RSA Protector and Sennheiser HD25-1

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

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9 Comments

  • Reply January 3, 2012

    Noppon

    Hi, I am newbie here. Just get some questions about balanced HD25-1. I have an iPod classic 5G, PB1 amplifier and HD25-1 ii. How much the sound will be improved if I use an HD650 cable terminated to hirose (from iBasso) and drive the HD25-1 from PB1 in balanced mode?

    iPod classic –> PB1 –> HD650 cable terminated to Hirose –> HD25-1 ii

    also

    Macbook pro –> DB1 –> PB1 –> HD650 cable terminated to Hirose –> HD25-1 ii

    Is it worth to buy the HD650 balanced cable? Thanks in advance.

    • Reply January 3, 2012

      Mike

      Personally I wouldn’t worry about it. It’s too much of a hassle to have in a portable set up and the improvements are not that spectacular. Furthermore I think the PB1 and the HD25-1 doesn’t make such a good pairing. 

      • Reply January 4, 2012

        Noppon

        Thanks Mike for your rapid response. Actually, this is my second post on Headphonia, but I did read many of your reviews here. If my memory well serves, you mentioned before in another post that the PB1 is too bright for HD25-1. So do you think the HD598 will match and get the benefit from PB1? I usually listen to Pop, Acoustic and Vocal musics.

        In addition, I am also planing to purchase either cMoyBB or O2 to use with HD25-1 as well. What do you think?

        In conclusion,

        For potable usage: iPod classic –> cMoyBB or O2 –> HD25-1 ii

        For home usage: Macbook pro –> DB1 –> PB1 –> New headphone (what do you recommend between ¥15,000 – 25,000 ?

        Thanks again for your suggestion.

        • Reply January 5, 2012

          Mike

          Hi Noppon,
          I would choose a warmer amp for the HD598 like the O2 or the cMoyBB. The O2 should be a much better amp than the Cmoy but its dimension is not very portable. On the other hand, I think the upcoming JDSLabs C421 is going to be perfect. Great sound quality with a slim case. I have one C421 with the OPA2227 opamp, and I think it’s much better than the Cmoy, while just a little below the O2. The selling price should be around $180.
          Here is a link for the preorder:
          http://blog.jdslabs.com/?p=179

          • Reply January 5, 2012

            Noppon

            Thanks again Mike for your kind suggestion and quick reply!

            Should I get an AD8620 opamp version based on their statement?

            “Two options are available for the primary stage opamp: AD8620 or AD8066.

            Our #1 choice for c421 is the AD8620, which gives smooth, refined output and excellent imaging. A/B tests deemed the AD8620 more favorable than the OPA2227 and AD8397! 

            The AD8066 is slightly less transparent, with similar highs but greater emphasis on bass. AD8066 is better suited to driving especially high impedance headphones (300+ ohms).”

            • Reply January 5, 2012

              Mike

              I don’t know why John said that, but I have two C421s here and I clearly feel that the OPA2227 is much better. Thing is I don’t remember which opamp the other C421 has (gotta look it up).

      • Reply January 4, 2012

        Noppon

        Never mind for my questions because I just dig in your previous post about the pairing between HD598 + PB1 and also cMoyBB + HD25-1. How about O2? Will it be more matching to the HD25-1? In addition, I’d like to hear your comment on the comparison among cMoyBB, O2 and ZO2. Which one is the good pairing to HD25-1 or HD598. Thanks.

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