Originally Posted by NicolasKL
Huh? You can't hear anything below 60 or 80 Hz? Then why have a sub? I assume you mean it shouldn't be obtrusive or localizable but to say you shouldn't hear it is just wrong. If you're hearing audio significantly below your crossover, then you're hearing your sub.
Nikolas - A sub-woofer by definition should reproduce the lowest octave of music (20hz - 40hz). An extremely good sub-woofer can produce sub-sonic frequencies (14hz-16hz). To acheive this usually demands a very dedicated driver, a fairly good size enclosure, and dedicated electronics. Back in the late 1980's / early 1990's, I had a Janis sub attached to a Carver amplifier (375 watts stereo / 750 watts bridged mono) that could acheive the levels referrenced above. This was used in combination with speakers from Dahlquist / KEF / DCM / Quad / Vandersteen and electronics from Audio Research / Conrad Johson / Carver. I used an electronic crossover set at about 65hz so the amplifier would never see any output above that frequency. If you get a chance to hear a sub like that, you will understand what I am talking about when I discuss the so called sub-woofers that are generally used for home theater. Most of these just woofers. Some are good to extremely good, some leave a lot to be desired. I have heard many home theater systems including my own, and with test tones and a sound meter, most have outpu down by 10-20db when you get to 30hz. This means that the bass roll-off of the driver/enclosure starts somewhere between 40hz-50hz.
I am using a Yamaha sub with my Vizio sound bar now. The Yamaha has good output to about 40hz and rolls off dramatically after that. Does it sound good. I think so. I believe it adds just enough fullness to complement the Vizio sound bar for most of the frequency and dynamic range for home theater.
I still use a Boston Acoustics sub with my main stereo. The BA is good down to about 25hz in my current set up. My equipment tastes are much more modest these days as I live in a 1700 sq. ft. condo. In my former home, out family room measured 25 x 35 with 10' ceilings (approx. 8750 cu. ft), and could handle a much more robust system. Actually, I don't believe I currently have a long enough wall to play a frequency below about 25hz. I used to have a chart showing the length of various soundwave frequencies. In many cases, the lowest frequency that can be reproduced in a given room is determined by the room itself. Example, in a 12x16 living room, you can not physically have a soundwave less than about 32hz.
When you see specs for home theater showing a sub with output to 20hz, be sure it shows at what db level the measurement is taken.