New headphones too much bass.

Hi there,

I recently bought three pairs of these Headphones.

I absolutely love them, (save for the cord, which I just shorten) I've been with the same model for years.

Anyhow, I now have three pairs and tested them.

It seems one pair is incredibly bass heavy compared to the others.

How can I fix this?

(Music played from iPhone, all same source, no alterations on any headphones, they are all 100% stock, inline volume at 100%.)