Rip the cd to a losslike format like aiff, wav or flac then play it back with your phone

Perhaps try loosely folding a small towel until it is 4 layers thick and sit the speaker on that as an experiment? You could also try placing the speaker in different locations.

You would need to discinnect the existing tweeters in the speakers youre adding this to, not sure if the unit has a crossover inbuilt. If it does then just connect in parallel to existing input on speakers youre augmenting, if not then you will need some sort of crossover arrangement which could be as simple as a single capacitor in series with the unit