When I discovered how great the HD25-1 was when driven balanced, I quickly realized that even though the improvements were great, still it was not really practical to have a balanced HD25-1 set up. (At that time I was driving the HD25-1 through the balanced Beta22 with a stock HD650 cable reterminated to XLRs) The HD25-1 was a portable headphone, and back then we didn’t really have any way to have balanced drive on the move. While at home, and with big balanced desktop amps, people would rather listen to their balanced full size cans, and so the whole thing didn’t really take off.
The HD25-1 is probably one of the best portable headphone, even today. It’s a very successful design by Sennheiser, and it has a huge following. It’s quite a departure from the usual Sennheiser laid back and darkish sound. But the biggest weakness of the HD25-1 is the size of its soundstage. The driver is placed very close to your ear, and often you get a feeling of too closed in. Even though good aftermarket cables can help to give a more open sound, it’s effect is quite marginal.
When Ray announced his RSA Protector, one of the thing that came up to my mind is that the HD25-1 now can be driven balanced while on the move, and that would really make one of the most kickass portable headphone system. It has a good rugged body, one of the best sound isolation for a portable, a superb sound quality with one of the cleanest and punchiest bass, and now the soundstage size would be improved, as my experience has been with the balanced Beta22. Of course I didn’t expect the tiny Protector to match the Beta22’s performance, but I was hoping to hear similar effects.
Finallly I was able to try out a HD25-1 driven in balanced from the Protector. I still hasn’t made an appropriate cable for it, and so the connections was made using a stock HD650 cable reterminated to XLRs, then an XLR adaptor to the Protector connector. Far from the ideal cable set up, but it gets the job done, as I really wanted to hear how the HD25-1 sounds, balanced, from the Protector. Okay, it wasn’t really a mind blowing change as I have expected (The Beta22 has this ability to make any headphone awesome sounding), but the change is there. Soundstage was wider, even compared to the single ended Cardas cable, although the depth doesn’t change much. There was also a slight increase in bass presence and punch. Overall, was it as mind-blowing as I had expected it to be? Frankly, it’s not big enough to warrant getting a Protector just exclusively for your HD25-1. But if you happen to have the amp and the headphone laying around, do give it a try.
System for auditioning:
Headphones: Sennheiser HD25-1, HD650 cable reterminated to XLR, DIY XLR to Protector 4-pin connector, DIY Cardas blue cable reterminated to 1/8″ Switchcraft.
Source: Ipod Classic, Hifiman HM-801, Teclast T-51
Amplifier: RSA Protector