Check the basic settings in your home theater system on a semi regular basis.
Often, these settings may change without you even knowing if you have any components that do automatic updates or even if the AC power to your home is interrupted.
In the receiver, verify your speaker settings are correct. In nearly all scenarios it is best to have all speakers set to *small* with a crossover (highpass) for all of them set no lower than 80hz. This assumes you have a quality subwoofer(or two) in the system. If you have a SPL meter, double check the channel calibration levels. If you have your receiver doing video up-scaling for you look over the settings there as well. Be sure you get maximum benefit from the available options.
For any video source components(DVD player, Blu-Ray, even an old SVHS or Laser Disc) ensure they are all set for maximum video resolution supported by your display. While you are at it check that the aspect ratio selections are correct for each device. If your receiver offers "up conversion" for the video resolution experiment with the settings in the source device and the receiver to see which provides the best picture quality.
On the audio side of things check the output options for each source component in your rack. We have had instances in the past with a Power Sound Audio customer enjoying great bass on some source material and weak bass on other discs. Through a bit a troubleshooting we eventually narrowed it down to the DVD / Blu-Ray player sending only a two channel signal(often labeled *PCM*) to the receiver instead of the full 5.1 audio(often labeled *bitstream*). So the receiver would "matrix" the 2.0 signal to surround but it would have no LFE channel. With some movies this may sound okay, with others it would sound very weak(in the bass). It would be dependent on how much of the LFE bass was duplicated on the main left/right channels by the sound engineers involved in the production process. While in the DVD/Blu-Ray menu also check that no type of "dynamic range compression" is enabled. This has also popped up in our troubleshooting in the past.
Last but not least...read the owner's manuals for your audio components. Hey, you often pay hundreds if not thousands of dollars for each item in your equipment rack it only makes sense to spend a few minutes reading each manual to ensure optimal performance, right?
Power Sound Audio