Let's start at the very beginning. Home cinema, also known as surround sound, Dolby® (innit), Pro-logic® and home theatre, are all the same thing. All of these systems try to give the audio illusion of your being in the middle of the action, or whatever, of a film, by making sounds come from different places.
To do this you need:
Any film with a stereo soundtrack may have surround information encoded within it. This is done in such a way as not to degrade the performance of the soundtrack when played on a mono or ordinary stereo system. Many TV shows as well as films are now produced with Dolby Surround® soundtracks. Several new systems are now appearing, based on newer technologies. See digital theatre sound for more information.
Stereo TV broadcasts (NICAM), pre-recorded videotapes, CDs, DVD and laserdisc are all sources capable of providing the stereo soundtrack needed for cinema sound. BUT it is no good having a NICAM tv and using a mono VCR to play back your new copy of "Mars Attacks!", because you will not get any sort of surround sound that way. You must use a stereo source for whatever you are trying to reproduce. Some VCRs were produced using linear stereo sound. Avoid these at all costs, because 1) They sound dreadful and 2) they will not give you stereo sound on a lot of prerecorded tapes. Some music CDs are recorded in Dolby Stereo®, and these are suitable for playing back through a cinema system.Some radio (FM) broadcasts are also produced.
This is the Dolby® bit, at least for most people at the moment. The signal comes in to the processor, and is then decoded into its constituent parts. In Dolby Stereo®, this means giving a left, center, right and effects output. This is obtained by an active filtering process, as opposed to the old Dolby Surround®, which just gave stereo plus rear effects (no center channel). The center channel is effectively the mono signal that should come equally from left and right speakers in a stereo system. This signal is then removed from the left and right channels to improve focus. The center channel carries speech AND any sounds that are coming directly from the screen. The effects (or rear) speakers only carry ambient information, and have a very limited bandwidth, from 100Hz to 8kHz. This is why you do not need large effects speakers in a Pro-Logic setup. After processing, the signal then passes on to the power amplification. Units like the Yamaha DSP E-392 are NOT processors, because they also have amplifiers to drive additional loudspeakers.
Now for the easier part. When playing material in stereo, one only has two channels of amplification to worry about, and as they are doing approximately the same job, they need to be the same. With home cinema, we have three different requirements. Effects loudspeakers really do not need lots of power, although to ensure good compatibility, make sure that the amp is able to drive at least 4 ohm loudspeakers, to prevent restrictions when upgrading. For most systems and environments, 25 watts per channel for the effects speakers is ample. There is no simple way to assess amplification needs for the center and left and right speakers. If the system is going to be used to play music as well, then quality of the left and right channels is critical. Power does not equate with quality. There are plenty of amps around which deliver 30 or 40 watts per channel, which are much better than most amps claiming to deliver 100 watts or more. LISTEN BEFORE BUYING. Any decent dealer worth his/her salt will do this for you. Don't be blinded by reviews. Most income for magazines comes from advertising, not from sales from newsagents. So don't believe everything that you read. Unless you are gullible and/or stupid. In which case I suggest that you move to Chernobyl.
This is where it all comes out, although if you've made enough mistakes by now, no amount of money spent on loudspeakers will save you. As in the previous section, left and right speakers are of paramount importance if you are going to be playing a fair amount of music through the system. For Dolby® use, the center channel carries anything up to 80% of the sound information. The other speaker that can change your whole outlook on home cinema is a good sub-woofer. If you are thinking about adding a sub-woofer to your system, make sure that it is an active unit (i.e. it has a dedicated amplifier already built in). If not, it probably won't sound very good, And you will probably end up ditching it soon. A system with a good center and a good sub with reasonable left, right and effects speakers can sound stunning. I know. Any system with a poor center speaker will sound poor. Also, imho, subs tend not to sound very good with music.
The bigger the better, but don't sacrifice all pretence of quality to get a twenty by twenty pixel screen that's ten feet wide. Be sensible, taking into account your budget, room size, distance to screen, type of material being viewed and long term plans. Personally, I think that it is still too early to invest in a widescreen set, especially as you can buy a decent 33" 4:3 set for about the same money as a decent 32" 16:9 set, and the 4:3 set is only just over 1cm, yes that's one centimeter, less wide than the 16:9 set, but has about 30% more viewing area. Maybe things will be different when we get DVD, digital satellite and digital terrestrial broadcasts up and running.
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