XDR (audio)

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The XDR logo, on the label and case insert of cassettes duplicated with the XDR process XDR logo.png
The XDR logo, on the label and case insert of cassettes duplicated with the XDR process

XDR (expanded dynamic range), also known as SDR (super dynamic range) is a quality-control and duplication process for the mass-production of pre-recorded audio cassettes. It is a process designed to provide higher quality audio on pre-recorded cassettes by checking the sound quality at all stages of the tape duplication process. In this way, the dynamic range of audio recorded on an XDR-duplicated cassette can be up to 13 decibels greater. [1]

Contents

History

XDR (Expanded Dynamic Range) was originally developed by Capitol Records in LA in their R&D facility.

Before they had released anything, Capitol Records-EMI of Canada was made aware of this activity and was able to release their own version called SDR (Super Dynamic Range) ahead of the American version. They managed this because:

After some time Capitol Records Canada was asked to re-brand to "XDR". [2] to put Capitol Records Canada in line with the rest of Capitol Records.

Process

The XDR/SDR process involves many steps, the most prominent being:

As well as with EMI & Capitol Records, PolyGram and other labels also offered cassette releases duplicated with the XDR process.

Test Tones

Spectrogram of SDR Soundburst from cassette of David Bowie's "Let's Dance" SDR Spectrogram - Let's Dance.png
Spectrogram of SDR Soundburst from cassette of David Bowie's "Let's Dance"

Several different tonebursts were used during the life of the XDR/SDR process.

Album ID

Listen to an example of XDR's dual tones
Example XDR data: Chameleon Records #74819
470Hz604Hz*
470Hz816HzD
470Hz816HzD
426Hz604Hz7
426Hz604Hz7
385Hz604Hz4
426Hz668Hz8
348Hz604Hz1
426Hz738Hz9
385Hz816HzB

XDR tonebursts tend to be at both the beginning of side 1 and end of side 2. Some XDR cassettes include a series of DTMF-like dual-tones after the second toneburst at the end of the tape which uniquely identifies the album. Each dual-tone is 65 milliseconds long and separated by 35 milliseconds of silence. XDR's dual-tones are a modified form of DTMF where each of the two frequencies is one-half the usual specification.

XDR's modified DTMF frequencies (with sound)
604.5 Hz668.0 Hz738.5 Hz816.5 Hz
348.5 Hz 1 2 3 A
385.0 Hz 4 5 6 B
426.0 Hz 7 8 9 C
470.5 Hz * 0 # D
Note the dual tone data following the XDR soundburst. Spectrogram-dramarama2.png
Note the dual tone data following the XDR soundburst.

References