Now you've got the
equipment and think you're set, right? Read On.
You have finally decided to purchase the Dolby Surround Pro Logic equipment together with a very good HiFi stereo video recorder. You unpack everything and in no time you wired everything up and stacked everything neatly in its place. While you were at it you even bought a good movie and made sure that the packaging said that it is a Dolby Surround sound film. You fire it all up and sit back to enjoy this wonderful new cinema sound experience. You're amazed at the way the room is transformed. However it is highly likely that you may not be getting the best sound out of the set up just yet.
What have I done
wrong?
Not much but getting the utmost from the equipment is all done by careful placement of the speakers, sitting in the right viewing/listening position and balancing carefully the sound across the front soundstage as well as the rear surround effect channel. Do not think that this is a simple task as it is not, and a good setup requires hours of testing and shuffling between knobs and levels. The same thing happened to me when I first set up my equipment and at times I still sit to watch a movie and after a while I say to myself that something is not right with the sound distribution. This is true but the cause may not necessarily be in your setup. A movie's soundtrack may well be recorded in Dolby Surround but we are not always getting our money's worth in the "thrills per £" ratio. This is a fact and we can do nothing about it. We only get to listen to what effects the director and sound engineer decided to mix in the final soundtrack. I only realised how true this was when I bought a "Surround Test CD" produced by Finlandia Records. But more about fine tuning later. First, let us handle the more basic issues that help improve the sound of any Dolby Surround setup.
Speaker Placement
The key to obtaining a perfect stereo and surround image is to have all the speakers placed correctly relative to the listening/viewing position. They also have to be perfectly balanced so that sound coming from the front three is not louder than the rears. Remember that unless you own rather expensive equipment, it is likely that the rears are already underpowered compared to the front channels. So how do you go about placing the speakers.
The front stereo speakers should ideally be positioned as far between as they are likely to be away from you. The TV should be positioned in a central position. The Centre speaker as the name suggests must be placed directly above or below the picture. The surround channel speakers as I said earlier, have lower power and are also likely to be much smaller so these have to be located closer to the listening position. Surround speakers are best placed hanging to the rear wall or placed on good rigid speaker stands slightly further back and to each side of your viewing/listening position. Experimentation is the best way to find the correct position but I found that the best solution is to have them placed 12" to 25" further back depending on the amount of power they are receiving.
All speakers should be placed at ear level height. Some sources claim that surround speakers should be placed 6' to 7' high and others even claim that they are best placed higher. I have experimented with this and found that placing them at ear level worked best.
These recommendations are as good as the room permits. Other factors have to be taken into consideration. Furniture, carpeting, curtains etc. play an important part in the placement of your equipment, but do not expect a good soundstage if space restrictions force you to deviate from the above placement recommendations and listening/viewing positions.
How do I know if I
have got everything balanced right?
Every Dolby Surround Pro Logic amp comes with a crude built-in test-tone for helping you to balance the four channels for optimum sound. At best, when you are done using this aid, a pink noise generator, for channel balance adjustment, your balance is, at best, only approximate. When this tone is activated, the noise signal starts to circulate between the channels at 1 to 2 second intervals. Channel balance is adjusted by means of Centre and Surround level controls so that the sound coming from these channels is approximately the same level as that coming out of the front pair. The spectral content of the test noise generated by surround decoders, varies considerably. Also different speakers have different tonalities, especially in the rear channel. Due to these factors it may be difficult to set the channel balance with a decoder's test tone. It is best to invest in good surround sound test cd like the one I mentioned above. Apart from a more accurate test tones, it has no less than 79 test tracks ranging from constant frequency panning signals to choral music, orchestra, church music, spoken channel identification, sound effects etc. What I can say is that I am frequently inserting it back into the CD player and rerun some of the tests whenever I change a component or the placing of the speakers.
In part three of this article we will be talking about higher levels of Home Cinema Equipment and Sound including Dolby Digital, DTS and DVD Video.
© 1998-2003 Mario Sammut
Reproduction in whole or in part without express written permission is prohibited.