The Sennheiser HD25-1 is quite the opposite of the ESW-9. If the ESW-9 is laid back, the HD25-1 is in your face. People have called it as the “Grado” Sennheiser due to its presentation. The HD25-1 can be considered neutral, when compared to the highly colored ESW-9. The HD25-1 delivers a lot of impact in the bass, and it still remains, even among full size cans, to have one of the strongest and most focused bass punch. Keep in mind that the HD25-1 is not a bassy headphone, it just happens to have a great bass punch. Its frequency response is slightly prominent in the upper midrange and lower treble frequencies, though the treble “attack” is not as strong as what you’d get from Grados.
The HD25-1 may have the smallest soundstage compared to the ESW-9 and the SRH-840, but it has the best instrument separation out of the three. And compared to the other two, the Sennheiser HD25-1 may look like the underdog, but in reality it has the biggest potential. Having removable connectors like the other Sennheiser HD series makes cable upgrades easy to perform on the HD25-1. We used the HD25-1 for the Sennheiser Cable Shootout, because it is more revealing to cable upgrades than the HD650 is. Moreover, while I’ve never heard a balanced SRH-840 or balanced ESW-9, the HD25-1 in balanced configuration is pretty awesome. Finally, the HD25-1 has a certain energy that makes it simply unbeatable for Rock and Rap music. It still plays other genres well, but it especially shines for music with fast paced music that prefers an in-your-face presentation.
The Shure SRH-840 can be seen roughly as a middle ground between the smooth tubey ESW-9 and the in-your-face and impactful HD25-1. The sound is mostly neutral. It doesn’t add a lot of coloration like the ESW-9, and like the HD25-1, it is quite honest and will show a sibilant recording to be sibilant. The SRH-840 doesn’t put an emphasis on any frequency range, but it seems to have enough of everything: good midbass punch, good mids, good sparkle on the treble, and overall it is a great all-rounder headphone.