^ Maybe my modification of a Mylar NAD RP-18 will help with your Kapton version.
NAD RP-18 Mylar Version: Repairs and Modification
June-August 2013
- Replaced cables below Y-splitter, re-soldered connections, and added new heat shrink.
- STAX Micron Glass Wool over back of drivers = 45mm disks.
- Treble Reflecting Ring with 35 mm opening over STAX Micron Glass Wool (from eBay Germany).
- 55 mm soft felt disk over inside of grill and new speaker grill cloth.
- 5 mm wide closed cell foam “Focusing Ring” around ear side of driver.
- ¼ wedge of 7 mm open cell foam over ear side of driver at 6 o’clock position.
- HiFi Man Velour Pads secured with a ring of double-sided tape.
The sound quality is very good; certainly better than when they arrived and, in my opinion, better than the all stock RP-18 Kapton version I had on hand for direct comparison. The bass digs deep but remains fast and musical without bloating. The midrange is clear, lush, and smooth. The treble details are more clear and present, without fatigue.
Back Story:
A friend sent me an unmodified set of Kapton NAD RP-18 for comparison with his previously modified set of Mylar NAD RP-18. His Mylar version required repairs and re-modification. The Kapton version initially "Wowed" me. The previously modified Mylar version sounded congested with loose boomy bass, muffled mids, and squashed treble.
I began work on the Mylar set. The cable junction at the Y-splitter was not soldered. Instead, the connections were held together by plastic tubes, heat shrink, and duct tape. I started there...below the splitter. I soldered new connections and sealed them with 3:1 heat shrink. The cup threads (only 3 per cup) had been stripped so the seal was defeated on both sides. I used my super glue re-tapping method I've successfully used many times before to re-tap new cup threads in Fostex T20/40/50RP.
Next up, "grunt work" trying many, many different materials in various configurations over the course of 6 weeks...I lost count...really. I am happy with the final results. To my "ears and gears," the repaired and re-modified Mylar NADs now sound very good and better than the stock Kapton version.
NAD RP-18 Mylar Version:
After market pads held on with strips of double sided tape. Drivers and magnets.
Here are my repairs and re-modification:
The stock dust covers were fouled with glue
debris so I Double sided tape rings for securing pads surround
replaced them with speaker grille cloth. Closed Cell Foam "focus rings"
Yellow = STAX Micron Glass Wool with gauze underlay – Left = Rear Side. Right = Ear Side
1 layer,
Double sided tape protective covering removed and ready HiFi Man Velour pads soak up excess bass produced by 2X
for pads. the ear side driver opening compared to the stock NAD pads.
Leather and pleather pads were way too bassy resulting in
Boomy Bass Bloat (B3
NAD RP-18 Kapton version. I did not remove the yellow biscuits because the owner wanted them kept in stock form: