RapVerse.com Community - View Single Post - Decibels, Frequencies, Format Comparisons

FORMAT COMPARISONS
ALL ARE APPROXIMATE

human ear capacity: Dynamic range = 100 dB. Frequency response = 20 Hz to 20 kHz.

DVD: Dynamic range = 106 dB (* see note). Frequency response = 0 Hz to 20 kHz.

CD / DAT: Dynamic range = 96 dB (* see note). Frequency response = 0 Hz to 20 kHz.

MiniDisc: Dynamic range = 96 dB (* see note). Frequency response = 0 Hz to 20 kHz.

12-inch vinyl: Dynamic range = 20 dB (* see note). Frequency response = 50 Hz to 22 kHz.

7-inch 45: Dynamic range = 20 dB (* see note). Frequency response = 50 Hz to 12 kHz. (Usually were either vinyl, shellac, or polystyrene.)

TV / hi-fi VHS / FM radio: Dynamic range = 60 dB (* * see note). Frequency response = 20 Hz to 15 kHz. (NOTE: Ordinary "non-hi-fi" VHS sounds only about as good as a normal cassette.)

metal cassette (Type IV): Dynamic range = 65 dB (with Dolby B = 70 dB; with Dolby C = 80 dB.) Frequency response = 20 Hz to 18 kHz. (The tape is layered with fine metal particles. Sounds excellent, but is somewhat abrasive on tape heads. Also tends to snap easily.)

ferro-chrome cassette (Type III): (This mixture of metal and chrome oxide particles was an experimental format that never caught on. Went the way of the eight-track cartridge. By the way, there is a Type 0 too, that is likewise disappearing. It is similar to normal tape in formula, but apparently has some problems.)

chrome cassette (Type II): Dynamic range = 60 dB (with Dolby B = 65 dB; with Dolby C = 75 dB * see note). Frequency response = 20 Hz to 16 kHz. (Formulated of a substance derived from chrome, which is then mixed with iron rust particles. A fine compromise between great sound and tape head-friendliness.)

normal cassette (Type I): Dynamic range = 55 dB (with Dolby B = 60 dB; with Dolby C = 70 dB * see note). Frequency response = 20 Hz to 14 kHz. (Made with ferric oxide - the rust that comes from iron. Sound quality is acceptable; material is very easy on tape heads.)

MP3: Dynamic range = 20 dB (most people don't utilize this full range -- they heavily compress). Frequency response = 20 Hz to 12 kHz.

AM radio: Dynamic range = 30 dB (* * see note). Frequency response = 20 Hz to10 kHz.

typical home stereo speaker: Dynamic range = 90 dB. Frequency response = 80 Hz to 20 kHz.

typical cheap computer speaker: Dynamic range = 70 dB. Frequency response = 200 Hz to 15 kHz.

NOTES:

* Most popular music releases are compressed to about 20 - 30 dB, regardless of the dynamic range the format is capable of handling. In the days of vinyl, this was done for the purpose of getting the sound acceptably recorded onto the records. Too much dynamic energy was detrimental to these discs; it messed up both the recording and the playback, because it made the needles jump out of the grooves. Due to this, the stereos that were made to play these records were designed to handle no more than this narrow dynamic range...anything more would have been unnecessary. (It never occurred to them that one day we would develop a format which could handle a wider range -- namely, the CD). Today, we have several formats which are capable of HUGE dynamics, yet we still use with stereo systems that have narrow dynamic range capability. Why? Because we have become so accustomed to hearing highly-squashed music, most of us are turned off by recordings with natural-sounding dynamics. Que loco.

* * Major commercial TV / radio stations routinely compress their broadcasts to less than 10 dB. This is done for two reasons: (1) to make their station sound as loud as the competition; and (2) to keep their volume level steady so you don't have to constantly adjust your stereo. (Don't kid yourself...it's mainly the first reason.) They use multi-band compression to keep the sound from getting too smeared. A multi-band compressor is one that isolates the bass, midrange and treble portions of a sound and allows you to compress each band seperately, so nothing gets more treatment than it needs. Generally, bass is compressed fairly heavily; midrange to a lesser degree; and treble very slightly if at all. This is all followed by an overall limiter, which prevents anything from getting through above the safety margin.