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In the early days of filmmaking, movies were
made with images only, no sound. In 1927, however, a new era was
entered with the movie "Jazz Singer', in which sound was
introduced. This was the first step in theatre sound-effects
technology, one that has led to major developments in the
industry. Movie sound technology began with monaural sound and has
evolved to include stereophonic and Surround Sound.
Now, there are a number of advanced technologies that
significantly improve audio performance in movie theatres. These
advanced technologies include Dolby Digital,
DTS, and the
THX
system. These technologies can also be enjoyed at home. Let's take
a look at these technologies.
In a movie theatre viewed from above, you would find the speakers
are arranged so as to surround the audience. Speakers are placed
In front of the screen along the walls to the left and right oft
the audience and to the rear.
By contrast, at home it is not easy to arrange the same equipment
in the same position as in the theatre because of differences in
room size and layout as well as acoustical problems. The layout,
therefore, usually consists of left and right front, centre, and 2
surround speakers normally placed at the rear. Depending on the
system used you may also have a Low Frequency Effect (LFE) speaker
also known as a subwoofer.
Dolby Pro-Logic was the first major step forward in home theatre
systems it encodes a centre and rear channel in the existing analog audio tracks, a good effect could be achieved with a
pro-logic amp. Today's Dolby Digital and DTS systems use a totally
digital signal to achieve 5.1 channels.
All six speakers are controlled independently in the Dolby Digital
and the DTS sound systems. In addition, in the Dolby Pro Logic
system, the Left Surround (LS) speaker and the Right Surround (RS)
speaker receive the same signals (monaural), and the system does
not have Low Frequency Effect (LFE). The LFE is for low sound and
counted as 0.1 channel and it is this reason that Dolby Digital
and DTS are often called 5.1 systems. Therefore the pro-logic
system would be called a 4 system (seeing the rear speakers are
mono).
Most amps sold today are backward compatible, therefore if you
purchase a DTS amp you will be able to play Dolby digital and
Pro-Logic signals as well as the DTS signals.
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