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What would be your horn curve if horn loading isn`t your goal?

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Posted on July 24, 2014 at 11:00:56
mdg
Audiophile

Posts: 51
Location: Gilze-Rijen (Holland)
Joined: November 27, 2004
 Hi,


What should be the ideal curve of the horns if I want to achieve maximum flat directivity and not care about sensitivity of the system:

- if the exit of the compression driver would produce flat planar waves
(so not taken into account the interference that the drivers itself
could produce)
- assuming a frequency range, let`s say from 100hz to 20khz.

Greetings,
Marcel



 

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RE: What would be your horn curve if horn loading isn`t your goal?, posted on July 24, 2014 at 12:38:55
weltersys
Industry Professional

Posts: 685
Location: FL
Joined: September 28, 2004
 Conical, but a conical expansion would have to be very narrow and huge to provide directivity control to 100 Hz.

 

RE: What would be your horn curve if horn loading isn`t your goal?, posted on July 25, 2014 at 08:17:56
Inmate51
 Coming back to reality...

There are no, none, zero, nada, drivers which will "nicely" go from 100 Hz to 20 KHz.

And, a 100 Hz horn will be VERY large.

So, the "curve" question is moot.

I will have to disagree with Weltersys about conical. They have issues. Read Harry Olson's work on horn flares in "Acoustical Engineering" and in "Music, Physics and Engineering".

:)

 

RE: What would be your horn curve if horn loading isn`t your goal?, posted on July 26, 2014 at 17:37:01
tomservo
Manufacturer

Posts: 8193
Joined: July 4, 2002
 Hi
Art is correct, straight sided or mostly straight sided horns are the easiest way to get constant directivity over a wide band when efficiency isn’t a concern. The reason can be seen by examining Don Keele’s pattern loss formula which infers the point within the horn that sets the pattern angle, moves up the horn as the frequency climbs. That is why traditional curved wall horns exhibited a narrowing pattern with increasing frequency.

http://www.romythecat.com/pdf/Keele%20%281975-05%20AES%20Preprint%29%20-%20Whats%20So%20Sacred%20Exp%20Horns.pdf

http://www.fohonline.com/current-issue/73-speaking-of-speakers/7463-understanding-horns-part-2.html

Also shown in the references is that the conical horns have inferior loading at the lower end of their response. The reason is that the horn’s impedance transformation has a “high pass” factor included in it and an examination of the conical horn shows that at the apex, the expansion rate is very rapid and so provides poor loading at the bottom end but if one tapes into the flare downstream where the expansion rate is slower, then one can horn load to a lower frequency.
While the thumb rule for an ideal horn is that the mouth should be about 1 wavelength in circumference, one can get some horn gain at a much smaller size. For example, a 28 inch square mouth and 50 degree horn, provides some horn gain (gain over the same driver as a direct radiator) at just above 100Hz.
The requirements for high frequency and low frequency operation are to a very real degree contradictory so it is not possible to make a truly wide band horn with only one driver and even the driver dimensions will govern how high one can “fill out” the horn angle. For example, a one inch exit planar wavefront driver can only fill out a horn up to about 50/60 degrees at 20K.
Best,
Tom Danley

 

RE: What would be your horn curve if horn loading isn`t your goal?, posted on July 26, 2014 at 20:59:33
Inmate51
 "conical horns have inferior loading at the lower end of their response."

Yes, we get that.

And, they have issues with distortion components.

:)

 

RE: What would be your horn curve if horn loading isn`t your goal?, posted on July 27, 2014 at 08:54:14
tomservo
Manufacturer

Posts: 8193
Joined: July 4, 2002
 "And, they have issues with distortion components."

Yes for a given acoustic power, they have much less throat distortion than the types that offer more loading.

 

RE: What would be your horn curve if horn loading isn`t your goal?, posted on August 11, 2014 at 11:53:56
mdg
Audiophile

Posts: 51
Location: Gilze-Rijen (Holland)
Joined: November 27, 2004
 Hello,

Thanks for the detailed information.



Gr.
Marcel

 

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