Restoring a Micro Seiki MX-1 electrostat - source for material an thickness?

[Agnostic]

Some years ago I bought a Micro Seiki MX-1 with energizer. The problem with those is that the material that was originally used for the diaphragms deteriorates. As a result it is impossible to find a pair that still works unless the diaphragms have been replaced. The pair that I bought had a new pair of diaphragms but they were not mounted correctly so I finished the job and got them to work. The problem with them is that because of incorrect mounting of the membrane on one of the mounting rings, which has insufficient tension, one of the two sides has a bit less volume and sounds a little less dynamic. Despite that fact they are still a pleasure to listen to. They sound fast, have non of the sibilance issues I have with my Stax Lambda and have some of the deepest and tightest bass I have ever heard from a headphone and generally sound very musical. Because they sound so good I have always had the idea in the back of my head that one day I would try to find a second pair and do a proper job of repairing them. A few days ago someone offered me another MX-1 for free.

Now for the questions: I have no idea what the thickness of the membranes on my first set is and I would like to try to get as close to that as possible. I know that the Lambda has 2 micron membranes and that it sounds a little harsh in the treble as well as suffering from sibilance so I am guessing I should go up to at least 3 micron, though on the other hand the micro Seiki has much smaller diaphragms which may also affect the sound. Any thoughts on this?

And question number two, does anyone know where to get thin Hostaphan-RE or Mylar-C in Europe? I have found 6 micron and possibly some 4 micron but nothing thinner.

[mypasswordis]

I haven't ever had sibilance issues with the SR-Lambda. Why exactly can't you remount and re-tension the diaphragm in the first pair? If it's because you can't tension it the exact same amount on both sides, then that's a problem. And are you trying to replace the diaphragms on the second pair or the first, or both?

As to thickness, iirc going from SR-5 to SR-5NB, Stax decreased the thickness of the diaphragm in the circular driver they were using, which increased the bass. And all the newer Lambdas use even thinner diaphragms, like 1.35 um.

[Agnostic]

I thought about a repair of the first pair but I didn't get around to it, partly because I enjoyed them too much and they are quite difficult to assemble correctly once you take them apart because the construction is very fiddly and partly because back then I didn't find any source for thin mebrane material.

The reason my Lambda sounds sibilant probably has to do with the amps I'm using, but I have to make choices, I'm also an avid photographer and most of my money goes into that so I can't afford getting an expensive dedicated amp for it. Anyway, aside form the problem I mentioned the Micro Seiki sounds much better to me than the Lambda, I prefer my headphones more to the warm and musical side and that's what the MX-1 provides.

So what you are saying is that for the best bass I should use the thinnest membrane I can get? The guy who gave me the second MX-1 had a home built stat which used 0.95 micron mebranes mounted in an old Audio Technica frame. The sounded nice but didn't have much prat. In fact they sounded a bit laid back for my taste, almost Sennheiser like. Now admittedly that may have had more to do with his amp, a huge home built tube amp or with the fact that he tensioned the mebranes very tightly, or with the fact that he used stators which were curved. On the other hand I like the sound I get from the first MX-1 and I'm pretty sure those mebranes are thicker than 1.35 micron...

Equal tensioning between the two drivers should not be a problem, I learned a neat trick for that, which involves tapping the first diaphragm and recording the tone it produces and then tuning the second to that tone.

[mypasswordis]

Interesting choice, using curved stators. I wonder why though, for the purposes of a headphone in which the driver is sitting right next to the ear dispersion shouldn't be a problem. Of course curved stators create odd problems with tension unlike as you said, he uses a large amount of tension. In which the bass disappears. 0.95 definitely seems on the thin side, though apparently the HE Audio Jade uses 0.5? I'm definitely going to have to defer to spritzer, who knows everything there is to know about electrostatic headphones, but otherwise say 2-4 microns is a safe bet, with something closer to 2 being preferable. spritzer would also know about where to buy mylar in Europe.

This person used 1.4 micron: http://www.head-fi.org/forum/thread/498095/review-refurbished-micro-seiki-mx-1-electrostatic-headphones-ms-2-headphones-mp-1-amplifier

[Agnostic]

Thanks, I sent Spritzer a pm. In fact he helped me with some advice on the first pair.

The guy who built the stats said he used the curved stators to allow the diaphragms to push more air, though I wonder if a curved stator with a very tight membrane might in fact not end up pushing less air. Might be an explanation why they sounded so laid back for electrostats? He was also using a very high bias voltage, 1200 volts if I remember correctly.

Edited June 28, 2010 by Agnostic

[mypasswordis]

I think curved stators would indeed cause the diaphragm to have less swing capability and thus not be able to push as much air, all things else being the same. Maybe that's why at 1200 volts he's not having issues with too small a D/S gap, unless he changed the D/S gap to be bigger as well. What material is he using for the stators, do you know?

[spritzer]

I have no idea where to get mylar this thin in Europe but I got mine from the US. There is a thread on DIY headphones over on HF running now which has a link to the store.

The stock headphone didn't have mylar to begin with but it was relatively thick. In that time 3-4um was the norm as thinner material wasn't available.

