Frequency response of CD players is commonly flat to 20kHz, before dropping like a stone.



All frequencies within a music signal must be amplified equally, from lowest bass to the highest of treble, or tonal balance will be incorrect. A CD player has no basic difficulty reproducing all audio frequencies evenly, from 20Hz to 20kHz. In practice the lower limit is a very low 2Hz and the upper limit a tightly defined and rigid 21kHz (half the 44.1kHz sampling frequency of CD). CD players have a uniform tonal balance as a result, albeit some small variation being introduced provided by differing filter arrangements. These slightly emphasise or soften treble balance and our measurements tell us this.


There are exceptions. Audionote players have slower filter cut off rates than a conventional CD players, lacking the usual form of anti-alias filter, and Pioneer, Wadia and others use slow filters that roll down output above 16kHz. Again, our frequency response measurements make this plain. Such players do sound audibly softer in their treble, with less sheen.



Some players roll down frequency response above 10kHz, with unusual filtering arrangements.


Frequency response from DVD and Blu-ray discs, played on Blu-ray players, extends to 98kHz (half the maximum sampling rate of 192kHz), or 48kHz from 96kHz sample rate recordings.



Frequency response extends to 96kHz with 192kHz sample rate audio on Blu-ray.


With SACD frequency response extends to 100kHz maximum, but often is rolled down gently above 30kHz or so. Our measurements show whether these performances have been achieved, or whether cost cutting, for example in Blu-ray analogue outputs, has degraded the expected result.



Frequency response of SACD can reach 100kHz, but is often limited to reduce supersonic noise, here to 70kHz.







Rohde & Schwarz UPV



We measure frequency response of CD and SACD players using industry standard test discs from Sony and Philips, optimised for advanced performance testing. Both spot tones and sweeps are employed. Additionally, for CD frequency response we publish a convolution of a raised cosine pulse that also gives an accurate high resolution picture. Analyser is a Rohde & Schwarz UPV.




Philips CD  test disc, carefully manufactured for accurate measurements.



Our high frequency sweeps to 48kHz and 98kHz come from a set of Rohde & Schwarz test DVDs produced by Burosch of Germany.



A wide range of high definition audio tests are provided by Burosch test discs.



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