Audio technology has come a long way since the early 1900’s and this can be seen by the size of the Denman horn, which is a massive 27ft long! When this horn was built, it produced incredible quality audio and it still does considering how long ago it was built. Even though it was built all that time ago when sound equipment wasn’t great, just a little knowledge of some basic acoustic principles meant that this horn could be made. Nowadays we have many ways in which we create high quality audio, particularly in smaller and smaller enclosures, but the same basic principles used back in the 1930s are still in practice.
Horn loudspeakers work the way they do because they create a greater pressure around the speaker cone, which is the same effect of putting your guitar amp in a corner. When a sound source is placed on the floor, the area in which sound can propagate into is halved (assuming it propagates in all directions evenly and cannot propagate into the ground), meaning that the sound pressure is doubled. This effect happens again when you place it against a wall and again when in a corner, hence if you want the best response (particularly bass) from your guitar amp, then stick it in a corner. As the horn surrounds the speaker, the sound pressure in massively increased and sound level becomes greater.
The gradual flaring out of the horn is used to slowly match the pressure around the speaker to that of the natural environment, reducing unpleasant audible effects that this could cause otherwise. As length of the horn increases, the low frequency response increases, due to the longer wavelength of low frequencies (a greater distance between their sound compressions).
These methods can still be used today, but are altered into a smaller context, or are implemented in a different way, often taking advantage of the resonant frequency of a speaker enclosure, in an attempt to boost the signal. Nowadays a more common method is use of a vented box (a speaker with a hole in the front). Even though we no longer have to have a 27ft horn in our house to get high quality audio, there are still many things we can learn and use from audio methods of the past like the Denman horn.
What do you think of this, would you still want a music player in your house if it was the size of the Denman horn?
 BBC News Article – http://www.bbc.co.uk/news/uk-27483035