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-   -   Acoustic Horn Design – The Easy Way (Ath4) (https://www.diyaudio.com/forums/multi-way/338806-acoustic-horn-design-easy-ath4.html)

TNT 20th September 2021 04:32 PM

Just speculating if the ridge of delayed energy between 2 and 5k could be those 2 tips vibrating like a tuning fork...

//

sheeple 20th September 2021 06:04 PM

Probably edge diffraction ;)

tmuikku 20th September 2021 07:58 PM

1 Attachment(s)
Diffraction looks like that, dip on-axis and off-axis ridge. Anyway, no mouth roundover seems to do this. Here is RCF H100 showing similar response. Asked a friend to print the petal version of 260, not here yet :)

Noviceman 20th September 2021 08:55 PM

Love to see this kind of fiddly works, even if I'm not willing to design or make one :)

sheeple 21st September 2021 01:01 AM

Quote:

Originally Posted by tmuikku (https://www.diyaudio.com/forums/multi-way/338806-acoustic-horn-design-easy-ath4-post6791794.html#post6791794)
Diffraction looks like that, dip on-axis and off-axis ridge. Anyway, no mouth roundover seems to do this. Here is RCF H100 showing similar response. Asked a friend to print the petal version of 260, not here yet :)

Idk, if the waveguide shows considerable waistbanding between 1.3k and 2.7k, maybe. But what I see is ups and downs in the HF, the cause being lower, presumably already at 1.3k (26 cm wavelength). The diffraction causes more energy on-axis over 1.3k and this is why normalized looks as if the wg is waistbanding. From 5k on you can clearly see the pattern rip through the frequency band. Let’s see what it will do baffled. Yes, free standing does not have this problem, sure.

Mazza 21st September 2021 01:49 AM

Quote:

From 5k on you can clearly see the pattern rip through the frequency band.
G'day sheeple, would you be good enough to explain what you mean be this and how to read this from the graphs please?

Cheers.

mabat 21st September 2021 04:44 AM

There will be all kinds of problems if the device is not properly terminated, which of course it isn't in this case (besides the fact it has a hole in it). Placing it in a box should improve the things a long way and I'm only curious how much, compared to the free standing version, as an actual comparison hasn't been done so far. It will be interesting to see.

sheeple 21st September 2021 12:19 PM

1 Attachment(s)
Quote:

Originally Posted by Mazza (https://www.diyaudio.com/forums/multi-way/338806-acoustic-horn-design-easy-ath4-post6792104.html#post6792104)
... and how to read this from the graphs please?

I see this:
Attachment 985041

26 cm diameter equals 1.3 kHz, this is where diffraction occurs naturally (edge of the waveguide). First dip is not too obvious because of the energy overhang of the waveguide there. But then follows the usual bump, stronger on-axis, when 0-axis is normalized it looks like waistbanding, and the pattern continues.

Marcel simulated the free standing ST260 baffled-device performance: Diffraction
You will see the behaviour. Also compare to infinite baffle: No diffreaction
Your data kind of aligns to this, doesn't it.

Mazza 21st September 2021 12:50 PM

Thank you very much for that clear and informative explanation sheeple. Much appreciated. I learnt something new just now - its a good day when I learn something new!

I was very impressed with the measured performance of the ST260/B so I'm definitely going to get it into an enclosure - at some point - so many wave guides, too little time (esp as a single father of 3).

sheeple 21st September 2021 02:56 PM

You are welcome, bet the kids love the waveguides ;) Consider reasonable round over for the final cabinet. A cheap 1-1/2 inch (about 4 cm) radius router bit can be bought from Yonico, or use chamfered edges of comparable dimension. I am very interested to see the baffled response.


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