First of all, i am not a audiophile or very experience with high end audio but here is what i think about the Shure SRH840 ear pads on the Akg K240mkII.
I have used the Shure SRH840 ear pads for nearly a month now.
For my ears the size of the pads is slightly too small in every way. Note that i do have large ear's. At first i felt that the depth was good but slightly more would be better as i noticed my ear touching the baffle plate slightly. My first impression was that the ear pads felt surprisingly stiff but they have softened in use.
I was expecting the pad's getting very sweaty and hot, but i am surprised they actually feel quite nice and not as hot as i was expecting.
Over all i think the comfort is good. If you have small or medium ear size i think the comfort can be extremely good.
Compared to the Akg K240mkII stock ear pads the Shure SRH840 ear pads are far more comfortable, this is mainly because the shure pads have far more depth and feel slightly softer. The over all size is nearly the same actually, Akg pads are 5.5cm and the shure ( longest point ) is 6cm. the width is 5cm on the Shure pads. Akg pads are 5.5cm since they are round. I also have to say that the Shure pads feel more natural on your ear's because of the oval size. For me it helps positioning the headphones properly. I did get much better seal with the Shure SRH840 ear pads.
Both ear pads are stock.
I think the sound over all did not change much from the stock pads. There is very slight differences.
I wont really comment on the treble / mid range because its very easy fix by cutting the baffle plate cover foam from the Shure pads and placing the Akg baffle plate cover foam with the pads. But over all i did not feel there was huge difference in the sound with the stock pads so i kept the Shure SRH840 as stock.
Bass is where the noticeable difference is, especially in the sub bass region. There is not huge amount of more sub bass but enough to notice a difference.
With the Akg K240 stock pads i always felt it lacked extension in the sub bass region.
Over all i think the sound is fairly good on the Akg K240mkII with the Shure SRH840 ear pads maybe slightly more refined and separation is better. They do make the Akg sound warmer/fuller and maybe slightly darker as stock but this is fixed by replacing the baffle plate cover foams.
I recommend trying them if you have issues with the stock pads.
Edited by Notus - 5/24/14 at 3:22am