If you like horns...

OldSchoolPolk · February 2019

This is a surprisingly clear explanation of how horns work. I don't know how accurate it is but it helped me understand the concept

.world's largest horn shatters glass

OldSchoolPolk · February 2019

OK, so it's obvious I'm inept at attaching links from Youtube, Let the laughter begin. But if you try that phrase in Youtube you should find it

agfrost · February 2019

Apologies, your post led me to this place...

agfrost · February 2019

Here's a hand with your link:

https://www.youtube.com/watch?v=pFEB0chiuJA

mhardy6647 · February 2019

I just went in a big circle.

I reckon this is the YT video to which the OP was referrin'.

https://youtu.be/pFEB0chiuJA

Horns are simple enough in principle, they're acoustic transformers (impedance matching devices).

In practice -- to make one that is well behaved across a broad range of frequencies... that's (still) a challenge!

mhardy6647 · February 2019

The red horn on that video isn't particularly large; there have been numerous "room sized" horns built for hifi over the years. Steve Deckert at Decware turned a basement into a bass horn --- and cracked the foundation due to a problem with standing waves or resonance in the process

Here's another 'crazy basement horn' (clickbait type of link, for which I apologize):
https://gizmodo.com/horn-subwoofer-takes-up-crazy-mans-entire-basement-5025867

Nelson Pass's ironically named Kleinhorn (small horn auf Deutsch) is/was... well... moderately large. Probably about the same size as the one in the YT video, given the area of the mouth.

https://www.passdiy.com/project/speakers/the-kleinhorn-part-1

Those Lowther drivers are nominally 8 inches in diameter, to give a sense of scale (or you may notice a tt on the shelf).

mhardy6647 · February 2019

the problem is that the speed of sound is fairly slow, so the wavelength of bass tones is pretty long. The wavelength of a 20 Hz sine wave (tone) is 56.5 feet.

Thus, if one wants to make a horn with good performance at low frequencies, one usually folds the horn (like the Kleinhorn above, or the famous Klipschorn folded corner horn).

Here's a straight 30 Hz (wavelength 37-2/3 feet) bass horn (well, a pair of 'em, by the looks of it).
http://vincent.brient.free.fr/bass_horn.htm