Powerbeats Pro-No Bass?! Help!

Hello,

I've had the Powerbeats Pro's since they released and they've always sounded great. However last week, i was mid workout and all off a sudden, mid-song, it seemed like the bass really kicked in and the audio got a bit clearer. I thought this was strange. It was a noticeable difference, especially in the bass. I finished the workout and the next day I tried them again and they were back to how they were before, still good audio, just not as much bass as the day before. It got me thinking maybe my pair is defective or something. Took them to Apple, they sent to service center and they sent back saying 'repaired' but I still am not getting that sound quality that kicked in during that one workout. And all the reviews i've read say that these headphones are 'bass-heavy' so I still feel like mine might be defective.

I don't know anyone who has another pair of these. Those that do have them, are they in fact bass heavy?

Any help appreciated!