Well it has taken awhile but i finally remembered to check out the SPLs in and out of the HT room.
With the Spirt of the West playing, i had in room peaks around 95dB at the 10-12 foot mark. The Onkyo 797 was set at 75% on the volume knob (0-100 absolute scale).
Outside of the room, with the doors closed, SPL fell to 69dB about 8 feet from the doors.
On the opposite side of the HT wall in the utility room, SPL measured 67dB.
Still quiet enough for an easy conversation.
One floor up in the living room (directly above the HT room), SPL measured 62dB but at this point, it was really only bass sounds that were setting it off. The music was not clear and with any amount of sound (e.g. the family room tv playing) the music in the basement was almost negligible.
Upstairs on the second floor, only a vague bass thump could be heard inconsistently.
The bottom line, media rooms do not need thousands of dollars of high tech gadgetry for sound control. Reasonably good wall design, sound insulation and in-room furniture for sound energy absorption goes a long way.
A decrease of over 30dB one floor up puts the sound into a range of easy conversations while the media room is blasting away. This is VERY acceptable IMO. Bass will always be the hardest sound to control and contain.
