Fostex TH900 open back mod (ongoing)

As title, removed the stock cups and attached some...plastic enclosure on the baffle



Along with some rotating of the internal foam according to the HF TH900 mod thread: http://www.head-fi.org/t/802704/th-...denon-more-bass-mid-soundstage-smooth-trebles, so far, bass is absurdly brutal but surprisingly clean given the lack of damping, the lower mid dip that causes male vocals to be hollow appears to be gone, unfortunately, the treble peaks are still present, picking up sibilance easily.

Next step: fixing/taming the treble.

Update (8/16/2016): Experimented with putting TP over the driver grill, putting 2-ply TP kills nearly all the treble and makes these dark as hell, while 1-ply helps mitigate some of the edge without killing too much treble air, I am liking this quite a bit...

 

TH900 open back mod: 2nd Chapter - Felt and more felt.

For a more permanent solution (also to eliminate audible TP flapping), I purchased some Felt and plan to use it to replace the TP, despite it being much thicker, putting in front of the driver grills appears to have a milder effect on treble attenuation than the TP. 1-layer in front of the grills doesn't do much at all, while 2 layers appears to have a similar effect of one ply of TP. Need to try some back damping on the enclosure....

UPDATE: Adding Felt layers in front of the driver grills is decently effective at curing treble peakage, and also appears to tone down the bass, or mitigate a good amount of lingering rumble.

 

Whoa, this seems really cool. I wonder what would doing this on a th600 do. They have much nastier treble as far as I know, and don't quite reach the same level of bass as the th900. 2ply tp and rotation of it's internal foam might bring interesting results...