First off, thanks to hembergler for generously mailing me free 6-micron mylar, spritzer for his expert advice, and Joerg Baar for being a living, breathing repair manual. They helped make refurbishing these headphones possible.
The Micro Seiki MX-1 is composed of the MS-2 headphones and MP-1 amplifier, supposedly produced by Stax in exchange for Seiki's UA-7 and UA-9 tonearms. For a general overview, visit this link: http://www.thevintageknob.org/THEVAULT2/MS2MP1/MS2MP1.html
Originally, the diaphragms were made of polyurethane, which had long disintegrated before they arrived at my workbench. My refurbishment job consisted of disassembly, removing old polyurethane particles from the chambers and stators, recreating the diaphragm with mylar, coating the diaphragm, and reassembly.
Disassembly was simple. The earpads unlock with a slight turn, and the rest is intuitive. The hardest part was stretching, mounting, cutting, and coating the mylar. My final iteration used 1.4-micron mylar from turnertoys.com, available in a 12.5" x 10' sheet for $11.50. As a coating, I used 80 mL water + 20 mL PVA glue + 5 drops of carbon pigmented ink, a formula roughly based off the one popularized by this DIYaudio thread: http://www.diyaudio.com/forums/headphones/132573-has-anybody-made-els-headphone.html Since the mylar tears easily, even when cut with the sharpest of "I can push-cut paper" blades, I used a red-hot needle to shave off excess mylar after mounting the film.
APPEARANCES, BUILD, COMFORT: picture borrowed from TAC
These are sharp looking headphones, both sturdy and lightweight. Padding is minimal, but the headband swivels open to distribute weight. The earpads are soft vinyl, and provide a seal without clamping. I used the Chesky Ultimate Demonstration Disc, ran through a modest NAD integrated amp out to the MS-2 / MP-1.
I'm no expert, and I'm speaking from limited headphone experience. I'll do my best to compare them to both what I've heard from other headphones as well as what I've heard as a percussionist in concert bands.
My reference headphone for frequency response is the Etymotic ER-4B with Shure olive tips. The Seiki's have a sharp roll-off around 50-hz or so, but thankfully lacks the mid-bass hump that usually tries to compensate for this deficiency. Since these are electrostatic headphones, the roll-off was hardly surprising. The mids are an itty-bit recessed, not noticeable unless compared with the Etys. Highs are strong, but with no noticeable spikes.
The excellent speed of these headphones is obvious even at the first listen. Drums of all sorts are incredibly realistic, with a gritty "thwap" that I've never heard in any other headphone. Brass has bite, with squeals, flutters, and overblown notes all viscerally rendered. I hope that's what "speed" means at least, the faithful representation of steep wavefronts. Whatever it is, the Seiki's are textured to the point that you feel the music in a way that seems to extend beyond the ears. The 1.4-micron mylar diaphragm matches that of the Stax Lambda in thickness, but since I've never heard those headphones I can't make a meaningful comparison.
As far as imaging goes, I don't have much to compare them to. I own and have listened at length to the Alessandro MS-1000 with wooden cups and large bowl pads, but even with those I haven't had a coherent "out of head" experience. The Seikis do benefit from transparency, so that sound always seems to inhabit a realm well beyond the headphone pads, but I could never close my eyes and "see the band." Again, I can't make a sophisticated analysis of this aspect.
The textured sound, transparency, and relatively flat frequency response of these headphones let me thoroughly enjoy them with music of all genres. Although bass extension is lacking, only electric bass seems to fade to nothingness; acoustic jazz bass, concert bass, and concert bass drum all possess the higher overtones needed to still stand present. With its addictive sound, the Micro Seiki MX-1 electrostatic headphone and amp is a great listen.
Edited by peli_kan - 6/18/10 at 11:50pm