It takes a large transducer (speaker cone) moving back and forth to create a low-frequency pressure wave with enough amplitude to move our eardrums. The larger the speaker, the better chance it has to create those big waves. That’s why PA systems at live events use large subwoofer speakers with extra large cones, 18″ is the standard as well as some form of horn loading to increase efficiency. Consider how much sound wave will be created by such a large cone, and you’ll understand why most small speakers operating in open air, like those on your phone or laptop, can’t put out a lot of bass.
Then how the headphones generate bass with their puny cones? That is because unlike loudspeakers, headphones aren’t operating in open air! Headphones, especially the in-ear types, create a closed “tunnel” between the speaker and your ear. Relatively little air can escape from this tunnel, so your headphones are basically directly coupled to your eardrums, making them very efficient. An in-ear monitor sealed into your ear canal couples very well with your eardrums, and produces plenty of bass despite its small size. Open-back headphones may not seal so tightly, but they’re typically loaded with larger headphone drivers (usually 40 or 50 mm) and are able to move plenty of air down the ear canal.
First think first, LFE track is designed to be fed to a loudspeaker. It is an audio track. Secondly, it is monitored in a film post-production studio by ear, hence it should have the range of signal that can be heard in a 15m average room where response down to 8Hz was not available. Why do you want an octave lower response in your room then the makers of the sound track had?
I am an electroacoustic engineer with a M.Sc. I have designed a commercial speaker. I worked in music and sound track production as a a recording engineer.
I have four identical 15" closed box subwoofer at each corners of my HT, which is 8m by 5m. Each measured to have their fc @ 22Hz. That means I should be able to reproduce below 20Hz with the help of the boundary boost. I can verify that with an SPL meter.
Hence, I can assure you that I know what I am talking about and I also have the set-up to test that on.
Like in a headphone, the sound in a car does not work like on open air. There is a lossy tunnel between the speakers and your ear. However, as the tunnel is lossy you need much larger low frequency energy on low frequencies. That is why you need disproportionally larger subwoofers in cars.
I think we were not on the same page here, as your write up there had nothing to do with the initial discussion/my question, but I'm sure the info you presented will be useful to someone who comes across it, since it's good general info, so it was not in vain.
You stated 8Hz can't be reproduced inside a room with its largest dimension being smaller than a quarter of the wavelength of the frequency (physical relationship). That's what my question was directed to, because that statement doesn't make sense to me.
"Why does the wavelength need to fit inside the acoustic space?" would be my question. Not "Why is is harder to reproduce bass outside than it is to do so inside a closed headphone?".
Regarding the example of your listening room: You say your room is 8m wide/deep(?), so according to your previous claim, it's impossible to reproduce frequencies of a wavelength longer than 4*8m=32m, which equals to 9Hz and below. You say you "should" be able to reproduce below 20Hz, but 9Hz is a long shot from 20. Hearing threshold of 9Hz is ~99db, your setup is a good starting point to get there, depending on the drivers used, albeit probably not with low distortion. Typically you see those chasing sub 10Hz response with setups like 8 21" drivers or more. I've seen a "home" theater with 24 24" subs...
Lastly, to answer your question as to "why", there is an entire community around it and the main term would be "BEQ" or "Bass EQ".
1000+ pages and 1million+ views.
500 pages and 500k views.
They basically analyze the response of an entire movie and then EQ it to target.
Hundreds of people have built systems to either reproduce frequencies below 10Hz acoustically or mechanically (the latter mostly, as it's way easier to achieve and doesn't come with the penalty of sounds your neighbours will hear), to get the tactile aspect I was talking about. Why? Because it's awesome. I had my couch on a riser with tactile transducers taking care of frequencies between 10 and 25Hz (not lower because it wasn't capable enough; it does not produce sound, only vibrations). EQ'ing movies/games/"content" can be hit and miss, since these frequencies are typically not properly mixed/taken good care of like you pointed out, but most of the time it adds a to a great experience.