Re: sound changes.
First off, I want to say that I do not have the original/stock HF-2s to compare to, so all my opinions are based on memory and feel from the stock HF-2 form. I was not able to A/B them side by side.
Also, my gear is only very modest.
Source: Macbook aluminum -> uDAC -> Little DOT I+ -> Woodied walnut HF-2
Although this woodfying process only had a brief stunt, the sound definitely became airier than the original from what I remember. This could be due to its extra length in the chamber of the wooden housing, but there is without a doubt, a more airy presence in every song. Is this a good/bad thing? Well, it actually bothered me on some songs, and not on others. Some songs requires more of an intimate feel, and the airiness makes you feel like you're in a concert hall with some sort of slight wind/air/echo that goes a long with that type of venue.
On the other hand, with songs that require more of an airy tone, it was excellent. Note that this does not mean a soundstage increase, the music simply feels to have more space when they resonate. Additionally, the mids seem VERY slightly less forward after the change. I cannot confirm this notion though. Also, for instruments that have more of an organic tone (ie string instruments like cello etc.) sound more organic to me. There seem to be a tint of metallic sound to the stock cups. It's similar in a way that when you drink coke/any other soft drinks out of cans vs glass bottles. Glass bottle coke just tastes....more like coke without the metallic flavor. In the similar sense, the music sounds more 'right' especially with violins/cellos etc.
Last but not least, the headphones became MUCH lighter to wear, and hence much more comfortable. Bowls that used to bother me with my sensitive ears are not as bothersome. I can wear these for much longer periods vs stock form.
I have to say though, they don't feel like HF-2s anymore after you take away those aluminium cups. I do miss that and stare at the aluminium once in a while.
But now the process has taken a step further and are now turned to v.3 Vixen Cocobolo wood via Larry.