"Voiced" can be an expression of getting it right in the surroundings it’s in. whether it be bass mids or treble or combinations of all.
Moving a sub back and forward in a room to get it phased right to the mains is also call "voicing".
It can measure flat in an anechoic chamber, but then has to be "voiced" for domestic situations (eg: next to a floor).
So I stand by what I said above, that a good sub that’s designed to sit on the floor will be "voiced" to sound right (flat if you wish). By raising said sub high off the floor may be counter productive to it’s designers "voicing."
BTW if you put Roys’ designed corner speaker out into the middle of the room they had no bass, they were "voiced" to get reinforcement from the room and or floor boundaries. And others like Bose with their shocking 901 had no bass if they weren’t near and facing the wall, and their are many others as well, Linn Isobarics etc, all "voice" to be next to a boundary whether wall or floor.
So a good designed subwoofer will sound it's best where it was designed to be, not 10' off the floor.
Cheers George