NAD RP18 Mylar (bass light) Version (Modified)

Discussion in 'Audio Science' started by takato14, Mar 1, 2016.

  1. takato14

    takato14 God of Ruin

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    NAD RP18: Mylar "Bass Light" Version


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    This is one of the highly sought after 1970s Fostex T50 variants, with the big 70mm isodynamic drivers. This particular pair is the mylar or "bass light" version, with a much higher diaphragm tension than the kapton diaphragm variants.

    However, this pair is particularly special, in that it has been modified (by yours truly) with a headband and earpads from the much more recent Fostex TH500RP. The earcups of these two headphones are the exact same size and the newer headband is far lighter and more comfortable -- making the idea of a transplant far too tantalizing to resist. Sorry Hans!

    Measurements:

    Raw FR (no smoothing):

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    Distortion (R/L):

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    CSD (R/L):


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    • Slight bass imbalance -- don't read too far into this as the left earpad needs to be re-adhesed to the baffle and I'm out of double sided tape
    • 5kHz null is actually a peak in disguise
    • Slightly higher distortion on left channel
    • Very linear down to 10Hz

    Subjective impressions:
    • Neutral, maybe very slightly lush
    • Wonderful treble extension
    • Fantastic clarity and speed
    • Airy and spacious
    • Bass goes very deep with slight roll off at the absolute extremes
    • Very tight and natural sounding

    The ridge at 5kHz appears to be a measurement artifact, likely caused by the high diaphragm tension. Marvey refers to this phenomenon as "ortho wall" ringing, and similar behavior is witnessed on his measurements of the LCD-3 and some other high-tension planars. While I cannot guarantee this is what is going on here, I can say I strongly believe this is the case as I do not hear anything of the sort on my subjective tests.

    My measurement process: https://dl.dropboxusercontent.com/u/34404748/noDel/BL_F/meas/PROCESS.txt

    A big thanks (and apology :oops:) to Hans for the TH500RP!

    Better photos will be added when I get the earpads attached correctly.


    ~W.
     
  2. takato14

    takato14 God of Ruin

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    Found some double sided tape!

    [​IMG]

    THD and CSD results are largely unchaged, but now the bass is mostly flat on both channels.
     
  3. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    LOL, no need to apologize for cannibalizing the TH500RP. You bought it, and it's yours to do with what you will. :) Did you grab comparative measurements before, at least? :p
     
  4. takato14

    takato14 God of Ruin

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    Uwahaha! Yeah, I did take some measurements of the TH500RP. I'll post them in a while.
     
  5. MF_Kitten

    MF_Kitten Banned per own request

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    I highly recommend fluffy cotton and stiff felt behind the driver, perhaps in a donut configuration to avoid choking the low end. Dampening smoothens out the frequency response a bunch.
     

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