Horn Loudspeakers?

[ellisdj]

Reason I was surprised is because I thought a horn design was a tool for extending bass response from a driver - a way of getting more out of it, and expected the big drivers used in older speakers to naturally have better extension because they are bigger coupled with the horn.

I assumed then in a 2 way design it would have to used differently to cover the mids.

Goes to show I little I know about these speakers - its interesting thanks

 

[Vladimir]

Good engineering involves compromises too. Even-order harmonic distortion under 80Hz is really no big deal.

 

[DocG]

These Arcardian Audio Pnoes are said to go down to 40 Hz no problem. Fancy a pair?

 

[davedotco]

Reason I was surprised is because I thought a horn design was a tool for extending bass response from a driver - a way of getting more out of it, and expected the big drivers used in older speakers to naturally have better extension because they are bigger coupled with the horn.

I assumed then in a 2 way design it would have to used differently to cover the mids.

Goes to show I little I know about these speakers - its interesting thanks

A horn for a loudspeaker is best thought of as an impedance matching device, a kind of acoustic transformer.

It's job is to 'transform' the vibrations (energy) in a relatively hard, inelastic material material, the speaker cone, into a much 'softer' elastic material, air. I have forgotten much of what I once knew about this subject but it effectively transfers more of the energy in the cone into the air, hence increasing the efficiency of the transducer as a whole.

Within the passband of the horn, the effective, in enclosure, sensitivity of the driver is increased. This technology was developed for the motion picture industry where the primary chalange was to get room filling spls from the relatively low powered valve amplification of the day. Bandwidth, particularly at the bass end was not that important, even giants such as these had modest bass extension but above the cutoff frequency of the front horn (around 100hz), the sensitivity of the system would be in excess of 100dB/watt/metre.

This is a simple two way system with controlled dispersion from the multicell horn which covered everything above 500hz. To give you an idea of scale, those are 15inch drive units.

 

[Vladimir]

If anyone has heard an oldy gram with a huge horn and voice box playing. Those things get insanely loud, yet if you remove the horn the sound comes down to nothing.

 

[davedotco]

If anyone has heard an oldy gram with a huge horn and voice box playing. Those things get insanely loud, yet if you remove the horn the sound comes down to nothing.

This whole impedance matching thing has a huge effect, I should know how to calculate this but I have long forgotten, it was routine stuff back in the day.

In the cash strapped uk of the 50s, Hartsfields and Klipschorns were unheard of so a budget design was required for the hard up enthusiast of the day. The Paraline was a simple enclosure using an 8inch 'twin cone' drive unit by Wharfedale or Goodmans, it was very much a diy project. At it's simplest, it was something like this...