It looks like it is the actual replacement speaker and not adhesive / poor installation as I was suspecting. The replacement parts from here are similar, but the clear tubing is a little different and seems like just bad parts from China. Let me know if anyone else is experiencing the same, but shout out to iFixit’s team for being super awesome to work with.

I’ve tried two speaker replacements so far, and each gave the distorted / buzzing sound with no bass / loudness compared to the left one. I verified this by panning audio to the left and right in system preferences. The process to take out the speaker was not that bad. I used a hair dryer with an attachment to isolate the heat to the side of the MacBook top case and keep away from the battery / board.

Any ideas what might be causing this?