A few days ago, I had the opportunity to hear some music from a top-of-the-line SACD system. I had never heard a SACD disk before, and I was amazed by the clarity and richness of the sound. This posting is a tribute to the people at Sony and Phillips who brought us this outstanding technology, and a thanks to the friend who opened my eyes (ears?) to this format.
Super Audio CD quality is built on 3 factors:
The first and most important is the sampling rate. Super Audio CD uses Sony’s Direct Stream Digital process, which samples music at 2.8224 MHz. This is 64 times the sampling frequency of a standard Compact Disc.
The second is the frequency response. The SACD offers a frequency response of 100 KHz, which is almost 5 times that of a CD. CDs do not respond to frequencies above 22.05KHz. Although humans are supposed to be deaf above approximately 20KHz, there is evidence that we can sense high-frequency sounds. See this interesting paper for a discussion of ultrasonic musical instruments (eg cymbals) and how people perceive them.
The third is dynamic range, which is the ratio of the softest sound to the loudest. SACD provides a dynamic range of 120dB, compared to the 96dB provided by CDs.
The above specs mean that a SACD contains about 7 times as much music detail as a standard CD. When combined with SACD’s support for 5.1 channels of surround sound, this format is impressive.
Other features of the SACD format include hardware-based copy protection and downconversion to 16-bit/44.1 kHz digital audio for use on conventional CD players. SACD uses 2 types of watermarks: an “invisible” watermark, which can only be detected by the Super Audio CD player, and a “visible” watermark, which is imprinted on CDs. If a counterfeit disc is inserted in the Super Audio CD player, the player detects the absence of the invisible watermark and prevents playback.
A competing high resolution audio format is DVD Audio. The numbers for DVD-A are: Sampling rate = 96 KHz; Frequency response = 48 KHz; Dynamic range = 144dB. Of the 2 high-res formats, the Super Audio CD captures more data, and so it should offer a more faithful rendition of the original music.
See here for a discussion on the merits of various formats, including 30 ips master tapes. Also, eCoustics has a number of good articles on digital music formats.
High Fidelity Review has an article comparing the 2003 sales of the various formats:
Compact Disc Unit Shipments — 745.9 Million copies sold
Vinyl LP Unit Shipments — 1.5 Million
Super Audio CD — 1.3 Million
DVD Audio — 0.4 Million
Click here for course material on the Physics & Psychophysics of Music. See this link for a good discussion of Music and The Human Ear.
The frequency response curve (courtesy of stereophile.com) for the Sony SCD-XA9000ES pictured above, shows 50kHz at -3dB, whereas regular CDs start to fall off before 20kHz .
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