So I have these cheap sony noise cancelling headphones that are close to worthless when it comes to audio quality. I decided to open them today and take a look at the internals. What I found was a large sponge covering the drivers.
I removed this sponge and also removed some tape on the back of the driver. This was a white rectangular piece of tape that opens up an airway into where the driver is. I reassembled the headphones and found an incredible increase of bass from my equalizer and a more neutral feeling without the equalizer.
If anyone else owns these headphones they should try it out and share their results.