An easy to build classic horn?

dabbler

Disabled Account
2010-04-15 3:13 pm
Between cities!
This is just for fun really. I have a pile of foamcore sheets at home and was thinking of making some large horns with easy to build profiles, like the altec mantaray horn.

If I dont like it I can toss it, no harm done. Any other easy horn designs out there that would be worth a try? Up to 500mm (20 inches) wide and deep would be ok and 600-700 hz crossover would be nice.
 

dabbler

Disabled Account
2010-04-15 3:13 pm
Between cities!
Without the flares and templates you can forget about building the horn. But if you decide how you want it, Fs, At(driver-area), type(Tx, Exp, etc) , number of petals(from four), I will make it for you. Go for a square Tractrix!

Thanks for the help, I had a look through the HR help manual and it makes sense now, so I should be able to get something happening on my own! I will eventually build a tractrix and le cleach but I will start with a square conical, simply because it is easy to build with stiff foamcor.

It seems that cutoff frequency cannot be entered for a conical horn (F12). Why is that? I can enter it for tractix and le cleach without a problem....?
 

dabbler

Disabled Account
2010-04-15 3:13 pm
Between cities!
Yes i've noticed that the conical gets very big in order to get sufficient for a low cutoff, like an OSWG. See the SPL plot attached for a 30cm long horn (50 degrees) which shows drop off at 800hz then a bump 400 before it drops off steeply. Could we say that the cutoff is at 800? If so should I double the frequency to 1600hz for the crossover point as is done with tractrix and le cleach horns?

Tractrix does have good "bang for buck" in terms of size vs cut-off. Will be interesting to compare the sound to my OS waveguide.
 

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It seems that cutoff frequency cannot be entered for a conical horn (F12). Why is that?

Hi dabbler,

A conical horn does not have a specific theoretical cutoff frequency. To illustrate:

Attachment 1 shows the normalised throat acoustical impedance of an 'infinite' exponential horn having a cutoff frequency of 100 hertz. Notice how the resistance (black trace) falls abruptly to zero at 100 hertz.

Attachment 2 shows the normalised throat acoustical impedance of an equivalent 'infinite' conical horn. In this case there is no sharp reduction (or cutoff) in resistance at a particular frequency.

Kind regards,

David
 

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I am trying to export a tractrix horn design as a rectangular tractix flare however from the dropdown list I can only see the Conical, Exponential and Uni flares?

Hi dabbler,

The Con, Exp and Uni options relate to how the width of the rectangular horn is flared. The rectangular cross-sectional area itself still expands as required for a tractrix horn.

Uni is probably the option to choose, unless perhaps you wish to use Con to achieve some degree of constant directivity in the horizontal plane.

Kind regards,

David