Only desired, and used on two receivers in 2 different rooms of my house, for all day background WAV. ripped music, because their SPL`s are roughly run at around conversational level, and by doing so, balance`s out the tonality of the garage, and spare bedroom that I have these receivers in, even with passive RS dual voice coil 12" ported sub woofers in use, and the bass is not boomy with the loudness engaged, or I wouldn`t turn it on.
I feel that I`m using the receiver`s loudness button, in the manner/reason for which it was originally created and the sound is much fuller for it.
All the rest of my house`s room`s sound system`s don`t require loudness to be engaged, as they utilize much better, & bigger speakers/powered subwoofers + a lot more total wattage is available, and when their turned on & used it`s not for background music purposes..