Considering Audio CD Compression

By eweek  |  Posted 2003-03-05 Print this article Print

and Dynamic Range"> "I dont think its really accurate to say that CDs are compressed, although the MP3 files on them certainly are. Any medium is restricted somewhat by its format. CD audio is restricted by its 16-bit, 44-Khz design. Similarly, vinyl is restricted by the properties of the vinyl as well as those of the needle and cartridge. Both of these face restrictions one or more places in the signal chain until it comes out the speakers, where they face the acoustical properties of the environment and the widely varying human ear.
More to the point, high resolution systems like Dolby Digital and DTS are also compressed (as is, I think, DVD Audio and SACD). If Im not mistaken the Dolby Digital and DTS sound at your local theatre comes off of a special purpose CD player, or at they least used to.
As a point of interest, I once read that the size of the CD was determined by what would fit in the dashboard radio in a car. It always irritated me that this restriction resulted in two CDs instead of one when the many great double record rock records of my youth—some of which were 20 or more minutes per side—were released on CD." Vince Stone "Um, Audio CDs are NOT, by definition, compressed (unless youre listening to an MP3 CD, which is a horse of a different flavor). CDs offer well over 90 db of dynamic range compared to vinyls 45 db or so. Granted, this dynamic range may not be fully utilized by the producer, but thats a human decision, not a limitation of the technology. A CDs frequency response is theoretically limited to just over 20KHz, only a dream for vinyl. Early CDs suffered from poor Analog-to-Digital conversions which could make them sound gritty or overly bright. But such is not usually the case today. Most of the bad sounds found on todays CDs are the result of poor engineering or lousy performances. What many people miss on CDs, indeed, in digital recordings of any type, is the DISTORTION inherent in most analog recording systems. When presented with excessive signal levels analog devices typically saturate gracefully while digital devices run out of bits (a bad thing). Moderate levels of this saturation produce the "fat" analog sound so many find pleasing. This is why so many high-end recordings are now made with analog devices in the signal chain: to warm up that sterile (real) sound with analog distortion. We corrupt the signal to make it sound better! While Im no great defender of the CD we still should be honest in our characterizations of it." Richard Thompson, President
T4 Media


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