Believe the customer reviews are all over the place for various reasons. 1. The M&J are efficient, so people hook them to all types of equipment. Some of that equipment is a poor match. Those components don't have the ability to control the 40mm dynamic bass driver.
2. The M&J are probably a complicated load. Most headphones are single driver dynamic. Components with higher output impedance might allow the M&J frequency response to deviate considerably. Many setups will have too much bass, others too little.
3. Break in. People pull the headphones from the box and pass judgement immediately. The M&J are complex headphones and a long break in is mandatory.
4. M&J have a relatively natural frequency response. They aren't seismic bass monsters or bright enough to cause pain. Many people want these things.
Given a chance, the GL2 and MJ2 are very nice sounding headphones.
