Why Do I Need to Balance Output Levels for All Channels in a Surround Sound System and What’s the Best Way to Do So?
Level balancing (using your AVR’s built-in test tone generator) makes sure that your system is precisely calibrated to match the acoustical properties of your room, just as technicians do when they’re installing a high-quality sound system in a movie theater.
After you’ve calibrated your system, any difference in Inter-channel levels will be totally controlled by the audio signal from the software you’re playing, and not influenced by some room-specific or system-specific artifact.
That’s why all surround systems give you some way of adjusting relative levels for each channel individually so that they all sound equally loud at your ears. In other words, a well-designed surround sound system will let you compensate for different speaker placement and differing speaker efficiencies. After you’ve done this, you can use the master volume control to change the overall system level without affecting critical channel-to-channel relationships.
After you’ve placed all the speakers in your surround system in the best place, you’ll need to calibrate the system by adjusting each channel’s level (or "trim") control individually. Although most Owner’s Manuals state that you can do this by ear, we recommend that you use a sound level meter for real accuracy. Don’t worry, these gadgets are not expensive or difficult to use. You can even download apps for smartphones that can do this task. If you are using your AVR’s room correction software you can always go in and check those values as well to see if they are set close to the measured value.
Although unit-by-unit differences exist for SPL meters and Apps, here’s a brief overview of the calibration process:
- Set your sound level meter (SPL meter / or App) to "C" weighting. Don’t worry about other scales for now -- the "C" scale is the best match for the way we hear. Select "Slow" response -- "Fast" doesn’t give as clear a picture of the average sound level and we’re looking for average readings for best accuracy. Set the Range selector at "70."
- Place the sound level meter as close to where your ears will be when you’re in your favorite listening/viewing position. This means you should hold it at ear height but as far away from anything -- especially your body -- that might reflect sound into the meter’s microphone and upset the reading.
- Turn on the test tone signal. Set the volume to reference level: "00" or “0.0db” by the volume control.
- Begin calibration by adjusting each channel so that its relative output produces a reading of 75 dB on the meter. (You may feel more comfortable setting the meter’s Range to 80 and then reading down from there to 75. You’ll probably have to cycle through all channels several times until you’ve got the same reading on the meter for each channel. Don’t worry -- just take your time and exercise a little patience. Remember, once you’ve done this once, you won’t have to do it again.
Once completed you will have a level matched system and will enjoy a very cohesive surround sound system.