Home » Audio » Speaker » Horn gain - directed sound or acoustic transformer?
Horn gain - directed sound or acoustic transformer? [message #16985] Thu, 16 September 2004 15:49 Go to next message
Groove Tube is currently offline  Groove Tube
Messages: 4
Registered: May 2009
Esquire
I was told that horn gain is caused by directed sound focused to a small spot. That is what I always thought about horns. Just the other day I heard it called an acoustic transformer. Is there more going on than aiming the sound? Is it two ways of saying the same thing?

Both! [message #16986 is a reply to message #16985] Thu, 16 September 2004 16:45 Go to previous messageGo to next message
Magnus is currently offline  Magnus
Messages: 32
Registered: May 2009
Baron
The magic with horns is that they are not merely focusing the sound like a parabola antenna compared to an omnidirectional antenna, but actually acoustically matches the driver to the air making it more efficient (acoustic transformer). These are two very different mechanisms.

If you want an electrical analogy, again think of an antenna. Some gain comes from narrowing the dispersion pattern ("antenna gain") some comes from more closely matching the acoustic impedances (lowering back-reflected power i.e increasing SWR for an antenna).

/Magnus

Re: Both! [message #16988 is a reply to message #16986] Fri, 17 September 2004 13:31 Go to previous messageGo to next message
Bill Fitzmaurice is currently offline  Bill Fitzmaurice
Messages: 335
Registered: May 2009
Grand Master
True, but don't put too much emphasis on the directional aspect of horns as a gain source. The primary reason for the apparant gain of a horn with respect to the directional pattern has to do with the physical size of the horn mouth, and the fact that once it hits a wavelength across the radiating pattern shifts to hemispherical, rather than omni-dirctional, and that gets you 6dB of increased on-axis sensitivity. However, you can accomplish the same thing with a direct radiator if you simply make the baffle a wavelength across. The effect of the baffle step as a tool for gain is obvious with horns since they tend to have large mouths compared to the baffles of direct radiators operating in the same frequency range. If you make the respective radiating planes of a horn and a direct radiator the same size, eliminating the horn's advantage as far as the baffle step is concerned, the horn still can easily exhibit 10dB or more of gain over the direct radiator using the same driver.

Re: Both! [message #16989 is a reply to message #16988] Fri, 17 September 2004 18:17 Go to previous messageGo to next message
Oberon is currently offline  Oberon
Messages: 20
Registered: May 2009
Chancellor
"the horn still can easily exhibit 10dB or more of gain over the direct radiator using the same driver."

A direct radiator in 1/8th space exhibits 9dB gain over the same radiator in open space so the directional aspect is significant.

Just an observation. This is not to say the impedance matching aspect is not also significant for its own reasons.

Re: Both! [message #16990 is a reply to message #16989] Sat, 18 September 2004 08:31 Go to previous messageGo to next message
Bill Fitzmaurice is currently offline  Bill Fitzmaurice
Messages: 335
Registered: May 2009
Grand Master
'A direct radiator in 1/8th space exhibits 9dB gain over the same radiator in open space'

So does a horn.

Re: Both! [message #16991 is a reply to message #16990] Sat, 18 September 2004 13:02 Go to previous messageGo to next message
Oberon is currently offline  Oberon
Messages: 20
Registered: May 2009
Chancellor
The output of a 60x60 horn does not increase when radiating in 1/8th space because its pattern is already smaller than that. Only sound sources with a pattern wider than the radiation angle will see a DI increase when the radiation angle is made smaller.

Re: Both! [message #16992 is a reply to message #16991] Sat, 18 September 2004 17:40 Go to previous message
Bill Fitzmaurice is currently offline  Bill Fitzmaurice
Messages: 335
Registered: May 2009
Grand Master
I've never bothered to measure a mid horn corner loaded, but much of what's happening with a LF horn is that corner loading increases the effective path length and mouth area. However, if both the path length and mouth area are already at a full wavelength additional extension isn't going to make any difference, so the increase in SPL is frequency limited; the average bass horn won't see corner loading having much effect, if any, above 200 Hz or so. Your average mid or HF horn is going to have both the path length and mouth cross-section at least a wavelength through most of the passband, so additional length or mouth area will have little or no effect. Yes, the directivity aspect of both wall and corner loading is there, but here again that's only part of the equation, the rest being an improvement of the horn function itself.

Previous Topic: Tapered pipes to horns
Next Topic: Re: Decware Single Driver Fostex F206 Transmission line
Goto Forum:
  


Current Time: Sun Nov 24 17:53:22 CST 2024

Sponsoring Organizations

DIY Audio Projects
DIY Audio Projects
OddWatt Audio
OddWatt Audio
Pi Speakers
Pi Speakers
Prosound Shootout
Prosound Shootout
Miller Audio
Miller Audio
Tubes For Amps
TubesForAmps.com

Lone Star Audiofest