How To Set Channel Levels, Speaker Crossovers And Speaker Phase

Radio Shack for years has sold one of the less expensive sound pressure level meters on the market. It is commonly used to set channel levels. I see a wide variety of methods advocated on how to use this device and others to set channel levels for home theater. The method I describe here advocates using a combination of the Goldline Toolkit 5.1 DVD and Avia DVD to get your system levels correct along with finding phase errors that are required to get the proper subwoofer and speaker integration. I find the following approach results in a surround experience that closely matches that found in professional mix theaters if executed properly and the speakers are in proper locations. This procedure can be used to check Audyssey, but it may be necessary to turn Audyssey equalization off to correct for problems created by Audyssey. I find most systems perform better with the built-in automatic equalization off instead of on. This procedure does not cover how to best setup multiple subwoofers which is much more complex than the process described here and very dependent on the room and equipment available.

The Avia DVD contains tests that are useful for setting channel levels, speaker phase, subwoofer phase and subwoofer level for bass management purposes. The Goldline DVD contains tests that are not found on Avia for setting channel levels by ear, back channel levels and ensuring the LFE level is correct. The Avia channel level tests are too slow to be good for verifying levels by ear. Avia also lacks a true LFE signal. All of the subwoofer test signals on Avia are actually low frequency signals sent to the main speakers that get pushed to the subwoofer through bass management. This is useful for setting the subwoofer for bass management, but it does not allow one identify and fix problems found when the LFE level is incorrect relative to the subwoofer level for bass management.

The following procedure can be executed without a sound pressure level meter. You will use your ears to balance the channel levels instead. That is not as bad as it might seem since these devices are just a way of putting a number to what we hear anyway. The biggest negative is your system will not be set to reference at 0db, but it should be balanced better than any automated calibration system I have seen. Inexpensive SPL meters or microphones found in automated calibration systems are frequently off by 3db or more from reference anyways. Using an SPL meter does make balancing the subwoofer easier. When setting the subwoofer level without a meter you will need to listen to a variety of music with heavy bass and a combination of dialog to get a reasonable level for the subwoofer. When checking for the LFE bug pay attention to how loud the subwoofer test is with Avia compared to the signal on Goldline and be sure to set the receiver/preamp volume as recommended for each of those DVD’s appropriately.

Test Requirements:

• Acquire the Avia DVD and Goldline Toolkit 5.1 test DVD. Do not use Digital Video Essentials the test tones on that product and many others including those built into receivers and preamps are wrong and inadequate.
• Be sure to set your volume to 0db or whatever is considered reference on your product when you use Goldline and -10db when you use Avia so the test signal is always 75db. Relative and absolute volume control level is sometimes selected in the setup menu. The use of relative volume is useful to understand where the receiver is set relative to reference level and to get an idea of the headroom available in your amplifiers. Using a -10db setting for Avia keeps the volume from being excessive to work in and will make the level of the test signals 75db for both Goldline and Avia.
• Turn any fans in the room off and the heater or air conditioner off if it creates significant air movement at the primary seating location like a duct blowing on a measurement location.
• Make sure the background noise is no greater than 65db on your meter. If it is you will need to run the test tones about 10db higher than the background noise instead of the 75db suggested below. Sound levels above 85db are not recommended. To do this the volume control needs to be raised above the recommended level of -10 for Avia and 0 for Goldline. Every 1db increase in the volume setting will increase the target value for the SPL meter by 1db.
• With a 6 or a 7 channel surround system you should engage either Dolby EX or Dolby Prologic II Movie mode anytime you need to measure the back channel speaker levels. With a 5 channel or less system you should set the system to a straight mode or one that shows Dolby Digital on the front of you receiver. Do not use a Pure Direct mode because this will bypass bass management and invalidate some of the subwoofer tests.
• Using the Avia DVD check your setup to make sure every speaker is getting the signal it should. These tests are found under Advanced Avia from the title menu and in the Main Speaker Setup chapter under Channel Identification Test. If there is a problem make sure you are using an audio connection from your DVD/Blu-Ray player that will carry all of the channels. Also check that the receiver/preamp configuration matches your installation. Speakers that do not exist should be turned off in the configuration.

