Basic horn question

[Ebag4]

I have a newby horn question.  When a horn is listed as a 80x60 pattern ( elliptical in this case) and the horn has a second flare rate closer to the mouth, what section is 80x60 referring too?  Or is this not really related to the physical horn but the radiation pattern of the sound wave?

 

Thanks,

Ed

[glens]

In my book that would be the nominal coverage pattern (the result).

 

A better question, or at least further, is where in the spectrum range does this pattern pertain, and over how much of the spectrum?  Certainly it will be greater at the bottom and less at the top unless it's a very limited range.

[Chris A]

15 hours ago, Ebag4 said:

...Or is this not really related to the physical horn but the radiation pattern of the sound wave?

This.

 

Horns can be straight-sided (usually referred to as "conical" even though most of them do not follow a conical area expansion equation), or curved such as all other traditional horn profiles such as hyperbolic, exponential, hypex, etc.).  Horns with secondary mouth flares are usually straight-sided near the throat and have secondary flares that can be straight or curving--as in the tractrix mouth expansion used in Klipsch-designed horns. 

 

In the case of the straight-sided varieties, it's usually the portion of the horn closest to the throat that determines the coverage angles--horizontal and vertical if the horn is rectangular or elliptical in mouth shape.  If you can see the throat port while looking inward from the mouth of the horn, just at the point where the throat port starts to become obscured by the internal walls of the horn--that off-angle that you're looking down is usually half the coverage angle of the horn in that horizontal or vertical direction from the central horn axis.

 

Horns don't have set coverage angles vs. frequency, but it is desirable that the angle doesn't change with frequency, i.e., the following polar sonograms are from the K-510 horn using a K-69-A compression driver (horizontal, vertical):

 

 

 

Chris

[Edgar]

9 minutes ago, Chris A said:

Horns don't have set coverage angles vs. frequency, but it is desirable that the angle doesn't change with frequency ...

 

To add further complication, a horn's radiation pattern can also change with distance from the horn. I once measured a microwave horn (wavelength comparable to audio wavelengths) where the radiation pattern in the near field was entirely different than in the far field. Also, the amplitude response varied with 1/distance in the near field and 1/distance² in the far field.

 

Where does the near field end and the far field begin? Where the response changes as described above. Most horns don't have such a pronounced change with distance, so near field and far field may not exist for them.

[Ebag4]

I really appreciate the detailed responses.  You answered my basic question well enough to know I didn’t know what to ask, haha.  I will digest this information.

 

Thanks again,

Ed

Edited January 16, 2020 by Ebag4