So I was doing some cleaning in the storage room and I dug out my old Panasonic (in the original box which I packed) from a box of random stuffs.
It has been in the storage room for the last ...8 years? I bought it around 1999, and had to put it into storage due to the cracking of one of the plastic ring that seal the gap b/w the driver and enclosure (wasn't really know how to fix stuff back then..young

). I tested it and surprisingly it still sound as good as the day I packed it in, so I cut up a pair of my 'other' old Panasonic (different model) and mod a new set of plastic rings to fix the old problem.
RP-HV600 is considered by many (including myself)
THE best earbud model Panasonic has ever made and a strong competition to the original Sony MDR-E888 (Japan) . Sadly the production stopped at year 2000 and Panasonic has become (almost) a bottom feeder ever since - producing the crappy stuff for the mass.
Copied this from a site (no longer exist):
2-Way Drive technology for excellent midrange and high frequency response with a powerful bass (15mm / 9/16"" dome type driver and 11mm / 7/16"" vibration plate).
- Super round ergonomic design.
- Samarium-cobalt magnet for high quality sound.
- Sound Control (SC) switches between reference and XBSr extra bass modes.
- Twist free cord.
- Compact carrying case.
The overall sound: Great high + mid + Sound stage + detail. Tight bass.
So don't say Panasonic never make good earbud, they just don't do it anymore...