so i replace my stock stereo with a alpine cde-137bt single din and used the wire harness adapter for the stock amp and sub and it sounded good at first but after i replace my battery it sounds like it doesn't bump as much as it use to,

Any ideas on settings for the aftermarket stereo? or is my amp going out? i can hear and feel bass from the sub when i put my hand over it but doesn't sound as loud.....

 

hmmh. Check the body to the battery ground.

Check the radio head unit for 'loudness' or some other bass volume feature and for output levels. I would re-read the manual for settings that were wiped out. I do not belive it is the amp/wiring adapter...

Could the amp or the speaker be failing? Possible - but check the other stuff first.