Pros: Detailed sound. Lovely mids. Wide assortment of tip that isolate well.
Cons: Until modified, sounds tinny. Perception of bass is lacking.
At first I was disappointed. I'm not a bass head, so I was looking for an IEM that would accurately present the sound coming from my Astell&Kern AK100. The se425 presented a very clear, middle focused sound with excellent instrument separation, but although bass was present, it was not enjoyable or punchy. I could help things a bit by doing a V-shaped EQ, but then I felt I was missing out on the nice, detailed mids the se425 is good at. To make matters worse, although the set comes with a pletlhora of tips, none ever seemed to ever be very comfortable. I came very close to buying an se525 instead, as it supposedly has a better bass and treble extension, but before then I luckily did two mods that totally saved these from the resale heap. I replaced the stock cable with a 6N ofhc cable I purchased off ebay. It worked in that it extended the bass somewhat, and the soundstage also became a little wider. Actually, the purchased cable also made the psoitioning of the earbud different (vertical to the ear canal rather than horizontal) and that made it more comfortable for me. Still needed some EQ, but the sound had improved somewhat. The second mod was trickier, but I'm so glad it worked. For it, I used the rubber tips from my JVC HP-FX500, which I found to be very comfortable and soft, but rather boomy on the FX500. As the JVC tip is made for a thicker nozzle, I took one of the medium sized olives that came with the se425 (it came with two pairs of these anyway), stripped the foam, and used the inside plastic tube to bridge the gap between the se425 nozzle and the JVC tip. Voila. Healthy bass without EQ. By this I mean I'm getting appropriate focus across the range, from bass to treble. Electronic music, rock, etc, now sound warmer, more full bodied, with a good soundstage and the same amount of detail. Isolation is still good. I compared this Frankenstein monster to se525 at the store that have had plenty of burn in, and I just knew these mods had made the se425 simply better. Also compared to JVC FX-700 and Audio Technica ATH-CKS1000. it beat both although the CKS1000 (also well burned in because the store continually pumps techno through it) put up some stiff competition, and that is actually a single driver IEM! That said the FX-700 was also a very nice sounding IEM. The se425 has performed well with most genres: I listen to orchestral soundtracks, latin music and rock, some electronica, classical, and jazz. HD tracks, Flac and mp3@320 need only apply. itunes' m4a is okay, but tends to sound a bit harsh, I think. Other than that, It does not seem to forgive low quality recordings. So it took some tinkering, but now The se425 is here to stay.