2 Attachment(s)
CNC copy of an 2328 adapter
I have started drafting a 2328 from an actual unit I have in hand. I understand there might be inconsistencies between units and that castings can vary widely. This is a work-in-progress and I am trying to understand the progression rate from throat to mouth.
Attachment 51857
Pics of the Balloon, please
Quote:
Originally Posted by
Lee in Montreal
That "balloon" irregularity is what puzzles me. I want to transfer the drawing into Solidworks and measure the area progression.
Can You post a few detailed pics of the balloon?
Ruediger
Guessing the mind of an unknown engineer
Quote:
Originally Posted by
Lee in Montreal
Here it goes. The horizontal progression is smooth and makes sense. The vertical progression shows the Ø 2" machining ending into a cavity (with a bad step). I believe that this "balloon" is only the result of the mass production at reduced costs where minimal machining must be involved. Considering the wide tolerances in many units, precision and accuracy were probably not the first target.
Attachment 51864
Maybe the designer had an idea similar to the following one.
Perhaps You have seen the weird folds in the Klipschorn, where the horn gets wider in the vertical direction, and narrower in the horizontal direction. It opens more rapidly in the vertical direction than it should, and as a compensation gets narrower in the horizontal direction.
The 2328 gets wider more rapidly than it should, and it gets narrower from the middle of the balloon towards the slot.
Let's check the dimensions. Upper frequency bound is 10 kHz (2440 driver), with a wavelength of 3.4 cm. The dimensions of the 2328 (magnitude-wise) are roughly 3.4 cm.
Upper frequency bound of the Klipschorn is 400 Hz, but let's calculate with 340 Hz, which is about the same (magnitude-wise). @ 340 Hz the wavelength is 1 meter, which is roughly the dimension of the Klipschorn.
So at the slot it's a "Klipsch-style" horn expansion. If a Klipschorn makes sense, then this adapter must do as well.
At the round entry to the adapter You can't do much to transform or guide wavefronts. Any expansion is wrong. The sudden change from the entrance to the balloon is a discontinuity which does no harm. But the balloon itself paves the way for the "Klipsch-style" expansion.
Weird idea? May be :)
Ruediger
no need for common cutoff frequency
You can join segments of any flare (exponential, hyperbolical, conical) and of any cutoff frequency. The segment with the worst properties determines the behaviour of the combination. If that segment is short compared to the wavelengths involved, then it's a simple discontinuity.
If You wanted to achieve plane waves so that You could more easily design an acoustical lens, then You would pick a very low cutoff frequency.
Ruediger
Never said it that way either.
Hey Ruediger,
OK, but "may" could go for any horn, good or bad. Still in my opinion the best horns for HiFi today are with the same flare all the way. About the biradials I donīt know as I havenīt examined them, but they sound OK. Would be nice if you showed their design.
Did some Googling and found they are CD horns. Keele did the EV HR series and after that, at JBL in order to get around some patents, designed the Biradials. Looks nicer to me as they are smoother without the edge(?) when going from exp to conical. Read that paper long ago so I donīt remember the explanation.
Canīt find the word "guessing" in my answer to you;). I mention "guesses" after my answer to you, about a subject that wasnīt directed to you mainly.
I used it after having seen 1" adapters here with designs that must have been based on guesses.