I'm thinking of putting dynamat extreme behind the felt and on the driver, and a resistor in the circuit, to make my own "High Edition". 
Photo from here. I haven't opened up my HM5 yet.
Edited by kingpage - 6/18/12 at 8:28pm
Funny how people's opinions can vary. I'm a huge metal fan and I love the HM5, especially for extreme metal. I own a lot of headphones and I actually think the HM5 are one of the better cans I own for anything fast and heavy. :) Most metal recordings suffer from brickwall producten and sibilance and the HM5, for it's price, makes most metal sound just right to my ears.

Funny how people's opinions can vary. I'm a huge metal fan and I love the HM5, especially for extreme metal. I own a lot of headphones and I actually think the HM5 are one of the better cans I own for anything fast and heavy. :) Most metal recordings suffer from brickwall producten and sibilance and the HM5, for it's price, makes most metal sound just right to my ears.
I can see what you mean actually. I imagine they would help tame those aspects of a metal recording, though my previous point still stands for me. Chalk it up to personal preference I guess.
Did I really write "producten" instead of "production"? :D Damn language.
Anyway, just yesterday I sold my Grado SR225i, probably considered one of the best mid-fi heavy metal cans. It's treble was just too piercing for all the screechy black metal I listen to. Right now I enjoy the HM5, HD25-1 II and HD580 best for anything distorted.
Btw, how did you like that Uptown? I see you're selling it.

Did I really write "producten" instead of "production"? :D Damn language.
Anyway, just yesterday I sold my Grado SR225i, probably considered one of the best mid-fi heavy metal cans. It's treble was just too piercing for all the screechy black metal I listen to. Right now I enjoy the HM5, HD25-1 II and HD580 best for anything distorted.
Btw, how did you like that Uptown? I see you're selling it.
Here's a review I wrote if you want to know my thoughts in detail:
http://www.head-fi.org/t/612677/review-philips-citiscape-uptown-vs-hm5-ath-ad2000
tl;dr
I like them a lot. Much more than the HM5s in fact. :( Actually I'd rather just keep them, but I could really use the extra cash right now.
Hey , would you recommend HM5 more than Audiotechinca ath-m50 ?
I am deciding between those two
I own both (I own the identical Jaycars, that's really the way to go IMHO), and the HM5/FA-003/Lindy/Soundmagic/Jaycar Pro Monitors blow the ATH-M50s out of the water.
That's a very vague statement, and it sounds like you may not be taking personal preferences into account. Mind elaborating just a little bit?
I am not taking any personal preferences into account but my own. Sorry for not clarifying.
But I can do a quick head-to-head.
BASS:
M50s have a louder bass, whereas the HM5s bass is more pronounced and easily distinguishable. On the HM5s, I can more easily point out individual bass notes and kick drum hits, even when they are overlapping.
MIDS:
M50s have recessed mids, HM5s don't. Vocals sound a bit more intimate with the HM5s, possibly a result of panned instruments being "further away".
TREBLE:
M50 has a little bit of a treble peak, whereas the HM5s are a bit more even.
SOUNDSTAGE:
The HM5s have a very nice soundstage. Hard panned...anything...sounds like it's coming from across the room. The ATH-M50s are a bit more intimate.
BUILD QUALITY:
M50s wind hands down, but the detachable cable of the HM5s is very nice.
ACCESSORIES:
HM5 comes with a nice hard case, ATH-M50 comes with a soft case. I don't care about this and you don't either.
COST:
Jaycar Pro Monitors are $70 shipped. ATH-M50s are about $120 shipped, $110 at the cheapest.
I'm still a n00b myself, but I'd much prefer to save the $50 and get a DAC, an amp, or pay bills (you know, those things that are in Head-Fi's direct opposition).
Hi!
I own HM5's for 2 weeks. These are great headphones; when I just received them they were a bit dull and annoying, but after some burn-in they started to sound very-very good and pleasant!
But sadly burn-in also revealed channel imbalance on all frequencies ( right phone has wider soundstage and is louder than the left one ).
I checked this on different sources and double-checked with my friend on a blind test. I am very sensitive to such things and I can't just listen music with defective phones.
The problem is that I already sent my B2 IEM's to MP4Nation with exactly same problem! ( yes, I'm sure that the phones are defective and not my ears/ brain
).
So will it look strange from my side if I'll contact customer service with same reason?
Maybe there is a trick/ mod that will equal sound on both channels?
Thanks.

Hi!
I own HM5's for 2 weeks. These are great headphones; when I just received them they were a bit dull and annoying, but after some burn-in they started to sound very-very good and pleasant!
But sadly burn-in also revealed channel imbalance on all frequencies ( right phone has wider soundstage and is louder than the left one ).
I checked this on different sources and double-checked with my friend on a blind test. I am very sensitive to such things and I can't just listen music with defective phones.
The problem is that I already sent my B2 IEM's to MP4Nation with exactly same problem! ( yes, I'm sure that the phones are defective and not my ears/ brain
).
So will it look strange from my side if I'll contact customer service with same reason?
Maybe there is a trick/ mod that will equal sound on both channels?
Thanks.
Maybe you can use a balance control to try and equal them out, but honestly I would try to return or exchange them. That's not something you should have to deal with in a headphone.
Thanks for response.
I think in same way: headphones cannot be called "Studio Monitor" etc. if you get wrong instrument positioning... I'll sent back them after receive of replaced B2's.
Wow, there is even a SoundMAGIC rebrand of these?
Whoops! I think I got confused and messed up the name. I meant to say StudioSpares.
http://www.studiospares.com/headphones-studio/studiospares-m1000-headphones/invt/448760/