Hand-waving: At 80 Hz a wavelength is about 14 feet (169", 4.3 m). Your ears are maybe 8" apart, or about 0.047 of a wavelength at 80 Hz (a delay of about 0.6 ms). At low frequencies the wavelength is so large relative to our head that the sound appears to arrive at both ears at (nearly) the same time, making it difficult to impossible to resolve phase differences, so we lose the ability to determine direction. Our hearing sensitivity is also much lower (look up equal loudness curves and see how much louder 80 Hz needs to be to be heard as loud as 1 kHz).
See e.g. https://en.wikipedia.org/wiki/Sound_localization
for a discussion of ITD and IID (time and intensity differences used to determine direction) and some of the math describing how small an difference we can localize. At higher frequencies, we can resolve down to the microsecond level, but at low frequencies wavelengths are too large to distinguish direction. From the Wikipedia article:
"The lowest frequency which can be localized depends on the ear distance. Animals with a greater ear distance can localize lower frequencies than humans can. For animals with a smaller ear distance the lowest localizable frequency is higher than for humans."
HTH - Don
I have the following problems with this explanation:
1. At 160 Hz, the wavelength is 7 ft, and at 320 Hz, the wavelength is 3.5 ft (still wider than the human head), etc, so at what frequency range would this hand-waving explanation predict one's ability to localize the direction of the sound?
2. The speed of sound is constant, so sound will appear to arrive at each ear at nearly the same time, regardless of frequency.
3. If the lowest note on a double bass is plucked by a player standing on your left side, would your hand-waving explanation suggest that you would be unable to localize it?
Interesting history about the choice of 80 Hz for crossover: https://twit.tv/shows/home-theater-geeks/episodes/1
, specifically 20:50-22:30 or so. Tomlinson Holman also discusses it briefly in his book Surround Sound, second edition, which I don't have available right now, but I don't remember him mentioning the detail about Swedish radio there.
Griesinger's video (well-respected, developed Logic 7, used to work at Harman, mentioned in Toole's book and many articles about concert hall acoustics) is worth reviewing.
In our home media room, we have two subwoofers, currently used with Dirac correction up to 400 Hz. Our setup would not allow for mid-front and mid-rear wall positioning, so I have one on each (nearly) mid-sidewall--I found the node for the first length mode for each wall, which is a little different because of the position of the entry door and equipment closet door on the left side, and split the difference for symmetry purposes. This way, a la Toole and Welti, the subs do not excite the first length mode and actively cancel the odd-order width ones. Is there such a thing as stereo bass? Welti doesn't believe in it (https://hometheaterhifi.com/technic...n-interview-with-todd-welti-and-kevin-voecks/
), Griesinger says yes, @Matthew J Poes
discusses here: https://www.audioholics.com/room-acoustics/stereo-bass
. I actually have the subs as stereo for the possibility of contribution to the perception of spaciousness or spatiality when stereo bass content is available, otherwise most bass content is likely to be mono, anyway, and I'm using bass management, so what's the harm? This setup with the wider subs may also take advantage of Blumlein shuffling. In addition, I have several PSI AVAA C20s, so it's my eventual plan to do more home listening tests and comparisons, along with some measurements--part of my endless to-do list.
I do like seeing different ideas.
That was my main purpose in participating here. Instead of considering amplitude/phase (EQ/delay) correction versus electroacoustic damping, you might be interested to read about Dirac Active Room Treatment, which promises to combine the best of both worlds: https://www.dirac.com/introducing-dirac-live-active-room-treatment/