OK I am a happy (Easter) bunny. My woodied T50's are finished and I am more than happy with the sound with very little in the way of modding. Here is how I did my conversion. Pictures may follow when I figure out how to post them!
Wanting to utilize the current plastic baffles I decided to make an oval pair of cups. I only had some 2.5 inch square cherry wood lying around so I cut two pieces to the correct length of just over 4.25 inches, sliced them in half and edge glued them together to make two pieces of 5x4.25x1.7. I put these on the lathe using a screw chuck and turned the face, reversed the wood on the screw chuck and turned the cup using Smeggy's useful dimensions. Yes there is a hole through the centre of the cup but this is removed in the next step. To make the oval cups the centre 1/2 inch of the cups is sawn out and the half cups reglued to give the oval of the correct size.
At this point, having made two oval cups I found the original Fostex baffles have a lot of strengthening ribs which get in the way. I decided to ditch the original baffles so a quick look through the spare timber pile and some 3/8 MDF got cut to size and pressed into service. I removed the headphone drivers from the baffle and having cut a square hole screwed the drivers into place against the MDF after using some Newplast to seal the driver against the MDF. I put Paxmate on the back of the cups and used a ring of Paxmate around the edge of the baffle to seal the baffle against the cups.
I did a very simple rewiring job using wire connectors, no soldering, no hassle. I assume it can't work any worse than Fostex's awful TRS (jack plug) job. I also use the original headband screw into the new wooden ear cups. It only needs a 10.5mm hole drilled throughout the centre of the cups and then a little work with a countersink bit and the original screw fitting screws into the headband end plate really easily. There isn't a lot of movement but I find it isn't necessary to move the ear cups much. You need to remove the anti rotation pins in the headband endplate. I filed these down and used a square of Paxmate between the wooden cups and endplate. Even if I made round cups and didn't cut out the centre I would have been able to use the hole in the cups (from the screw chuck) for the headband mounting. There is no need to buy an expensive chuck to make cups for your Fostex.
Apart from Paxmate in the cups, and Paxmate to seal the baffle to the cups, the only dampening used is the Newplast seal (and maybe a little incidental mass loading) between the drivers and the MDF baffle and some Dynamat around the edges of the driver. The bass breather hole in the cups is 2mm diameter and the breather hole from back of the driver through the baffle is also 2mm diameter. The cups were finished with several coats of car lacquer and I use Shure 840 ear pads to finish off. Recabled with a jack extension cable I had lying around, I just cut off the socket end - next time I'll do a better job with some proper cable.
Using an O2 amplifier the volume needs turning up as the efficiency seems quite poor but the sound is nothing short of astonishing. Bass is tight and extended, treble is sparkly and detailed. Mids are beautiful, female jazz vocal is alive. I hear when acoustic bass notes start and stop, I'm sure I never heard this amount of detail before from my Denon D7000's. I have another pair of T50's I have been fiddling with for ages and still don't think I have the sound right. Even classical sounds sparkly. Compared to the Denons the tonality is also better, the sound has more body to it. To be honest I can't believe I have achieved so much just by woodying my T50's, in fact thinking you can't 'polish a turd' I nearly sold them a few days after purchase. With the O2 the silences are incredibly black, just me and the sound of blood rushing around in my ears (and maybe a little tinnitus lol). I think this accounts for some of the extra detail I am picking up. I'm glad I have persevered with these cans. If anything needs work it is the sound of the piano that needs tuning, but I think that applies to all the headphones I have heard.
Sad to say I promised this conversion to my son for his birthday in a few days time.... sigh! I will do my other pair soon - I hope this wasn't beginners luck and my other pair turn out to be as good.