Avia Main Speaker Setup Menu

Check Speaker Phase:

• Set the receiver/preamp volume to -10db.
• Put the receiver/preamp in a straight audio processing mode so you see Dolby Digital on the front of the receiver.
• Play the speaker phase tests on Avia in the Main Speaker Setup Menu.
• Listen for the speakers to be in phase following the instructions on the DVD. When setup properly the in-phase signal should sound focused between the two speakers being compared and the out of phase signal sounds diffuse. If this is reversed one of the two is out of phase with the other.
• Swap the speaker wiring on as few speakers as possible to correct any phase error found. This is done by comparing multiple speakers and determining which combination of speakers fail the test. Phase errors are not just the result of external wiring errors, but are also found from internal wiring and logic errors in speaker and electronic products. Always power down your amplifier when swapping speaker wires and be sure not to short out the wiring.

Avia Subwoofer Setup

Check the Subwoofer Phase:

• Set the distances in the receiver/preamp setup menu to be the actual distances from your primary listening position for each speaker/subwoofer.
• Plug the cable from the receiver/preamp into the input labeled LFE if available. Always power off the subwoofer when making or breaking the connection to it.
• Set the crossover on the subwoofer to maximum Hz or bypass if available.
• Set the subwoofer phase to 0 degrees.
• Set the subwoofer polarity to positive or 0 degrees.
• If there is no polarity or phase switch you will need to reverse the speaker leads on the speaker used for the test. If the best subwoofer phase is with the speaker wires reversed from that determined in the speaker phase test above all speakers will have to have their wiring reversed to bring the subwoofer in phase with them. If you do not measure a change in SPL when the phase or polarity on the subwoofer is changed that may indicate these are not functioning properly on your subwoofer and you should try swapping the speaker wires as if you do not have these switches.
• Set all the speakers to small and a crossover no lower than 80Hz (speakers with woofers smaller than 5″ typically require a crossover setting greater than 80Hz) in the receiver/preamp setup. This is required for the phase test for the subwoofer on Avia to work properly.
• Set the low pass filter for the LFE channel to 120Hz or greater.
• Set the receiver/preamp volume to -10db.
• Put the receiver/preamp in a straight audio processing mode so you see Dolby Digital on the front of the receiver.
• Play the subwoofer phase test on Avia in the Subwoofer Setup Menu.
• You can use your SPL meter instead of a second person to find what phase setting on the subwoofer results in the loudest signal level which will be the best choice for the phase setting. Phase errors are not just the result of external wiring errors, but are also found from internal wiring and logic errors in speaker and electronic products.
• Raise the level on the subwoofer if it is too low to show any difference between in and out of phase.
• Lower the level on the subwoofer if it is too high to show any difference between in and out of phase.

Measure & Set Main/Center/Side Surrounds Channel Levels:

• Set the receiver/preamp volume control to -10db.
• Play the limited band width pink noise level test signal for each speaker individually found on Avia. These are found under Advanced Avia from the title menu and in the Main Speaker Setup menu.
• Measure the SPL level with your SPL meter set to C and Slow at the location where your head would be for the prime seat.
• Using the Radio Shack meter it is very important to point the instrument at the speaker. This compensates for the instrument being very directional in nature. This can be seen by the large size of the diaphragm. Diaphragms that are 1/2″ or less should most likely be mounted vertically if you have a different instrument.
• Adjust the corresponding channel level in your receiver until the level reads as close to 75db as possible on your instrument when playing the test tone from the DVD.

