The HD448 is of similar airiness to the HD238 with the foam removal mod, with less voluminous bass. The bass is still present, just leaner. I can't hear any sibilance whatsoever with the HD448. Sennheiser did a fantastic job in the sound signature of the HD448's. The highs are bright without being sibilant or harsh. Also on another note, I am somewhat convinced now that my HD238's have some distortion problem with the bass notes, so I will eventually have to get the 238's checked out by Sennheiser. But the HD448 has no problem whatsoever with producing clean bass. However, one may find the bass somewhat lacking in volume, especially if they are used to headphones like the HD650. However, the high level of clarity in the mids and highs make up for this IMHO, and they surpass the HD595's by a long shot in the mids and highs and are of similar quality in the bass, maybe perhaps cleaner, but a bit leaner than the HD595. Also, one additional note is that the driver is very similar in size and design to the driver in the HD238, perhaps only different in tuning. Judging by the frequency response curves of the HD448, it seems as though Sennheiser created a very nice sounding blend of a tweaked curve of a lower-end Ultrasone from the highs down to 200 Hz or so, then the Shure SRH440 from 200Hz to the lowest bass. Despite the appearance of a considerable bass roll-off in practice the HD448 is actually very balanced, with ample bass, just a bit attenuated comparatively to the HD595. They don't have the imaging depth of the HD595, though the imaging is actually similar if a hair larger than the HD238, and a touch more "open" sounding. However, the highs and midrange of outside sounds are attenuated pretty effectively. The bass of outside sounds are less attenuated than the highs and mids, and can leak into the listener's perception if loud enough. I would say though that the isolation is a bit better than the Denon AH-D1001, but if you are playing music very loud the HD448 will leak some sound out, but not nearly as much as an HD238 at the same volume level. Comfort is good, but not as good as the HD238, specifically the pleather on the HD448 feels much cheaper than the HD238, and downright cheap compared to a Denon, but is still soft to the touch. If you recall headphones like the HD201 or HD205, the pleather is almost the same as those. It isn't as comfortable as the HD595, due to the pleather, but is still pretty comfortable, with ample room between my ears and the driver, though people with huge ears might feel that the earcups are a bit small (though they are larger than the Denon AH-D1001) and may experience a less comfortable fit than I did. I hope this, my 500th post in my 8 years since joining this forum (yay), has helped.
--Eric
