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Dispersion diffraction directivity horn


mopardave

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I think the easiest way to explain the differences in horns/waveguides is to offer the write-up on the Peavey Quadratic Throat Waveguide (QTW), which discusses the various types of horns and their strengths/weaknesses:

 

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.536.5361&rep=rep1&type=pdf

 

The K-402 and K-510 horns are different than the ones mentioned in this article, but you can think of them as "conical" (actually straight-sided) horns with mouth flares that are tractrix in their geometry, i.e., they roll out to flush to the mouth mounting flange in the horizontal axis and almost roll out to flush in the vertical axis. 

 

Chris

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I'm not aware of anyone using the term "dispersion" horn.  Acoustic horns typically have some sort of dispersion angles such as wide or narrow. And some like the K-400 have vertical dispersion which varies aka collapsing polars. PWK called this controlled directivity.

 

Diffraction horns were used long ago and have a mouth with an extreme aspect ratio, about 1:8 I'd say.   At right angles to the narrow side the sound diffracts into a wide angle.  It looks to me that the K-1000 seen in very early Heresy and Shorthorns are like this.  Edit: EV had one too.

 

If you look at the article which Chris recommends, you'll see that the dispersion horn lives on in horns like the Manta Ray and others.  About midway down the horn there is a slot.  Therefore it is actually a diffraction horn mated to a more pyramidal horn.  Sound is diffracted at the slot into a wide angle to paint the final portion.

 

The fourth reference in the article is D.B. Don Keele's article What's So Sacred . . . ."  You can Google it.  Excellent.

 

 

WMcD

 

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Ok, thanks guys.   I found a couple reads that said the diffraction horn disperses better horizontally when mounted vertically.   I remember some posting of others here back when I built these that also agree'd with this theory. That was one reason I built them with the vertical horn.    My thought now is why cant I do the same with the Cornscala build using a diffraction horn vertically.  I believe it would be a first vertical Cornscala.   I would use the Crites diffraction horn vertical and possibly a 2 way as well.    The way I built the vertical Cornwalls I don't think I can get the motor board out to use the Crites motor board.   Might look weird, but its just another option for me.   I will post the link if I can find it.

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2 hours ago, glens said:

Didn't it say the wider dispersion up high was across the narrow inner (throat) slot?  If so you'd want that part vertical even when the mouth is wider than tall that way.

That's how I understand it. The notch needs to be in a vertical position to get wide horizontal dispersion.  It's mostly mumbo jumbo to me.  Directive horns work fine for me as I sit in one spot in front of the speakers while listening.

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I believe the amount of dispersion is widest at low frequencies where the slot is most narrow in terms of wavelength.  

 

The early Cornwalls were made to be turned so the mid is vertical or horizontal though I think the reason was mostly aesthetics and performance might have been at best different rather than better.

 

If you can't decide whether horizontal or vertical is better for you, you could mount the horn diagonally like one model of Shorthorn.  Then consider 45 degrees or 135 degrees.  Mirror image stereo pairs?  Smile.

 

 

Shorthorn Diagonal .jpg

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1 hour ago, WMcD said:

I believe the amount of dispersion is widest at low frequencies where the slot is most narrow in terms of wavelength.  

 

The early Cornwalls were made to be turned so the mid is vertical or horizontal though I think the reason was mostly aesthetics and performance might have been at best different rather than better.

 

If you can't decide whether horizontal or vertical is better for you, you could mount the horn diagonally like one model of Shorthorn.  Then consider 45 degrees or 135 degrees.  Mirror image stereo pairs?  Smile.

 

 

Shorthorn Diagonal .jpg

LOL!  Yeah just slit the difference.  I will get some measures tomorrow. Maybe I can mount the mid horn horizontal and keep the tweet vertical right where it's at. Second though......diagonal wouldn't look too bad.

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Just measured the CW's. Looks like the Crites mid horn m2380 will have to be mounted horizontal and the tweet vertical leaving enough room to still look normal.  So that is the plan.

On 3/7/2019 at 11:40 AM, WMcD said:

I believe the amount of dispersion is widest at low frequencies where the slot is most narrow in terms of wavelength.  

 

The early Cornwalls were made to be turned so the mid is vertical or horizontal though I think the reason was mostly aesthetics and performance might have been at best different rather than better.

 

If you can't decide whether horizontal or vertical is better for you, you could mount the horn diagonally like one model of Shorthorn.  Then consider 45 degrees or 135 degrees.  Mirror image stereo pairs?  Smile.

 

 

Shorthorn Diagonal .jpg

Hahaha! That's funny.  Yeah just slit the difference.  Gonna get some measures tomorrow .  Maybe if the mid horn is big enough I can mount it hori

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