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There are many considerations involved in designing your home theater for quality sound.

Of primary importance is speaker placement. It is advisable to pin down your furniture layout with speaker locations in mind. Speakers and subwoofers can be hidden behind the wall covering or concealed behind the decorative grilles of an A/V cabinet. Subwoofers may even be placed underneath the flooring if they are worked into your house plans.

Also realize that noise can be a problem—not only the distraction of traffic and other external sounds, but also the broadcasting of unwanted noise to others in your home—so you may wish to have your home theater soundproofed. Soundproofing involves techniques applied by the builder and the home systems installation firm. Studs may be positioned differently and a special type of insulation may be used.

And if you are soundproofing your home theater, you will want to choose your wall treatment from among the many colors, fabrics, and shapes that are available in acoustical tile.

	Different Types of Sound Systems Explained The sound systems available for home theater include: Dolby Pro Logic Dolby Digital DTS THX Surround EX The format you choose depends on the level of performance you are willing to accept, and the amount of money you wish to spend. You may wish to take into consideration equipment that you already have. Dolby Pro Logic Dolby Pro Logic is the simplest and least expensive sound format. It has 4 channels that are compressed into two analog channels, so that you can record it on your stereo VCR. It also can be broadcast over analog radio or cable TV. Another advantage of Dolby Pro Logic is that it can be easily downconverted from a Dolby Digital signal. The four channels are as follows: 2 discrete, full-bandwidth channels (left front, right front), 1 matrixed full-bandwidth center channel, and 1 matrixed, limited-width channel that goes to 2 surround speakers. The Dolby Pro Logic encoder takes 4 channels (L (left), R (right), C (center), S (surround) and creates two output channels (Left, Right). L goes to Left and R goes to Right without modifications. C, after a 3dB level reduction, gets divided equally between Left and Right. The bandwidth of S gets limited to a 100Hz to 7 kHz range, and is encoded with a form of Dolby B noise reduction. After that it is divided between Left and Right, but with +90 and -90 degree phase shifts. During the playback, the surround is extracted by analyzing the difference between Left and Right. The major disadvantage of Dolby Pro Logic is that both surround speakers produce the same sound from the same channel (i.e. mono sound) and are limited in bandwidth. Additionally, there is no discrete subwoofer channel specified in the standard, so the subwoofer channel has to be extracted from other channels. Media sources for Dolby Pro Logic include TV shows and movies, videotapes, other analog sources, and downconverted signal from Dolby Digital (DVD, for example). Dolby Digital Dolby Digital is a 6-channel format, referred to as "5.1-channel." All 6 channels are discrete, and 5 are full-bandwidth; the ".1" refers to a subwoofer channel, which supplies Low Frequency Effects (LFE). Audio coding, known as "perceptual coding," is used to compress data with minimal loss of sound quality. Dolby Digital uses a third generation audio coding algorithm (AC-3). The channels are: front left, front right, center, surround left, surround right and subwoofer. Advantages over Dolby Pro Logic include the fact that all channels are digital an discrete, and 5 of them are full-bandwidth. Additionally, the surround speakers use separate left and right channels (stereo). Media sources include all DVDs, some DBS broadcasts, and some HDTV programs. DTS DTS is also a 6-channel format ("5.1-channel"). The main difference from Dolby Digital is that DTS uses less compression, thus providing marginally better sound. DTS is less widespread than Dolby Digital. Media sources include some DVDs and CDs. THX Surround EX THX Surround EX takes the Dolby Digital signal and creates another additional matrixed channel, which is then sent to one or two surround speakers, thus giving 6.1 or 7.1 sound. Media sources include specially encoded THX Surround EX DVDs, or regular Dolby Digital sources plus the use of a THX Surround EX decoder.

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