[ourfpshero]

new JVC ham55x 'xtreme xplosives' headphones here. being a long time jvc fan, had to try one. 
1st, some pics: (with a fostex for size comparison)

 

 

 

 
Build: feel cheap and plasticky but sturdy, typical low end jvc, can probably handle some abuse. earpads are thick and comfy but again, feel cheap. Same with cable, feels cheap but sturdy. 
 
Looks: well, over the top, seems designed by an 11 yr old kid trying to look cool. very large for a portable. 
 
Sound: like many jvc headphones, needed a little burn-in. very ez to drive with a portable source, very 'V' shaped sound curve with emphasis on bass of course. A fun sound signature, mids a little recessed, highs a little harsh. However, a big improvement over the previous model, the HAM5X, which was just a bassy, thudding mess. 
Time and use may mellow these out, have maybe 10 hrs on them so far. 
I would rate the sound worse than the jvc ha-rx700 but better than the ha-s400
 
Conclusion: Pretty nice for the sub $50 price tag. If this has less flashy styling, I would call it a winner. 

 

[nick n]

You're the only one in here with any impressions it seems.

 
Any updates on changes to these after they have been pounded into submission? That you can recall of course. Saw you had them up for grabs, didn't take long to find a buyer

 

[ourfpshero]

they did mellow a little- i didnt do a burn in on them, just used them as normal. the harshness on the highs definitely smoothed out though

 

[Mad Max]

How do you get inside of these?  Too much reverb in the cups.
 
The cable is the same that JVC is using on those lower priced "carbon-nanotube" headphones and whatever else.  It's not all that bad, I think.  This M55X that I've got right seems to only reach down a little past 30Hz, I figured a little tinkering might get the rest of the subbass to audible levels.  So much for a bass-emphasis 'phone, lol, but it does sound like it might have some decent potential.

 

[JBal4]

Any advice on opening the 55x up?

 

[samdig900]

To open them, you have to carefully pull away one of the arms that the cans are attached to the headband with.  It is kind of difficult the first few times.  Be very careful as it is easy to snap off an arm.  Once you have detached the can, you can twist it into two pieces-- again be careful as the wire runs through the outer part and is soldered to the speaker on the inner part.  You can pull the knot away to give yourself more slack to work with.  Just today, I did the detachable cable mod on these, but broke an arm in the process.  I hope superglue fixes it!
Update: Unfortunately, super glue did not hold.  However, using a soldering iron to melt the plastic together worked, although it is not pretty.