The more I listen to the stock T50RPs, the less happy I am with them.  I was positive at first, but they have the sound of speakers in a room with terrible acoustics to me.  It sounds like the high-end is completely shaved off (lacks the cleanness in the highs that I'm used to hearing from the SR225i), but I do like the mids of the stock T50RP.

I've heard headphones with similar acoustic properties of the stock T50RP.  The weird thing about the T50RP is that I can hear cleanness in the mids, whereas those cheap headphone alternatives tend to just sound smeared and imprecise overall.  The problem is that the lack of cleanness in the highs and the weird things happening in the lows are becoming more and more distracting to me.

It was probably the different color on the headband rods that contributed to the change.

LOL.  Eleysian, you should think of the T50rp as a headphone you pulled off the production block before it was finished.  They stuck the drivers in there, but they hadn't put the damping in the cups yet. 

If you heard my T50rp's and a stock pair blindfolded you would think they were completely different headphones.  Damping is incredibly important with orthos, especially a closed ortho and even more especially a closed ortho with a driver like the T50rp which really needs to be slapped into submission.  I can't emphasize the idea enough that the stock T50rp is an unfinished headphone.  Think of it as you would think of an amp that is missing some vital peice.  Or a Porche if you put Prius suspension on it.  It would be hard to judge the Porche's handling potential with that crappy suspension. 

The echo you're hearing is directly caused by the lack of damping. 

But damping doesn't just reduce cup resonance.  It changes the way the driver behaves, changes the speed and frequency response.  A well damped T50rp's driver is operating differently than a stock T50rp's driver.  Regardless of cup resonance. 

hans: I received my T50RPs in July, so unless they were a set that's been sitting on the stockroom for awhile, I'd imagine they are a relatively recent production run.

RD: Does the dampening help significantly with that weird echo (it's not really an echo, but it just sounds way too boomy in a bad way, like when virtualization audio 3D mode is turned way too high)?  I like the mids but I wish there was more crispness in the highs and a tighter lower end.  Can mods really make that much of a difference, or do the mods only help with the weird echo?

just throw in some fiberglass(r-19 value is fine) or mineral wool(roxual is good stuff) and polyfill/fiberfill and see for yourself. pads make very nice difference too cause  how it couples to the ear. i liked using akg 240 pads and the shure 840 pads. the felt/cloth on the shure 840 helps good amount as well but i found the 240 foam discs found in the 240 studios work great too. it fit inside the shure pads fine. the pads alone can make a nice change cause how horrible the stock pads are and how close the drivers are to the ears.