The NAD RP18 was an OEM variant of the vintage Fostex T50 from 1974. It was aimed for the German market (I’m not sure about this information). This is a planar headphone and it’s known to have 2 variations : mylar and kapton diaphragms, with different tensions. My pair is a mylar RP18.
Build is sturdy but they are not comfortable : stock on-ear pads are too hard and thicker alternative pads expand the headband to its limit and causes pain on top of my head. They are quite heavy (410g) considering their very thin ear cups and design.
○ Release : 1977
○ Current status : Discontinued
○ Type : Over-ear / Open-back
○ Measured weight : 412g
○ Impedance : 60 Ohms
○ Sensitivity : ~93dB/mW
○ Average used price : $200-300
With stock pads
Very warm and mid-centric. Bass hits very hard, I’m impressed. A bit loose and lacking control below 40hz. Midrange is pretty forward with an emphasis around 3-4khz, a bit stronger than the HD600. It can definitely be shouty on some tracks. The treble is too rolled-off compared to the bass and midrange.
As a result, they sound warm, sometimes dark if the music does not emphasize the upper-mids. A bit veiled sounding. Technicalities are excellent considering the age of the NAD, but not as good as some of the best current mid-fi gear. Resolution is a bit below an HD600, but dynamics are more contrasted.
With alternative pads
I tried many pads. My initial goal was to improve the comfort, and to give more energy to the treble while lowering the upper-mids and keeping the bass / body. Unfortunately, I don’t think any pads gave me the exact results I wanted. Some additional modding / dampening changes may be required, or simply, EQ.
Best pads were fake ZMF Ori pads. Improvement in soundstage width and tonal balance, but the presentation becomes much drier. The treble is a little bit strong around 9-10 khz, and there is another extra-boost given to the upper-treble. Bass still hits hard (very similar to an Audeze LCD). They do sound a little V-shaped, with a dry midrange, quite the opposite compared to the mellow and forward midrange with stock pads.
This NAD RP18 is one of the best vintage (pre-2000) headphones I’ve heard, with good modding / pad-rolling potential and decent punch. It is difficult to find and a bit sought after ; I’d still prefer an Hifiman Sundara, HE500 (used, around $300-400) or a Verum, both of them being more comfortable and with better sound than a stock RP18. It’s mostly a collector item, not easy to find, with poor ergonomics compared to modern headphones.
Measurements & Resources
Changstar measurements and impressions