DIY electrostatic headphones

[spritzer]

I did search but I couldn't find a dedicated thread about DIY electrostatics so in the spirit of getting the discussion started, here is something I've been working on.    Well over a decade ago I bought up all the spare Sennheiser HE60 parts to assemble new headphones.  The first thing to go out of stock was the main housing so to assemble the last pair, I had to adept a HD650 housing to take the HE60 drivers.  Ever since then it has stuck in my head to make my own drivers for those housings and well... here is version 2.0:  

I bought a ratty old HD650 and completely stripped it apart.  Headpad, earpads and cable went into the trash while the rest went for a long bath.  First step is to make the baffle flat so a lot of cutting with nice, sharp, flush cutters.  I naturally forgot to take a picture of that step...  Next step was to fully measure what area I had to work with and design PCB's to match that, while maximizing the open area.  The end result is three different PCB's, as they are all setup to be dual sided.  One for the stators, one which holds the diaphragm and finally the simple outline which holds the dust covers and can act as a spacer.  Some pics of them assembled in the housing:

Four nylon screws hold the sandwich together, fixed with PEEK nuts to get extra gripping power as the assembly had to be as flat as is possible.  Dust covers placed away from the stators so they don't cause any issues.  Earpad side:

Due to the screws, some earpad mountings have to be cut up to get the pads to fit but yeah, they are just cheap crap from China so who cares.  I could cut a slot in them to try and make it fit but maintaining as much pressure on the drivers as I can is far more important. 

Final assembly with a King Sound cable as I have a couple of those sitting around.  For the diaphragm I used my usual stock of 1.4um film and the earpads are just the cheapest leather pads I found on ebay.  I have a couple of nicer ones but these are the thickest and that helps make them more balanced sounding.  The diaphragms were stretched by hand on a mirror (which is my preferred way) and glued with wood glue (thanks for the tip Aumkar!) which is just perfect for this.  Coating is anti-static spray which means they energize in five seconds or so which I can live with. 

Now for the sound... pretty damn good for something so simple and literally being the second set I assemble.  Well that and zero effort has been put into sealing the baffle or just any sealing at all.  I just stuck the PCB's onto the baffle and built up the stack.    Overall sound signature is similar to the HE60 but not as diffused and with far more bass output.  Maybe a tad too much at times as there are some oscillations that I can pickup at very high volume levels and under high excursion.  I tend to go with slightly less tension on the diaphragm so that might be it.  Treble is very pronounced with the thinner pads but with the ones pictured, it is just perfect.  These are not forward at all and the soundstage is excellent for this size of a driver and non-angled earpads.  Sensitivity is slightly lower than the regular Stax sets but still only marginally so.  All in I'm very happy with the roughly 150$ outlay for these. 

Now this is version 2.0 but the first version used a HD58X from Drop, brand new in the box that I cut up.  Same driver profile but thicker stators so the efficiency was really bad plus the stators had full solder mask on them.  Now I'm out of the spacer PCB's for the dust covers so next time I order PCB's, I'll make another set.  I also have some diaphragm spacers which would work well for normal bias as I've always wanted to mess more with that. 

[chinsettawong]

Very nice!  How do you stretch the diaphragm by hand?  Do you have a scale or something to help you tension each side of the diaphragm to the same tension?

[spritzer]

I take a large piece of mylar and do it all by hand.  I can get good repeatability but I often stretch 10 diaphragms at a time this way so it's easy to match them into pairs. 

[swt61]

Pretty damned impressive Birgir!

[spritzer]

Thanks.   

[Guest]

they look great