my MacBook Pro does not produce clear sound when i play music via aux or bluetooth

i have noticed recently that when i listen to music via aux(through my headph0nes or a sound system) or bluetoooth the sound is not clear. i thought that maybe my music quality wasnt good but then when i loaded the songs onto my iphone and ipad, the songs were perfectly cleat and sounded great. i have turned the equalizer on itunes off yet the sound still isnt clear. the songs sound as iff it were of low quality(the songs crack and the bass sounds awefull)

i know that the problem isnt the songs that i have. please help