting, nor do I feel like it takes much from the listening experience. I personally like a little added brightness to most headphones so with a touch of the EQ these IEMs are very moldable to my tastes.
The SE425s quickly made themselves my new favorite pair of earphones. The sound quality fits my musical preferences very well and with a little acclimation they are quite comfortable for extended listening. I managed to pick up a set for $230 before tax which in my opinion is a steal. I was however more than prepared to pay $300 for and at that price I still feel like these are money well spent.