Yesterday we explained how to determine what your "reference level" is based on your master volume setting on the receiver.
Today, a few comment on why this information is important.
First, let us remember that at reference level a home theater system will require each main channel to have 105dB of headroom and the subwoofer(s) to have 118-121dB of headroom. This assume all speakers are set to small with the deepest bass from all the main speaker combined and sent to the subwoofer(s) along with the LFE channel. Also, the term "headroom" simply means clean output capabilities at the MLP(main listening positions).
If you want your system to have the ability to reproduce full reference levels with the most demanding source material you should factor in another 3dB of headroom for each channel. This way you won't be at the absolute limits of the system which will often cause various distortions and an overall degradation in the quality of the audio presentation.
Now, reviewing the above information we can quickly determine the performance requirements for a given headroom "target". For example, if you rarely/never use master volume settings louder than 10dB under reference level we can safely say your main speaker should be capable of clean 98dB peaks at the seating and the subwoofer should be capable of 111-114dB peaks.
Once we know this information then we can examine variables like the room environment, intended subwoofer placement, distance from the speakers/subwoofer(s) to the MLP, etc and accurately determine the best subwoofer(or speaker) for your needs. Or, we can determine if you even need to upgrade from your current products. You may have all the headroom needed based on your listening preferences..
Power Sound Audio