Will respectfully disagree Cajundaddy. Most modern floor standing speakers go well below 50hz with little/no rolloff. My Focal Aria 936’s are -3db at 38Hz as I recall. Like many, I integrate (hi level) an REL sub that blends in and goes down to about 25Hz.
The benefit is not to necessarily “hear” the sub (when properly integrated you don’t hear it at all) but rather to pressurize the room with harmonics that are missed otherwise. It makes the SQ so much more palpable and rich, even in mid-range frequencies. And of course Toccata and Fugue in D minor will shake the foundation on a good recording!
