[UPDATE 11/29] Well, after listening to the CX250 for the past several days, I've come to a slightly different conclusion than I did during my initial impressions. I'm not sure if it's burn-in or further acclimation to the sound, or perhaps more likely, better fit with the included silicon tips. Needless to say, I find the CX250 very interesting indeed. I'll add my latest evaluation after the first impression comments below.
[UPDATE 12/27] Here's kurtzi's impressions on the CX150, which appears to be a volume control-less version of the CX250. Also, for those interested, here are the links to Sennheiser's descriptions of the CX150 and CX250.
I am not exactly sure what compelled me to purchase these little-known budget Sennheisers, but now that I've had a listen I thought I'd briefly share some first impressions.
After wrestling with the earphones out of the oddly packaged box, I was surprised at just how tiny these canalphones are. Indeed they appear to be smaller than even the CX300. The volume attenuator however is quite large. (Anyone who has had experience with any of Sennheiser's volume control-equipped Street series earbuds knows what I'm talking about.) The cables used on the CX250 much more robust than the CX300 but unfortunately just as microphonic. The package also includes a nice durable cloth pouch for storage.
Honestly, when I first put these canalphones in my ear, I was expecting nothing but big bass bloat with no mids or highs. That's not to say that the CX250 isn't bassy, because they certainly are. What I didn't expect was a decent midrange that seems to be more transparent and more detailed than the CX300's, perhaps because of the CX250's comparatively lessened midbass quantity. The mids do tend to be slightly grainy and can still be a tad distant at times, but it's acceptable. The upper mids however can be sibilant and downright shrill at times, though I'm hoping that some burn-in will lessen the pain a little. The treble seems to be more articulate than the CX300 as well. Soundstage is smallish (mostly vertical) and lacks depth but is tolerable. Overall, I actually prefer the CX250 to the CX300 as the former sounds far clearer though it can also be more fatiguing.
After about 20 hours of use, I'm still unsure of whether I like them or not. Really, at about $22 shipped, it's hard for me to complain, though it's also hard to recommend without reservation. But what struck me as significant are the differences in presentation between the CX250 and CX300. A refinement of the sound signature of the CX250 -- removing some of the spikes in the frequency range, smoothing out the midrange, lessening the sibilance, and widening the soundstage -- could result in some interesting products down the line.
FINAL THOUGHTS 11/29
As I wrote earlier, it seems that the CX250s are finally putting out a more likable sound. Firstly, I have become quite impressed with the amount of detail these put out, particularly in the midrange and treble. There seems to be quite a bit of speed and an overall lack of decay compared to the typical Sennheiser canalphone, which quite honestly continues to confuse me. This makes the CX250 seem far more articulate than even my beloved CX550. Of course, this general lack of decay (and lack of midbass warmth) also amounts to a leaner sound than most CX-series earphones. This, combined with fit issues, probably accounted for the thinness that I was experiencing earlier. I should also note that there is a bit of an upper mid spike, which creates a bit of brightness and also a slight amount of sibilance and harshness.
The bass is very interesting in nature since, as discussed in the first impressions, it seems to stay out of the way for the most part. It is not bloated in the sense that it bleeds into the mids, and about 85% of the time it isn't too excessive. However, if a track calls for any amount of bass at around, say 30Hz, suddenly a large invisible subwoofer that wasn't in the room prior starts spitting out a ridiculous amount of low frequency impact that usually results in headache and fatigue. It's really odd but also strangely amusing.
I have written before that the soundstage of the CX250 is rather smallish with and mostly vertical in nature, but I've since figured out that it was mainly due to an improper fit. Now that I have the fit straightened out, I have to say that while the stage is still a bit small, the imaging is actually quite impressive for such an inexpensive phone. Within the small confined space, instruments seem to line up rather accurately from left to right, and any individual part can be followed with relative ease.
The CX250 is just a strange canalphone. According to Sennheiser nomenclature it should be inferior to the CX300 yet it offers a sound that is cleaner and more detailed than the "greater" CX model. To my ears, if it wasn't for the sometimes excessive bass, I believe that it may come close to the CX550, the successor to the German company's former in-ear flagship. The fact that it sounds nothing like a Sennheiser CX and that it somehow emits a sound that is both analytical and bassy equates to a product that seems slightly misguided. But that's probably why I like it.
If you don't mind trying something a little different and enjoy detail, speed, and bass, the $22 CX250 may be worth a try.