This thread is FREAKING awesome! Great job BMF!
I received my T50RP and 840 pads today and did about an hour of burn in before giving them a listen. Not terrible out of the box, but definitely a bit dark, muddy, veiled with a tad of distortion on the top.
I took them apart and discovered the top ports were already taped off from the factory. The bottom ports were completely covered with a very thin layer of felt. The back of the driver had a pre-installed square of transpose membrane. I left all of this intact.
I used ordinary materials laying around the house to do the mod, namely, Home Depot plumbers putty to fill all of the baffles and holes, some Pergo flooring foam underlay (thin) for the cup backing, and cotton balls (pulled apart to avoid density problems) for the cup filler.
I'll most likely switch out the putty but wanted to test how well it will hold up. Edit: My putty is oil based so it won't dry out.
I probably ended up closest to the #37 mod.
Total cost was $74 for phones, $15 for 840 pads, $9 shipping an $0.20 in materials.
THESE PHONES KICK SOME SERIOUS BOOTY FOR LESS THAN A BENJAMIN AND 1-1/2 HOURS OF TIME!
I'm burning them in with Steely Dan SACD stereo layer now and will run pink noise through them for a while when not listening.
They are just slightly darker than my HE-400 but really unbelievable sounding though my OTL tube amp. They seem to drive about the same as HE-400.
Edit: The front of the driver face had some thin layers of felt. I peeled off the top felt layer and then cut the felt square out to expose the driver. It helped to brighten up the sound a bit and lift the veil off of the whole spectrum. This was an excellent result for me, bringing it closer to the HE-400. What is amazing is the treble control, there is no hint of sibilance.The phones seem to have a bit more detail retrieval this way. The HE-400 is this way. Only the mesh from the pads covers the driver face.
Ortho's are great, modded T50RP ortho's are awesome! Thanks for putting together such an informative thread. Can't wait to get 100+ hours on these.