PAD FELT MOD:
I have already talked a bit about using different materials inserted inside Hifiman pleather (or velour) pads to further smoothen HE-4's treble response... And I really enjoyed the way rug pad worked with Sennheiser HD800 - it lessened resonances inside cup chamber without decreasing airiness and imaging too much. See the physical difference between it and typical 2mm felt:
Rug pad was nice with HD800... But HE-4 may need something more dense. Therefore I decided to try this approach with the felt itself... I wanted to achieve smoothening without decreasing imaging, sense of openness and level of airiness too much (which may be the case with a non-perforated felt).
How to do it?
Here is an image how it can look like (above is a non-perforated, below is a perforated version):
Insert one circle inside OR underneath each pad. Inside means INSIDE the pads - it will hold there by friction. Underneath means in between pad and driver - it will hold there because it won't have a chance to move at all.
How does it effect sound?
I must say that it works as expected... Slightly decreased air as well as smoother treble response but the quality of imaging remained the same - or even very slightly improved due to less airy/more black background. Slightly cavernous timbre of the pleather pads is fixed. Sense of openness is a bit decreased, perceived soundstage width also slightly (but you cannot have everything). This mod works best IMHO when inserted underneath the pads (not inside the pads as I was using the felt before) but you could always try to insert it inside as well for slightly different effect on the overall sound. Description of slight tonal improvements follows...
"Especially focusing on both male and female vocals, I found that while both pleather and velour pads gives similarly nice male vocals (a bit different but similarly fine), female vocals are significantly less natural with velours (more sibilance, less natural tonality). With pleather pads, I would say that both male and female vocals were sufficiently natural but the felt (insterted inside/underneath the pads) improved on that appreciably - it basically made both male and female vocals a bit more full and somewhat "shifted" sibilance in a way that it's pronounced in a more natural way (there is still some slight sibilance but now more authentic/natural-sounding)."
I would like to encourage anyone to experiment a bit with the mod - try to use perforated or non-perforated felt, insert it inside or underneath the pleather pads - to find the best configuration. And, in the end, it may happen you would rather prefer to use the pads alone, with no felt.
Edited by Ron12 - 8/20/14 at 3:38am