Thanks,
Arnaud! So it's between Silver Dragon, APS V3 and FA now.
I haven't posted in this thread for a while because of the lack of time and because I can't present a definitive shape of the mod – also in view of the new Melamine prespective. Meanwhile I have tried Arnaud's Melamine foam for covering the bare frame parts according to his template – with a not so favorable result: a slight upper-bass bloat and no low-bass gain to speak of. (BTW, it was with a thickness of 0.5 mm from the start.)
Initially more bass wasn't in my agenda, but has turned out to be beneficial in the form of a rounder, more relaxed and less analytical sound without any sacrifice of detail resolution. So I tend to think that covering part of the steel mesh is essential for reaching my sonic ideal with the HD 800. Still there are more variants to explore, also with the Melamine foam, but till then, here's the latest state of my mod, with which I'm quite happy:
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A) is the basic self-adhesive velours, now reduced to about 3½ cm²;
B) is an additional piece of black velvet of ~1 cm² attached to the steel mesh (by means of double-sided adhesive foil);
C) is a layer of black velvet loosely covering the velours and the bare frame parts (thus reducing reflections).
The velvet part
B) is dispensable – I haven't decided yet if I like the sound better with the bass increase it brings or without it. What I have found out, though, is that a significantly larger area of velvet/velours is too much (bass) for my taste. But if you want, you can get more bass than from the HD 650 that way. Furthermore it has turned out that a combination of velours and velvet attached to each other makes the bass boomy, similar to my first Melamine try. By contrast a loose layer of velvet on top of a velours layer doesn't do harm.
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