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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The Physics & Psychophysics of Music was fascinating. A very rich and complex topic, one which many music lovers have little knowledge of.