brother, this can be used for Bass sound fine tune, pls refer to your speaker manual for details. in general, put 海綿 into speaker can put down the Bass sound. So, if u feel the Bass sound is much then your expectation (e.g. u feel BOOM), u can put 海綿 to put down the Bass
I am also a new hand in HiFi, just play ~1/2 year.
I learn this from my speaker manual only. Yep, put 海綿 will 減低個 Bass. So, just put it IF u feel BOOM BOOM. U can test it with same CD & volume level to see which Bass condition is good for u.
Hope can share more HiFi info. together from now on