Acoustic Horn Design – The Easy Way (Ath4)

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#5,921
when trying to model a midrange waveguide for example an 6,5 inch midrange cone driver how you would start configuring the config file?
Normally this driver then runs between the 200-3000Hz range.
In this frequency range the (especiall at 200-1000Hz) driver naturally has a wide dispertion pattern. So does this make sence to adjust the "Throat.Angle" to mach the directivity in the lower starting range? So for example set this to about 50 degrees which will maybe match the 200-1000Hz range (-6db; in both directions)? How you would start the config file (indpenenent form coverage angel or which contour to use) modelling a midrange with ath4?
 
#5,924
mabat said:
This is what I get for an axisymmetric shape. The throat impedance is indeed increased below 1 kHz by the means of the resonance. Is this a good idea? Maybe, I don't know.
Now the question is whether and how much can an elliptical shape improve this. Maybe it can.
Click to expand...

If you extend with moderation, the overshoot is not as crazy 🙂
HF beaming is my plague...
Is there a way to expand HF spread without using diffraction and still provide a decent load? 😕😕😕
 
#5,926
The horn throat is a circle, however by making the throat shape change from a circle to an ellipse has made it possible to widen the horizontal dispersion, while keeping the coverage angle small and thus loading the CD better.

It's about making the transition from circle to ellipse as close to the throat as possible.
 
#5,928
aragorus said:
The horn throat is a circle, however by making the throat shape change from a circle to an ellipse has made it possible to widen the horizontal dispersion, while keeping the coverage angle small and thus loading the CD better.

It's about making the transition from circle to ellipse as close to the throat as possible.
Click to expand...

i.e. it's a diffraction slit, which will widen the coverage, but create a large resonance in that tube. Hence the result. Not what I would want. Bring the cone out round and then vary the coverage angle and I'll bet you get your "better loading" without so much resonance.
 
#5,929
aragorus said:
HF beaming is my plague...
Is there a way to expand HF spread without using diffraction and still provide a decent load? 😕😕😕
Click to expand...

No, unfortunately not, but luckily there's the principle of "soft (or smooth) diffraction". In fact, an OS throat is an example.
I've been researching this for quite some time now and it seems we're looking for the same "compromise".

Personally, I don't mind increased beaming > 8-10 kHz and I suppose you don't either
 
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#5,930
Ro808 said:
No, unfortunately not, but luckily there's the principle of "soft (or smooth) diffraction". In fact, an OS throat is an example.
I've been researching this for quite some time now and it seems we're looking for the same "compromise".

Personally, I don't mind increased beaming > 8-10 kHz and I suppose you don't either
Click to expand...

gedlee said:
i.e. it's a diffraction slit, which will widen the coverage, but create a large resonance in that tube. Hence the result. Not what I would want. Bring the cone out round and then vary the coverage angle and I'll bet you get your "better loading" without so much resonance.
Click to expand...

I agree completely!
And in fact a diffraction slot is what I would like to avoid.
Here are the front and side contrours of the horn. The narrowing of the throat is very subtle.

I don't claim to have found the holy grail of horns, it's just my attempt to tackle the problem.

red_front.JPGred_side.JPG
 
#5,931
What's the main difference between a traditional diffraction slot, or, as Dr. Geddes just noted: slit, and a smooth/soft diffraction slot?

A traditional diff. slot features a constriction > there is only expansion in one plane - the vertical in most cases, and a narrowing in the other.
As a result, the wavefront suddenly widens as soon as it reaches the end of the slot, with all the dire consequences.

A soft slot omits the narrowing.
 
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#5,934
mabat said:
This is what I get for an axisymmetric shape. The throat impedance is indeed increased below 1 kHz by the means of the resonance. Is this a good idea? Maybe, I don't know.
Now the question is whether and how much can an elliptical shape improve this. Maybe it can.
Click to expand...

mabat said:
Right now there is this waveguide being made (422 x 364 mm; 1,4" throat for 18Sound ND3T) -

Could it be made for a 2" driver?

Also, would you recommend this type of waveguides for coaxial compression driver? I have a pair of B&C DCX50-8's and those have a ring mid-tweeter around a small tweeter (which has its own min-trumpet). I guess the ring mid-tweeter generated a spherical wave so it would go well with a waveguide, and the small tweeter (10K+) would be very directional and therefore beam tightly without reflections on the waveguide's walls. So I see what could make this a good choice - however, I do not foresee what could go wrong...
Click to expand...
 
#5,938
aragorus said:
And in fact a diffraction slot is what I would like to avoid.
Here are the front and side contrours of the horn. The narrowing of the throat is very subtle.

I don't claim to have found the holy grail of horns, it's just my attempt to tackle the problem.

View attachment 924366View attachment 924367
Click to expand...
Obviously, I didn't comprehend the actual inner shape. This is quite different than what I showed. I've tried all different kinds of these "higher loading" variants, it always beamed more than I would like.
 
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