•THX setup sends you to a screen in which you can configure some THX- specific features.
Specifically:
•THX Ultra 2 sub should be engaged if you are using a subwoofer that is certified by the THX Ultra 2 standard. Such subwoofers are essentially flat to 20 Hz under what might be considered worst-case acoustic conditions for bass, and have prodigious output capability. If you select the THX Ultra 2 sub button, you will also notice that the otherwise grayed-out boundary gain compensation button becomes available. (See below.)
•ASA stands for Advanced Speaker Array, and engages a proprietary THX technology that provides outstanding flexibility and performance in your surround sound array. This button will take you to a submenu in which you specify that your rear speakers are together (less than 1 foot apart), close (between 1-4 feet apart), or apart (more than 4 feet apart). In an ASA surround system, the ideal situation is one in which the rear speakers are almost touching each other, and you have selected together. This allows the ASA processing to create the most seamless and versatile surround sound field.
•boundary gain compensation will adjust for the fact that most of us do not suffer from the worst-case acoustic scenario that THX Ultra 2 subwoofers can handle. If you have such a subwoofer, and it is placed within 3-4 feet of at least one wall, engage the boundary gain compensation. It will correct for the acoustic reinforcement your room is providing to the subwoofer in order to yield the flattest, most accurate bass.
•positions 1-4are the menus in which you can create and recall families of speaker level and distance measurements for later use. You might have one position defined for the seating arrangement used for standard movie viewing, and another for when you are sitting by the window reading a good book.
Positions can be enabled or disabled as required by going to the system setup/speakers/position menu. If the position in question is highlighted, it is available for use. If it is not highlighted, it has been disabled to prevent accidental use.
