We listened to the SR225i headphones over an Onkyo TX-SR805 receiver, a Schiit Audio Asgard headphone amplifier ($249), and an iPod. The Onkyo sounded more laid back and mellow compared with the Schiit Audio amp, so yes, the SR225i's sound quality changes, depending on what it's plugged into. That said, we'd consistently characterize the SR225i's sound as clear, dynamically alive, and very open. Or, put another way, it doesn't sound like all of the sound is stuck inside your head.
Morphine's "The Night" CD immediately told us a lot about what the SR225i was doing right. Dana Colley's baritone sax sounded deep and fully present, as if there was nothing between the sax and our ears. It was easy to follow Mark Sandman's gracefully sliding basslines, and Billy Conway's jazzy drumming had a lively attack. Treble detail is exceptional, so you hear the cymbals' every shimmer and sparkle. The SR225i's treble is more detailed than average, and some listeners may find it too bright.
The SR225i brought out the best in well-recorded rock music, but a heavily compressed and harsh recording, like the new Arcade Fire CD, "The Suburbs," wasn't particularly enjoyable. The recording's flaws were hard to ignore over the SR225i, but the flaws were much less of a problem with the Ultrasone HFI-680 full-size headphones. That headphone's softer treble response and bassier bottom-end took the edge off the sound of "The Suburbs" CD. The HFI-680 was far from perfect; it's a closed-back design, so it had a more "canned," closed-in sound than the SR225i headphones. Even so, the HFI-680's easy-going nature made harsh recordings more listenable than they were on the SR225i.
On good-sounding recordings we definitely preferred listening to the SR225i. Puente Celeste's "Nama" CD is a stellar audiophile recording, so the voices, clarinet, accordion, acoustic guitars, bass, and percussion on this world music CD had an almost 3D presence and solidity with the SR225i. Switching over to the HFI-680, the recording's soundstage was squashed flat and the treble wasn't as clear. We had been listening over the Onkyo receiver, but from this point forward we used the Schiit Asgard headphone amplifier, which improved the sound of the Grado and Ultrasones. We still preferred the Grado on better-sounding recordings, and the HFI-680 on compressed rock music.
For the SR225i's home theater trials we watched the "Mad Men Season 3" Blu-ray disc and quickly forgot we were listening to headphones. The office scenes in the show's Madison Avenue agency were filled with the sounds of clicking typewriters, ringing telephones, and hushed voices that seemed to come from outside the SR225i headphones.
It may be a full-size headphone, but it sounded wonderful hooked up to an iPod. The design is unusually efficient, so it can play pretty loud, even when driven by an iPod's puny headphone amplifier. True, the headphone's size may be enough to put off some from using it on the go--and the fact that you need an adapter to connect to the iPod is a big turn-off--but when the SR225i's big sound and vivid clarity are available for portable use, it may be hard to resist.
The SR225i brings with it a notable list of caveats, at least for listening on the road: the dearth of a 3.5mm plug, an open-backed design that lets in external sound, and a somewhat unforgiving disposition to compressed music. On the other hand, it also exhibits top-notch sound quality, and we really like the idea of paying for quality electronics that are built right here in our back yard. We think the Grado SR225i is a great set of headphones, and we enthusiastically recommend it--but it's certainly not for everyone.