To get the best performance from your surround system all of the following elements must be done properly. It is amazing how good even a modest home theater can sound if it is setup properly. You cannot rely on the automatic setup function found in the receiver or your installer to do this properly. I find these mistakes in even the most expensive theaters in the country.
- Verify every speaker in your system is really working in your system. You need to use a test DVD or Blu-Ray that will step through each channel. Telling the receiver you have rear speakers is not enough to be sure they are actually used. Modes like Prologic IIx are required and other settings may also be required. Testing this with the Goldline DVD is the best way to verify your system is using the rear speakers.
- Verify every driver in each speaker is functioning properly by listening to wide-band pink noise. Tweeters are the most common failure point. When defective they will buzz or the sound will be dull. Many errors can occur in assembly and transit. In a 5.1 system I find around 20% have at least one failed or loose driver.
- Verify each speaker and subwoofer are in-phase to ensure they do not interfere at the crossover. Simplistically this is matching the red and black terminals on the receiver and speakers. The problem is many subwoofers and speakers have this wrong internally so the black and red or polarity switch are frequently wrong. A real time analyzer can be used to detect the problem and an absolute phase meter with test tones will also help get it right. When this is wrong things like bass guitar and drums will sound weak. I find about 50% of systems have at least one speaker wired out of phase from the factory with the subwoofer being the most likely to be wrong.
- Eliminate 60Hz hum from subwoofer. Ground loops frequently cause a 60Hz hum from the subwoofer. Using the proper volume on the subwoofer can help with this and eliminating the source of the ground loop will as well. Common sources of ground loops are cable signals and poor electrical grounds.
- Match speaker and subwoofer levels. This is difficult to do well because almost all of the receiver test tones are poor. The best method for setting speaker levels is to use the Goldline Audio Toolkit 5.1and match the band limited pink noise by ear. The reason for this is that the ear functions differently than any test microphone. You also need to verify that the level is not irritating at any seat commonly used. Subwoofer levels are best set at the subwoofer with 0db level on the receiver. This will ensure the subwoofer amplifier is operating near a reference voltage level enabling the automatic on/off circuit to work properly. -9db for example on the subwoofer output from the receiver will drop the voltage to 1/8 the normal level. When this is wrong your system will not sound seamless. You should not easily be able to identify which speakers are in use at a given time. Subwoofer levels are best set with a real time analyzer. When balanced properly drums and bass guitars should sound good and movies should rumble nicely with little distortion.
- Bass management crossover frequencies should be optimized for your speakers. Typically I would recommend 80Hz for speakers with 6″ woofers or larger. Smaller woofers will typically require a higher crossover frequency. Note the subwoofer also has a crossover that should be set a the maximum frequency (Hz) when the crossover is done in the receiver. Verify this by listening to to wide-band pink noise on each channel. This needs to be correct in both the receiver and the source.
- Low pass filter for the LFE channel should be set to 120Hz. The LFE channel contains information up to 120Hz and should not be more heavily filtered.
- Disable all range compression features in receiver and all sources. These will be labeled something like night mode, DRC, fixed volume. Missing some of these will dramatically reduce the sound quality.
- Eliminate poor audio processing in preamp and sources like up sampling audio data. Listen to quality audio to confirm which of these options is the most neutral. Poor processing choices can add aliasing to data along with other problems.
- Timbre match the speakers. You want each speaker in the system to sound similar. This is most important for the front mains and center. This is best done with a quality microphone and a real time analyzer using wide-band pink noise. It is important to eliminate annoying frequency problems. Doing this will dramatically improve the sound quality for even modestly priced speakers. Your system should come close to SMPTE 222M when this is done well and just sound right with dialog easy to understand.
- Optimize subwoofer performance. In a reference theater this would involve acheiving flat frequency response from 20Hz to 120Hz. If you do not listen at reference levels it may be best to boost the bass from 20Hz to 30Hz to recover some of that lost rumble if you own a subwoofer that can go that low. A combination of reference material and a real time analyzer are the best ways to get this right.
- Be certain to listen near reference (0 to -5 db). Many people listen way too quiet obtain quality sound. Many systems will not be able to handle reference levels for all channels for all source material, but most quality systems should handle -5db from reference.
Doing these things properly is very complex . Your choices to do this are to hire a professional calibrator like AccuCal with $40,000 worth of gear, purchase test equipment to do this yourself or adjust it to what sounds right to you.