Fostex TH-610 Lawton Mod
I finally received my Fostex TH-610 for the mod.
It took me longer than I had anticipated to decide on which model Fostex to use for the mod. The TH-900 mk2 has the more powerful 1.5 Tesla magnet structure which translates to roughly more of everything sonically. That’s quite appealing, but the $1599 MSRP wasn’t. Since it’s a project on a headphone I’ve never heard (crazy, huh?), I decided to go with the much more affordable TH-610 with its 1(+) Tesla drivers.
The TH-610 is a more neutrally tuned Foster driver headphone. When I first received the 610 I was pleasantly surprised by it’s sound. Very resolving, with a wide sweeping, U-shaped sound. Just a touch of brightness. Boy do these have detail… I’d say more so than my previous detail-king Focal Clear (which are an excellent headphone).
The 610 paired wonderfully with the Chord Hugo TT2 I have on hand (thanks to a loaner program of which I was invited by fellow forum member @jb77- thanks Jeremy!). It really revealed the capabilities of both devices.
I had planned to keep them stock while I listened over the weekend so I would have a better sense of the changes made by modding them, but after a few hours of listening, I just couldn’t handle the tiny ear pads. My large ears were crammed into the small opening for far too long even though I was enjoying the sound, it was too uncomfortable to continue. I decided to swap the pads out for the ZMF Ori Lambskins. I also added Dekoni made attenuation rings designed for Fostex TH-610/TR-X00 (the Massdrop variants using the same drivers).
Man are the ZMF pads comfortable! I was able to continue listening without any discomfort, and with little change to the sound.
So today I wake up deciding to completely forgo my original plan since I already began to mod them the night before (pad swapping is a mod, right?).
Here are the photos I took during the mod. You can find similar photos on Mark Lawton’s website as that’s the only place to find instructions.
For the full mod you will need: Fostex TH900/TH610, Lawton Tune-Up kit, Lawton Custom Wood Chambers (cups), Lawton pads (I opted for ZMF based on their reputation and advice from members of various forums), and a Phillips screwdriver.
The Tune-Up kit consists of self adhesive strips that are essentially placed on the hard plastic surfaces of the driver housing/assembly. They are intended to reduce resonances in the driver chamber.
When you remove the pads this is what you’ll see underneath.
The stock cup removed. You can see the ‘gauze’ styled anti-resonance material.
The backside of the driver is exposed once you remove the stock cups.
This is where you apply the Tune-Up kit.
Here you can see the Tune-Up kit applied to the back of the driver.
For the TH-610 the kit consists of 3 pieces per driver.
This is where you add the most expensive Lawton component, and what I now affectionately call the “Boom-Room”.
You’ll notice that the Lawton Chamber uses a different style anti-resonance material compared to the stock cups.
After what amounted to about an hours worth of work (give or take a few minutes), you now have a completely modded Fostex TH-610!
Easy-peezy, lemon squeezy.
Shout out to my son whos desk I used for the mod.
Semi-Quick Take
It’s mostly what I initially heard in stock form. The highs have been slightly tamed, and there’s a little better separation. The soundstage which was already fairly wide for a closed-back (sort of) is now my own private little studio. Isolation stayed the same which wasn’t the best given that these aren’t a true closed-back.
Now the bass is another story. These Foster BioDyna drivers have excellent extension in both directions. To a point where if not implemented properly they can be too bright and too boomy.
What the Lawton Chambers essentially did was to create a subwoofer like enclosure that allowed the driver to really shine. It’s not boomy (don’t use any attenuation rings, it’ll make these unpleasant, and sloppy BassCanons). It’s present and very well extended.
I still need to further explore pads. I find the Ori’s to be to small for the better breathing updated drivers. I also think that I’ll benefit with a shallower pad. I’ll update when I receive new pads and add more photos.
With the combination of the Tune-Up and the Lawton Chambers I’m left with a better version of what the 610 was in stock form.
Was it worth it?
For me it was. 
-Christopher