I bought some JVC headphones that are high quality and the sound is really clear after a while i notice when i plug them in my Sensation the sound is terrible it sounds like a pair of 5 dollar headphones with no bass, it was working fine what gives?
Wait... So you were using the headphones in Sensation fine for some time, but then this suddenly happened? Try them in another device to see if it's a problem with headphones. You can also turn on SRS/Equalizer in Music settings.
Did the sound get worse after answering a call and going back to the music app? Does the problem get fixed when you reboot the phone? If so, disconnect the headphone, play music through the speaker and connect the headphone back while the music is playing. It should get fixed. If you have a headset, while listening to music, you can press the main button twice (as to redial a call) and then immediately cancel the call. It should give you back the good sound.