XDR (audio)
Quality-control process for higher dynamic range on pre-recorded cassettes.
XDR, short for expanded dynamic range and also called SDR (super dynamic range), is a method for overseeing quality and duplication when mass-producing pre-recorded audio cassettes. It boosts audio fidelity by monitoring sound quality throughout every step of the tape duplication process. As a result, cassettes made with this process can achieve a dynamic range up to 13 decibels higher.
Quick Facts
- Dynamic range increase
- up to 13 decibels
- Developed by
- Capitol Records (LA) and Capitol Records-EMI of Canada
- Canadian release name
- SDR (Super Dynamic Range)
- Master tape width
- 1 inch
- Standard duplication master width
- 1/2 inch
Facts from the source article.
History
Before the American version was released, Capitol Records-EMI of Canada, functioning separately from the US counterpart in the early 1980s, released their own version called SDR (Super Dynamic Range) ahead of it. Capitol Records LA faced added complexity by developing the system in kit form for shipment to manufacturing facilities, and created a sophisticated high-speed tone generator to inject tones into slave duplicators. In contrast, Capitol Records Canada designed a real-time test tone generator and recorded these tones onto the one-inch master along with the music, reducing design time and allowing testing of the entire chain from master tape to final cassette. Eventually, Capitol Records Canada was asked to rebrand to XDR to align with the rest of Capitol Records.
Process
The XDR/SDR method copies cassettes from a one-inch master loop tape in a loop bin duplicator, unlike standard duplication which uses a half-inch master loop. This produces better high-frequency clarity, stronger bass, and lower noise. Some cassettes used digital tapes to create the wide-track duplication masters. A short test toneburst is recorded at the start and end of the program material to check for any loss of audio frequencies. Along with EMI and Capitol Records, PolyGram and other labels released cassettes duplicated using this XDR process.
Test Tones
Several different tonebursts were used during the life of the XDR/SDR process. One set, used by EMI Canada in 1982 as SDR, consisted of 15 sinewave tones of estimated frequencies from 50 Hz to 18300 Hz, with specific durations and silences. Another set comprised 11 sinewave tones from 32 Hz to 18000 Hz. Chords of F# sinewave tones ranging from roughly 46.25 Hz to 17739 Hz were also employed.
Album ID
XDR tonebursts are typically placed at the start of side one and the end of side two. On certain XDR cassettes, a sequence of DTMF-like dual-tones follows the second toneburst at the tape's conclusion, serving as a unique identifier for the album. Each dual-tone lasts 65 milliseconds, with a 35-millisecond silent gap between them. These tones are a modified version of DTMF, where both frequencies are halved from their usual values.
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