แผ่น quadphonic นี่ต้องมีลำโฟง surround 4 ตัวถึงจะฟังได้ ใช่หรือเปล่าครับ? ยังงงๆว่าสมัยก่อนมีระบบ surround ฟังด้วยหรือไม่
Matrix formats
With matrix formats, the four channels are converted (encoded) down to two channels. These are then passed through a two-channel transmission medium (usually an LP record) before being decoded back to four channels and presented to four speakers. This 4:2:4 process could not be accomplished without information loss. That is to say, the four channels produced at the final stage were not identical to those with which the process had begun.
[edit] SQ / Stereo Quadraphonic
SQ logo
Stereo Quadraphonic was a matrix quadraphonic system for vinyl. It was introduced by CBS in 1972, and record companies who adopted this format include: Angel, Capitol, CBS, CTI, Columbia, EMI, Epic, Eurodisc, Harvest, HMV, Seraphim, Supraphon and Vanguard.
The system was based on the work of Peter Scheiber, who created the basic mathematical formulae used to matrix four channels into two in 1970. SQ stands for "Stereo Quadraphonic." This system made good sense, as, in the absence of a quad decoder, SQ-encoded records would play as normal stereo records, and CBS stated their desire to maintain excellent compatibility between their SQ-encoded records and standard stereo systems.
The early SQ decoders could not produce more than 3dB of separation from front to back. Early "Logic" circuits were introduced to enhance separation to 20dB, but provided poor performance, very noticeable gain-pumping and an unstable 'swaying' soundfield. The SQ system also faced resistance from broadcasters since, while essentially a two-channel system and totally stereo-compatible, it could have substantial mono compatibility problems, which posed serious problems with all televisions and monophonic radios of the era. By the time that the most advanced logic system was introduced for SQ, the Tate Directional Enhancement System[2] (implemented in Jim Fosgate’s TATE 101 decoder), "quad" was already considered a failure.
A Prologic II decoder will recover some of the surround sound information present in an SQ mix, as the matrices used are somewhat similar, but directional cues will not be properly located. Some of the SQ mixes are still present on CDs, especially on early, non-remastered editions, on which the original master is, in itself, SQ. (SQ is compatible with two-channel stereo, so there was no need to create a stereo version.)
ไปค้นมาแล้ว ผมไม่ค่อยเคลียร์มากนัก แต่นั่นคือจุดเริ่มที่เป็นที่มาของ Surround ในเวลาต่อมาครับ ผมยังไม่ได้ลองฟังเลย ไว้ได้ฟังแล้ว จะมาเล่าอีกที อ้อ โครงการทดลองฟังฟอร์แมทต่างๆเดือนมิถุนา ไปถึงไหนแล้วเอ่ย
