The sound you ear is a distorsion.
it grows when you lower the frequency because it’s ringing the structure of the speaker with the mac structure.
If you have too much adhesive tape between the speaker and its “cabinet” you will have distorsion
if you have a semi contact between the speaker and its cabinet you will have distorsion too.
I replaced mine because of the same issue you had (and obviously I know that will happen again sadly)
I had this blown sound on my replaced left speaker too, I fixed it again.
You have too keep the best way you can the original adhesive on the mac structure when you leave the speaker.
You can manage it to keep this really really thin adhesive surface at the same place it was originally.
After that you just put the new speaker and press it in its cabinet… but really press it a LOT !!!!
to have the best contact between the speaker and the structure.
Before doing anything you can try with a sound: just play on the new speaker a sound like low voice (you will ear better this distorsion with low medium frequency than very low frequency)
and just press on the speaker, the distorsion will disapear.
Of course don’t press directly on the “sub” speaker. Just press the plastic structure of the speaker.