Its true to a degree. Any equalization system can adjust the tonal qualities of a speaker and thats exactly what auddessey is...a complex software based EQ system.
From what i understand from reading the Auddessey website, Auddessey is designed to tame the brightness inherent in a lot of speakers out there while also boosting bass frequencies to adequate levels. Its supposed to even out the treble to bass ratio. Doesnt always work as advertised though, but it can get pretty close. Your best bet is to purchase the speakers that get the closest to the tonal qualities you like without equalization, then use auddessey to fine tune it based on your space.
Auddessey has a couple of different settings that treat the treble/bass ratio differently, so you arent stuck with just one setting. The standard "Auddessey" setting tames the treble while boosting bass somewhat. "Auddessey Flat" is supposed to simulate a flatter response which probably means less treble cutting and maybe less bass boosting, but this will depend on the combination of your speakers and the room they are sitting in.
On my system (Denon AVR 1912) in my room, i have found Auddessey Flat somewhat better for music, while the standard Auddessey setting was better for movies.
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