The Talking Machine Forum — For All Antique Phonographs & Recordings

So, whenever I demonstrate a cylinder phonograph at the museum, I like to slip the rubber connector off the reproducer to show the difference. I know that the horn does not really increase the volume, but you have to admit, it does seem to do just that.

I usually tell people that it is like when you cup your hand near your ear things sound louder, but they really aren't.

Is there a simple, easy to understand way to explain what horns do for the volume, or perceived volume as it may be.
Thanks!
Dave D

My layman's guess is that the horn lets the sound develop and increase as it reaches the outer edges of the horn and into the room. They recorded the acoustic records in the reverse, capture the sound and then it increases due to the smaller opening at the recording head, without the horn neither would happen.

It does amplify, it's to do with pressure through the cone in exactly the same way a trumpet or tuba amplifies the sound of the mouthpiece into something very loud

https://en.wikipedia.org/wiki/Horn_loudspeaker


Edit: yes my use of the word "amplify" was technically wrong - it transforms the wave into something with greater acoustic power

mick_vt wrote:It does amplify, it's to do with pressure through the cone in exactly the same way a trumpet or tuba amplifies the sound of the mouthpiece into something very loud

The horn doesn't amplify.
Amplification suggests that there is more power at the output of a device than there was at the input of the device.


If you are interested in horn theory and how they work read the chapter on horns in "Modern Gramophones" here:

https://archive.org/details/ModernGramo ... 9/mode/2up

This book was published in 1929, not an easy book to find but a must have for your library.


Chuck

The horn simply transforms the (high intensity * small air mass) at the throat into a (lower intensity * greater air mass) at the flare. I believe it is in the Victor & victrola page where they explain this phenomenon using an example with kicking pool balls, very illustrative.
In fact, the horn has an energy loss along its length, as does any energy path.
If you make a narrow and long paper cone with a small flare and play your records thru it, you'll notice how intense the sound is in the axis of the horn, almost unbearable. But it cannot move the air in the room. The trick is the exponential horn. Narrow and long at the start, it distributes the energy at a slow pace, to a wider mass of air as the waves advance along it. Once more mass of air has acquired the vibratory energy, the flare can be expanded at a higher rate. This happens at each infinitesimal slice of the horn perpendicular to the central axis.
The best one, the tractrix horn, expands until the flare opens at 90 degrees at each side, forming a plane baffle from which the sound radiates into the room.

"An acoustic horn converts large pressure variations with a small displacement area into a low pressure variation with a large displacement area and vice versa. It does this through the gradual, often exponential increase of the cross sectional area of the horn."

"The horn serves to improve the coupling efficiency between the speaker driver and the air. The horn can be thought of as an "acoustic transformer" that provides impedance matching between the relatively dense diaphragm material and the less-dense air. The result is greater acoustic output power from a given driver."

From Wikipedia

Thank you for trying to help me understand this.
Dave D

A good analogy to an acoustical horn is an electrical transformer. You feed the transformer with a high pressure (voltage) and low current and it is transformed to low pressure and high current (large displacement). Both horns and transformers are lossy but pretty efficient.

For all you techno geeks..... Here is the theory for the Exponential horn (Orthophonic) that will give you some background.

https://www.grc.com/acoustics/an-introd ... theory.pdf

Yea, it is overkill, but it is a good read.....

Mark

A simple explanation to people who express an "interest" is: "It just works"... I'm sure they're not looking for techno speak or horn theory.
Your demonstration of removing the connector and then replacing it is enough to show that it works. If anyone wants to go further, suggest pursuing a college degree in the science of sound theory...

Actually, print out the article that Mark (Maginter) posted and give it to them, that should be easy enough for anyone to understand...