Hello,
I like MilerC’s idea of the bluetac. Many times for computer speakers I have done this or added a cut mouse pad and put it under the speaker to clean up the sound. You can take a sandwich bag and fill with sand, shot, or copper BB’s and open up the speaker and put the full bag on the Inside bottom of the speaker. You would have to do this through the plate on the back or the driver on the front. Last you can put a piece of cut foam in the port to make a more sealed enclosure, but I am not a big fan because you are changing the frequency of the speaker and you will lose bass. You can try this by putting a sock in the bass port and see if you like this sound. If you do you can then go get foam and make it look better later.
I like MilerC’s idea of the bluetac. Many times for computer speakers I have done this or added a cut mouse pad and put it under the speaker to clean up the sound. You can take a sandwich bag and fill with sand, shot, or copper BB’s and open up the speaker and put the full bag on the Inside bottom of the speaker. You would have to do this through the plate on the back or the driver on the front. Last you can put a piece of cut foam in the port to make a more sealed enclosure, but I am not a big fan because you are changing the frequency of the speaker and you will lose bass. You can try this by putting a sock in the bass port and see if you like this sound. If you do you can then go get foam and make it look better later.