The Panasonic RP-HTF600-S headphones I bought sounded dull and bass boomey. Also the detail in stereo background imaging detail is completely lost(the air around reverbs and vocals etc.) Months later after thorough break in period at reasonable volume levels(not screaming loud levels) the Panasonic headphone started to phase in and out on the left side speaker driver, the sound would come and go and the treble was lost after that too. Now it sounds like crap and is hard to listen to.(a high ear fatigue even at mid volume levels.) I don't know if I got a defective headphone but these Panasonic's I am not impressed with at all. They are comfortable enough, but the 50mm speaker drivers are crappy sounding, unbalanced and crappily made as well. Is that even a word ?
On the other hand I bought the JVC HARX700 headphones and they sound a 100 times better than the Panasonic's even before break in, especially in the clarity, stereo imaging, and perfect low to high balanced sound. Both 50mm speaker drivers are perfectly matched in sound quality, unlike the Panasonic. I like the JVC's even better than all my Sony Studio Monitor headphones too.. No sound frequencies are missing on the JVC's, very clear and un-boomey sound, unlike the Panasonic and Sony and many other brands of headphones. The JVC"s sound fantastic, and very neutral, and are better made than most headphones even in the $300 and down category and even more comfortable than most headphones. But the JVC's are big headphones, however the sound quality makes up for their huge size.