By the way, if anyone wants to design and 3D print their own phase plus, the phase plug on the Celestion CDX1-1425 is plastic and removable. So a great candidate for tinkering with this.
Celestion CDX1-1425 Neo 1" Compression Horn Driver 25W
I'm not thrilled with the price - at $100 there's quite a few choices that are superior. But a good candidate for phase plug tinkering.
So there's really no need to be too precise even about the velocity vectors?
I understand that the shape of the outline would be similar enough to a spherical cap. But what about the velocity vectors (axial vs radial)? If that doesn't really matter then I don't know what I'm trying for here...
No, I suppose they are not the same. Most of these convexely used drivers are either custom designs or customized existing designs. Eg Fyne Acoustics uses an existing compression driver with a customized "aerated rear chamber".
An interesting quote by djk (R.I.P.) wrt smaller convexely used drivers:
"The horn is quite shallow, so it can't load very low in frequency, but it is active horn loaded in the top octave.
If you want to hear what the horn faceplate actually does, just remove it (the driver is twist-locked onto the faceplate). I think you will be surprised at how much it contributes to the sound.
Avantgarde uses a custom compression driver for the midrange in the Trio, the compression ratio is on the order of 2:1, and it sounds very open compared to typical 10:1 midrange drivers."
An interesting quote by djk (R.I.P.) wrt smaller convexely used drivers:
"The horn is quite shallow, so it can't load very low in frequency, but it is active horn loaded in the top octave.
If you want to hear what the horn faceplate actually does, just remove it (the driver is twist-locked onto the faceplate). I think you will be surprised at how much it contributes to the sound.
Avantgarde uses a custom compression driver for the midrange in the Trio, the compression ratio is on the order of 2:1, and it sounds very open compared to typical 10:1 midrange drivers."
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Perhaps, but many people (including Tom Danley) seem to like the Community drivers (low compression ratio, but as result also bandwidth limited).
kessito also mentions something about the compression ratio in one of his posts today.
The Community drivers are technically oldskool/obsolete and not comparable to modern drivers such as the BMS and Faital. Personally, I wouldn't use those classic drivers, but it might nonetheless be useful to study legacy technology. This of course applies in particular to Western Electric.
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Your target at the throat of the conical horn is a perfect spherical wavefront ("breathing spere" ) with equal velocity at the whole surface
try it in ABEC, make a spherical cap, you have the option to make it "breathing" (believe its called pulsating or something and than a simple conical horn with the angles perfect matching the spere, if you combine this with the perfect temination then you will get the best result.
Of course this "breathing" is not the same as a diaphragm moving forward and back, so this is something that you also do with the channels.
From there on you can decide how much and which compromises you are willing to make in the translation to the less than perfect world.
There are no free lunches, it's all about compromises and choices made, the only advantage that the skilled diyer has is that you can decide to spend a relatively huge amount of money on custom cnc'd phaseplugs and use low WAF huge waveguides to achieve excellent results.
Will it be commercially viable? no, definately not.
Will it sound good? hell yeah
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resin 3d printer might be a good candidate to produce phase plugs:
What Does Resolution Mean in 3D Printing? | