I had long been planning to repair my set of HP-1s that had a broken driver. Couple of days ago now I finally got hold of a pair of HP-1s (thanks Tasoeur and welcome, by the way!) and since I now have a measurement rig available I thought I could very well publish measurements of the stock phones as well as the modded pair.

Pic1: B/W Ebony HP1s (open back, with HM5 velour pads)
Pic 2: Stock HP-1 - Left
Pic 3: Stock - CSD
Pic 4: Modded - Left
Pic 5: Modded - CSD

Having heard 2 aniso and 1 normal HP1 (all modded to their potential.....by Gurubhai), i have lost interest in commercial headphones. LCD2 and HE400 are the only expensive headphones i have experience with and the HP1 kills them both with ease. HE400 feels like a joke in comparison while LCD2 though good is too shelved.

Great looking headphone, stratos. I have always wondered about an open back Yammie myself.So, what do they sound like?

Having heard 2 aniso and 1 normal HP1 (all modded to their potential.....by Gurubhai), i have lost interest in commercial headphones. LCD2 and HE400 are the only expensive headphones i have experience with and the HP1 kills them both with ease. HE400 feels like a joke in comparison while LCD2 though good is too shelved.

LOL, didn't mean to turn you or anyone away from commercial headphones. Like I said during the meet, I am planning to purchase a HD800 myself. I am really curious how the new OTL performs with a more optimal load since it has easily bested all my previous amps even with the orthos.

So, what do they sound like?

Even if it sounds like hyperbole, the sound that these produce is deeply satisfying to my ears. There is nothing that immediately strikes me as bothersome or wrong.  When I listen to them, and I have done so for quite some time since I finished them, I become immersed in the music. They sound extremely natural, with good timbre and the drivers provide nice resolution and instrument separation. Using the thicker and wider HM5 velour pads the soundstage, which is no wonder,  is greatly improved over stock. Bass is deep and extended, does not overblow, male and female vocals are rendered marvellously, the signature being a little laid-back yet not warm, there is no sibilance or false detail, and surprisingly, nothing I would have expected beforehand,  there is a lot of air.
 I guess, I have found a new favourite.

The highs can be tuned quite a bit by using a kind of felt fazor inside the cups. I will include twoquick and dirty measurements to show this. My ears, though, tell me, there is nothing wrong with the highs without any fazor. The peak around 7kHz is broad enough, there is no ringing, the CSD graph shows quite some speed, resulting in a very clean treble.