How to Get Dolby Digital
5.1 Channel Surround
Here's a surprisingly common problem�You've set up your new Dolby Digital/dts A/V receiver, Axiom 5.1-channel home theater surround system and DVD player, popped in a DVD, and pressed �Play.� The movie starts, the sound from your main stereo speakers is great, but somehow the surround effects seem to be lacking . . .
You panic! Is my new receiver defective? Is the hookup wrong? Maybe the surround levels need adjustment? Aren't these new �multipolar� surround speakers supposed to be all enveloping, immersing me in an involving and realistic soundfield? Did I position them incorrectly?
I answer email questions about this all-too-common scenario every week. The last query was from a user whose new A/V receiver wouldn't switch into the Dolby Digital mode, and refused to display �Dolby Digital� on its front panel. He also was disappointed with what few surround effects he could hear.
The truth of the matter is he wasn't hearing any surround effects at all--because his new A/V receiver wasn't operating in Dolby Digital 5.1! He was listening to the movie in stereo because he hadn't set up the DVD player's menu to output a 5.1-channel Dolby Digital bitstream, and he hadn't connected the DVD player's digital output jack to the A/V receiver's digital input.
Now, here's how to do it correctly (the following instructions assume that you own a Dolby Digital/dts 5.1 to 7.1-channel A/V receiver with digital inputs and a DVD player with a digital output jack, either coaxial or optical or both):
- Connect your DVD player with either a single digital coaxial or optical digital cable from the DVD player's digital output jack to the digital input that corresponds to the DVD input on the A/V receiver. There is no difference in sound quality between these two types of connectors. Your DVD player may have only one type. If it has both, use whichever one is convenient. (There is no need to connect the analog left and right audio cables to the A/V receiver except in special circumstances.) Note: While you are at it, do not forget to connect the video cable, because the DVD player's digital output does not carry the video signal.
- The next step is crucially important. DVDs do not necessarily default automatically to Dolby Digital 5.1. Each time you load a DVD, go to the DVD's setup menu and click on "Audio Setup" or on "Languages" if there is no Audio Setup option and choose "Dolby Digital 5.1." (If you have a 6.1 or 7.1 system select "Dolby Digital EX" if it is an available option.) Depending on the age of the disc, the "Audio Setup" on the DVD menu may give you several choices: "5.1 Channel Surround Sound" or "Stereo Playback." If it's an old DVD, it might even say Dolby AC-3 (the professional designation for Dolby Digital 5.1). New DVDs may offer "Dolby Digital 5.1" and "Dolby Digital 2.0," the latter being stereo. A sampling of my own DVDs, which date back to 1997, show all variations. Some of the disc menus offer only "Surround Sound" or "Stereo" options.
- You should now see "Dolby Digital" displayed on your TV screen or on the display on your receiver. If this does not appear, you may need to go to the DVD player's menu and set the bitstream for Dolby Digital. You will need to refer to your DVD player's owner's manual to find out how to set this for your machine. Note: Fortunately this is a one-time set-up.
- The single digital cable connector--either a plain coaxial cable with RCA male plugs on each end or a Toslink optical connector--carries the entire Dolby Digital 5.1(and dts if its available) -channel data stream to the receiver. It also carries a digital "flag" that signals your A/V receiver's Dolby Digital 5.1-channel decoder to switch to its Dolby Digital mode and send the multichannel audio signals to your system's six speakers. When it detects the digital flag, the receiver front panel should display "Dolby Digital" or indicate it with an LED or with text on the TV screen.
Another thing to remember: Dolby Digital is the world standard for 5.1-channel DVD movie surround soundtracks, digital cable-TV distribution and for satellite broadcasts of movies and programming. DTS is only an option for the producer of the DVD or music disc. The Audio Setup menu may or may not list dts, depending on whether or not the disc's producer decided to offer a dts soundtrack mix in addition to Dolby Digital 5.1. Lots of older DVD music videos do not include a dts soundtrack. Dts soundtracks are separately mastered and may have a different tonal balance from Dolby Digital. Many older first-generation DVD players do not read or pass a dts signal.
Once you have properly connected the DVD player's video and optical or coaxial digital cables to your receiver, go to your receiver's remote or front panel and turn on the �Test� signal that cycles a pink-noise signal consecutively through the left front, center, right front and the surround speakers. Make sure you hear the test signal from each speaker. Now adjust the levels carefully either by ear or with a sound-level meter from your listening location (much more accurate adjustments are possible using a separate sound-level meter such as the Radio Shack meter, available at modest cost with either an analog or digital display. It's a worthwhile accessory for accurate home theater channel-level adjustments).
Finally, check the polarity of all your speaker connections, making sure that the red and black speaker outputs on your receiver match the red and black connectors on each speaker. That will ensure that all the speakers operate in phase, with all of the drivers' diaphragms moving in and out together.
Do not rely on some new A/V receivers' auto-phase or auto-equalization circuits or on test discs that utilize microphones. Many are erratic in operation, indicating that some speakers are out of phase when in fact they are not or suggesting that adjustments are needed to alter the frequency response. The auto-EQ or interactive test discs will make good, neutral speakers like Axioms reproduce the unnatural response that has been electronically created and greatly deteriorate your home theater enjoyment. Use these circuits to adjust the channel levels only, then turn them off.
As a final reminder, don't forget to go to the DVD menu and click on Audio Setup and 5.1-channel surround sound every time you load a DVD. You've paid for all those multiple channels of sound reproduction, and you deserve to hear the movie the way it was mixed.
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