Acoustic Horn Design – The Easy Way (Ath4)

Thank you, this is really valuable. What I noticed now, what was not obvious before, are the little spikes at roughly 1.7 - 2.7 - 3.9 kHz. These seem to be common to both cases, which suggests it's actually the waveguide (or something else, common to both). They should disappear even from the spectrograms if EQed out, though. In fact, I can imagine this could be ringing of the horn. Maybe this could be confirmed somehow.

Regarding distortion, larger diaphragms should always have an edge towards the lower frequencies. That's to be expected.
 
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With a passive crossover, this can still be tricky. Anyway, it should be possible to do much better than this.
Certainly a lot easier going to active route:

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And there is no reason not to use both, some passive parts to manipulate impedance and affect distortion performance, and independently optimize frequency response (and even phase) with DSP. I find it really archaic to limit oneself to some certain technology as everything seems to have pros and cons it's then logical to mix and match to get top performance.
 
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The only case that seem to exist is high impedance drive of "poor" mid/hf... but with high quality drivers the need for passive components as a distortion suppressor is not really needed - or? But this have been beaten to death in other threads so...

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Does anyone know what mesh frequency to use?

I've been using 1000Hz for years, and noticed that many of you are using a much higher frequency. In increased things to 20khz, and the sim never finished. I've backed it down to 16khz and so far, it's taken nearly 24 hours for the sim to reach 67%

I have an eighteen core CPU and 64GB of ram and it's still taking over a day to finish a sim...

There's a 3+ year old post with some guidelines here: https://www.diyaudio.com/community/...-design-the-easy-way-ath4.338806/post-6234490

That post is a bit confusing to me, as it recommends a mesh frequency of 1khz, but I see people using frequencies that are 20khz and even higher?
 
It depends on a model used. With a full 3D mesh you're typically limited to several thousand elements in ABEC to work smoothly (I always try not to exceed 5000). But this is best controlled by the mesh resolution parameters in the Ath scripts, not mesh frequency (which is kept low, e.g. 1 kHz, so that ABEC doesn't subdivide the mesh further itself). In CircSym mode (axial symmetry) however, the usable limit for mesh frequency is much higher - several tens of kHz are no problem. And even this is possible to "overwrite" by a large number of segments in the script (always the best approach), so the mesh frequency itself has no actual relevance.
 
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Finally got around to getting my own models & whatnot running in the new AKABAK. I've been really curious what the predicted impact of having a hole in the waveguide for MEH style horns actually is. Generated the profile in Ath4 so I could compare the my solidworks -> gmsh -> akabak workflow and make sure I wasn't messing anything up. Results dont look pretty to me (unsurprisingly) and I think it really solidifies how much better an approach like what genelec is taking could be. Maybe some interesting information for some.
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I don't see those results as bad. It's a wiggle of a couple of decibels.
And you can probably clean it up with some clever positioning and hole shape.
 
I don't know 🙂 Somehow I still don't quite like the idea of making holes to waveguides, but there are two very different questions related: Is it the best what we can do? I still have my doubts. But is it good enough to bring a lot of pleasure listening music? Absolutely, I have no doubts about it, if you like it, go for it.
 
I agree, it might be maskable etc, and maybe with careful hole placement, it could be minimised. but its only going to 'smear' the result.

to me, it probably makes more sense to try integrating the driver into the waveguide, a-la genelec or this martin speaker, this one is full range. but if you limit the low end like the genelec, you should be able to the the excursion below 1mm, allowing you to have a smooth interface with the horn. I'll put up some tests with that in soon. but using the axial mode, it seems you can displace the surfaces by that much and not do too much to the response at all.
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