Reference level is playing back a movie at the same level as it was recorded, basically. For HT, you would calibrate for this with a setup disc and an SPL meter. The loudest ref level for DD is 105 db at the listening position. Not all movies will get that loud. - C
Mentioned in the FAQ AND PRIMER which is linked in the opening of this forum and in my signature: http://www.hometheaterforum.com/htfo...553#post650553 -Vince
Also remember, besides reference level being just damn loud, a lot of systems aren't capable of reference level. A fair number of systems have speakers that are capable but few have subwoofers that are capable of reference level. I personally listen at 10dB below reference with my sub 2-3dB above this level.