Superlux HD668B Stock or Modded? Post your mods here
Sep 25, 2016 at 10:13 AM Post #31 of 32
  This is my easy mod for remove heights and sibilances. It works and affects only heights. Photos for you:
https://www.zonerama.com/photos/68415027_1200x800_16.jpg
https://www.zonerama.com/photos/68415126_1200x800_16.jpg
Notes: Use quality soft tissue (it consist of 3 slices). Diameter of circle is 3 cm. 
If you want even less heights, use coffee filter. But it removes middle a little.

After reading a long discussion on modding the 662-Evo in another forum, I would stay away from coffee filters - they're not porous enough, so they don't let the air pass through with friction as much as they absorb the energy through elastic movement, acting like a second, passive membrane, which has other unwanted effects on the sound (I suspect it adds delay and muddies up the transients among other things). I'd only use the most breathable paper possible, and - as shown in your picture - I'd try to make sure the paper stays in place across most of its surface by adding some sort of "ribs" to hold it in place, so that it never moves back and forth like a passive membrane. We only want it to resist the air movement through porous friction, not through membrane-like movement.
 
Sep 25, 2016 at 12:44 PM Post #32 of 32
  After reading a long discussion on modding the 661-Evo in another forum, I would stay away from coffee filters - they're not porous enough, so they don't let the air pass through with friction as much as they absorb the energy through elastic movement, acting like a second, passive membrane, which has other unwanted effects on the sound (I suspect it adds delay and muddies up the transients among other things). I'd only use the most breathable paper possible, and - as shown in your picture - I'd try to make sure the paper stays in place across most of its surface by adding some sort of "ribs" to hold it in place, so that it never moves back and forth like a passive membrane. We only want it to resist the air movement through porous friction, not through membrane-like movement.

Yes, for sure I added one more strip of adhesive tape to the last edge of the tissue.  (And did better looking circles :xf_eek:)). It could be well stretched (and layers somehow glued together - it would address your concern about the second membrane). Could not say, I heard any delays, tissue is also well cevered by original filter. 
 

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