Originally Posted by
mrspeakers 
I just tried it to be sure, and as I expected the RP2 does not work at all with the stock pads. Huge midrange hump, no top or bottom.
I had sent a note to Hennyo predicting exactly this when I found out he didn't have the O2 pads. The phone is peaky and not balanced, with a midrange boost, though Hennyo said removing the ear side phone helped with this...
For those who have the O2 pads, the first time you put them on, you'll hear a big drop in the opposite way, the mids get sucked out. The RP2 was designed to flatten this. It works pretty well with the 840, but the bass isn't as powerful as I'd like and the top doesn't sparkle, though the mids are good. I'd say the 840 is at 70% and the stock pads are not worth considering. Should be easy to fix the 840, but the stock pads won't work with this config.
So PLEASE be clear, if you don't have O2 pads, it's OK but not awesome with 840, and the stock is totally not recommended. I would really only recommend this if you have the O2 pads. The original Rastapants were tuned for the 5000 and 840 pads.
Since multiple people seem to have tried this with the 840 or stock pads, my apologies if I confused people.
EDIT: stock pads were totally in my head, 840 kind of close in. O2 deep and wide. VERY different.