No, have not noticed a decrease in bass from the replacement speaker. (bought used from eBay) Not that you’d want to disassemble everything again but there does seem to be an air intake opening near the end of the long section of the speaker. Perhaps it’s clogged? Also, the shape of the inner speaker is different on the replacement - original is round and the replacement is hexagon, though they both seem to sound the same.
Thanks so much for the excellent guide! Looked up the 13” MBP guide by mistake before buying replacement speakers (that one is easy) so was kind of stunned after seeing you have to remove the system board to get to the speaker on the 15”. Luckily the guide is so well done it made a daunting task easy to follow. Thanks again!
Looks to me if your goal is to replace the thermal paste, this is as far as you need to go. Apply the new paste and begin reassembly. Here's a video showing how to apply the paste: http://www.youtube.com/watch?v=EyXLu1Ms-...