Goldline Acoustic Tests

Measure & Set Back Surround Channel Levels:

• Set the receiver/preamp volume control to 0db.
• Measure the level of the right side surround channel with the receiver/preamp built-in test tone.
• Set the back channel(s) level using the same internal tone to match the right side surround level to the value measured.
• Measure the back channel level using Goldline Toolkit 5.1 DVD Back Channel Acoustic Test Signal (Title1:Chapter 5) and set it to 75db. If you have two back channels move both right and left channels equal amounts until you hit 75db. When using a radio shack meter point it at the center between the two back speakers.

Verifying Speaker Levels:

• Set the receiver/preamp volume to 0db.
• Sit in the primary chair and play Title 1:Chapter 9 narrowband test for L-C-R-Sr-B-Sl. Try and match all of the channel levels as close as possible to the left front channel. Make sure in a 7 channel system that the back channel sounds centered. It is common for speakers behind to sound low and need to be elevated because we do not hear as well to the rear.
• Check each seat in the theater and lower the surround level if necessary to avoid it being too loud in any seat considered important.
• Repeat the test at the primary seat and alternate seats until a reasonable balance is obtained.

Set Subwoofer Level:

• Set the receiver/preamp volume to -10db.
• Set the subwoofer level in the receiver/preamp setup menu to 0db.
• Set all the speakers to small and a crossover no lower than 80Hz (speakers with woofers smaller than 5″ typically require a crossover setting greater than 80Hz) in the receiver/preamp setup. This is required for the level test for the subwoofer on Avia to work properly.
• Go to the Subwoofer Setup Menu on Avia and play the limited band width pink noise level test signal from Avia.
• Measure the SPL level with the meter set to C and Slow at the location where your head would be for the prime seat.
• Point the meter at the speaker from the location where you head would be at the prime seating location.
• Adjust the volume on the subwoofer until it reads 75db with the Avia test signal. If you cannot get to 75db with the volume on the subwoofer use the channel level in the receiver/preamp. Do not set the subwoofer level in the receiver/preamp lower than -6db to avoid problems with the auto on in the subwoofer. Do not set the subwoofer level in the receiver/preamp higher than +3db to avoid problems with overloading the circuitry in the receiver/preamp or the subwoofer.
• Set the receiver/preamp volume to 0db.
• Play the Goldline LFE test signal Title 1: Chapter 7. If this is 10 to 15 db lower than 75db you have something known as the LFE bug in your equipment. This means the LFE (low frequency effects or rumble) will not be loud enough. This can sometimes be corrected by changing a setting in the receiver/preamp for the LFE signal or changing the data type coming in or the processing mode in the receiver/preamp or firmware in the receiver/preamp. The data type coming into the receiver can be changed in a Blu-Ray player by selecting LPCM instead of Auto or Bitstream for the HDMI audio data type. PCM over coaxial or optical will not fix this, but instead result in a complete loss of the LFE channel. You should recheck the channel levels if you change the data type because they may shift by 4db from changes in how dialog normalization is handled in the player versus your receiver.

Set Speaker Crossover Frequency and Verify Subwoofer Level:

• Set the crossover frequency for your speakers based on woofer size:
  • 12″ or greater – 40Hz
  • 10″ – 60Hz
  • 8-5″ – 80Hz
  • 4″ – 100Hz
  • <4″ – 150Hz
• If your subwoofer is small relative to your speakers it may be best to set some of the speakers to large instead of small. The larger your subwoofer the more likely it is beneficial to push more sound into it instead of the speakers. This unloads the amplifier for the speaker and distributes the low frequency energy into the product most capable of handling it.
• If your subwoofer is closer than 6 ft from your primary seat and not close to the center speaker it may make sense to lower the crossover setting for the center channel speaker to avoid hearing dialog coming from the subwoofer.
• Listen to a mix of music heavy in bass along with male and female dialog to determine the best setting for subwoofer level and crossover point. Experiment with a change in crossover frequency around those recommended above for the main speaker and center speaker. Choose the frequencies that result in the best overall sound quality. It may also be necessary to raise or lower the subwoofer level a few db to achieve a better level of bass overall in the system.