As for curved stators, they are a stupid idea, even the inventor of curved panels has said so. Now staggered panels, that's a whole other thing and quite a good idea.

[mypasswordis]

Martin Logans FTMFL

[spritzer]

They do look pretty on TV...

[mypasswordis]

I personally think they look hideous. Like some sort of air filtration/ionization machine.

And the smaller ones look like that ugly llama gif thing:

[wualta]

Didn't we find that Micro Seiki (or its OEM) used polyurethane diaphragms, as Koss used in the ESP-9?

The smaller Martin-Logans look to me like some chairs designed by Charles Rennie Mackintosh.

[mypasswordis]

That's what that guy on HF who repaired his said it was. But there are way more functional (well, sort of. after a good cleaning out of the disintegrated foams) ESP9s than MX-1s out there.

[Agnostic]

Thanks for the input Birgir. Do you have any ideas on what influence membrane thickness has on the sound?

I wrote to Mitsubishi plastics in Germany who used to produce Hostaphan to ask them for a sample but alas they stopped production of the very thin types but after a lot of searching yesterday I managed to order some 2 micron Mylar from a site in the UK that sells parts for building model airplanes.

[Agnostic]

Didn't we find that Micro Seiki (or its OEM) used polyurethane diaphragms, as Koss used in the ESP-9?

That’s what I understood. When I disassembled my first pair of MX-1 I found broken pieces of a milky white material which felt a bit rubbery. It had so badly deteriorated that it almost fell to pieces when you touched it.

@Spritzer: Thanks for the mention of the HF thread. When I finish restoring the MX-1 (I am thinking of doing both and perhaps trying two different thicknesses of membrane), I may give building a stat from scratch a go. I still have an empty DT990 shell lying around which I could use as a frame. I guess that would be a Beyerstatic then

Edited June 29, 2010 by Agnostic

[spritzer]

Didn't we find that Micro Seiki (or its OEM) used polyurethane diaphragms, as Koss used in the ESP-9?

Yup. Not entirely sure why they used that instead of mylar since polyurethane's big selling point when used in grocery bags is that it will break down with time...

Thanks for the input Birgir. Do you have any ideas on what influence membrane thickness has on the sound?

The key here is really mass as the electrostatic force is so weak. To get the speed a modern model can do you need to either use a thinner membrane or use extreme tension and thicker material. The latter solution has many issues though as you kill the bass amongst other things.

I still have an empty DT990 shell lying around which I could use as a frame. I guess that would be a Beyerstatic then

That would be the ET990 to compliment the real Beyer 'stat, the ET1000.

[mypasswordis]

Damn straight, even if it's the best thing ever, it will still be 10 less than the ET1000. I'm going to try removing the felt I put on the backs of the cups, I think they're making the sound too closed in. Also I think the wires connected to the stators are insulated but maybe I should further insulate.

[spritzer]

Insulation is your friend with this stuff.

[peli_kan]

I recently fixed and have listened at length to a pair of these.

Review: Refurbished Micro Seiki MX-1 Electrostatic Headphones (MS-2 headphones & MP-1 amplifier) - Head-Fi.org Community

I used 1.4 micron mylar stretched super tight, and the bass rolls off quite a bit. I'm not sure if Turner Toys would ship mylar to Europe, perhaps you could ask?

[mypasswordis]

Hey, speak of the devil! 1.4um is pretty damn close to what Stax are using, how about trying to use less tension? That, or the Micro Seiki pads aren't sealing properly.

[Agnostic]

I recently fixed and have listened at length to a pair of these.

Review: Refurbished Micro Seiki MX-1 Electrostatic Headphones (MS-2 headphones & MP-1 amplifier) - Head-Fi.org Community

I used 1.4 micron mylar stretched super tight, and the bass rolls off quite a bit. I'm not sure if Turner Toys would ship mylar to Europe, perhaps you could ask?

Thank you for the reply. I saw your thread when I was looking around for info. The information is very useful. It seems that stretching the mylar very tight really affects the bass and even the mids a little, since my first pair doesn't have very tight membranes yet produces some of the deepest bass I have heard in a headphone. I also haven't noticed any recessed mids and I'm quite allergic to those.

I have the same out of head experience with the seikis that you describe. In fact on some occassions I have taken them off to check whether I hadn't accidentally left the speakers on while I listened to them because they sounded so transparent. If I can match both diaphragms of the second pair to the good one in my first pair I am going to be very happy with them, and for my taste I think they might become my favourite headphone out of the ones that I have heard or owned. They will certainly be the most natural and musical sounding.

I suspect my first pair uses 3 micron so I think i will go with the 2 micron mylar I ordered and tighten it just enough to keep the mylar flat on the mounting ring. Just waiting for the mylar to arrive now.

[peli_kan]

Coolios, good luck with your rebuild.

Indeed, I likely overdid the tensioning on the diaphragms. I'm sure that they'll loosen over time though, since 1.4-micron mylar quickly goes into plastic deformation when subject to even moderate force.

I hope to hear how the Seikis compare to your lambdas, since I've read that they're comparable. My nooblet ears are still sailing through the multiverses of different headphone setups, and more often than not I have to listen vicariously.