How 5.1 Works
By: Paul Sonoda
In November of 1940 a movie stunned audiences with sound effects coming from different places in the movie hall. Movie goers were forever changed by the effect of sound on a movie experience. The movie was Disney’s Fantasia. Since then, we have had many improvements to multi-channel recording and playback. One of the latest advancements is 5.1. Originally design for movie playback, 5.1 has exploded on the consumer scene in high-end home theater systems. Today, 5.1 is not only available to the home theater masses, it is available in the mobile arena as well.
What is 5.1
5.1 is a multi-channel recording format designed to enhance the movie experience in the home and now mobile theater. 5.1 differs from other multi-channel configurations in its implementation. True 5.1 is the playback of 5 separate, digitally recorded channels of music, speech or sound effects plus the addition of a mono output low-frequency subwoofer channel. Only with the availability of DVD has the potential for true 5.1 been available to the consumer public.
Designed for the enhancement of movie soundtracks, 5.1 consists of three front channels (left, center and right) and two rear surround channels. The center channel handles most of the speech or talking in the movies while the other channels reproduce the special effects to add realism to the movie experience. Today, 5.1 also is available as music only recordings. The numbers of artists recording high-fidelity multi-channel recordings is currently small but growing at a rapid pace. To the mass of consumers, 5.1 has also come to mean any multi-channel. Knowing the difference between multi-channel and 5.1 will help you assist customers to make the right purchase decisions.
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topAnalog versus Discrete
Multi-channel playback systems are divided into two camps: analog and discrete. While the end results are similar, there are some significant differences. Analog multi-channel systems interpolate 5.1 audio by decoding a two channel audio signal to create a center channel, subwoofer channel and two surround channels. One of the best examples of this type of device is the Rockford Fosgate RFQ 5000 with Dolby Pro Logic II processing. On the OEM side, companies like Volvo, and Aston Martin offer Dolby’s Pro Logic and Pro Logic II surround sound as optional equipment. The advantage to analog decoders is the ability to take any existing two channel signal from a CD or even the FM radio and get a convincing surround sound in your vehicle.
A discrete system generates the 5.1 audio channels by decoding a data stream that includes individually recorded information for left, center, right front channels, left and right rear surround channels and a mono subwoofer channel. The advantage to this format is accuracy and sound quality. By using discrete channels, the listener is hears multi-channel recording as it was intended by the artist who made the movie soundtrack or audio recording. While the process sounds easy, the implementation is quite complex. Currently, there are two competing digital 5.1 formats: Dolby Digital and DTS.
Format Wars
Just like VHS and BETA, digital 5.1 has Dolby Digital and DTS. In June 1992, Batman Returns is the first movie released in Dolby Digital. Only eight months later in February 1993, Jurassic Park marked the introduction of DTS and the beginning of the 5.1 format wars. Unlike the tape wars, Dolby Digital and DTS are different forms of decoding and can exist together and do on many home decoders and car audio equipment available from Alpine, Clarion, Eclipse, Kenwood and Panasonic.
Which one is better? That depends on who you talk to. DTS claims superior sound quality due to less compressed audio signal. Dolby claims great sound quality and offers more titles available (at least in movies) and more components and vehicles available with Dolby Digital decoding. What is important to you is that both formats offer discrete multi-channel sound for movies or music. With either format you will experience a new high in your vehicle’s sound quality. Which one should you choose? I say both. There are several companies that offer DVD players and outboard processors that will decode both Dolby Digital and DTS.
What does it take? (Speakers, Amplifiers and Processors oh my!)
Ok so now you want 5.1. What will it take? The first thing you will need
to do is decide on your 5.1 decoder. There are many great choices which
one is right for you will be based on your particular need and, of course,
your budget. Included in this article is a list of aftermarket companies
that offer 5.1 products.
Speakers are the most important choice you will need to make. The most challenging aspect to the speakers is installing the center channel. In most vehicles, there are good placements for the left and right speakers, but only a few vehicles come with factory locations for the center channel. Customers will look towards the specialty retailer like you to address to solve their center channel installation challenges. For optimal results, the front three channels need to have similar frequency response and sound quality. The closer in sound they are, the more convincing your system will become. The rear speakers should also have the same sound. Pick a subwoofer to compliment the tonal quality and SPL requirements of your system.
Last but not least is amplification. Ideally, all 5 channels should have the same power level. Several companies have introduced 5-channel amplifiers designed for just this application. The expensive route would be to use a dedicated amplifier for each channel. The last resort would be to use 5 channels of a 6-channel amplifier. While this might seem wasteful (it is!), it would be better to waste one amplifier channel than to create an imbalanced of power between the channels. Choose a subwoofer amplifier to match the power SPL and power handing requirement. Careful, thorough, decisions on speakers and amplifiers will allow you to get the most out of your multi-channel 5.1 system.
Summary
In 2003, the largest growth in the mobile electronics industry was mobile video. With new releases of DVD audio, 5.1 could be the next big growth segment in the car audio industry. The people at Acura think this. The newly released Acura TL includes 5.1 Dolby Digital and DTS as standard equipment. For all the rest of us don’t buy the TL, 5.1 is a technology that can enhance the sound of every systems as well as provide new opportunities to upgrade our customers existing systems.
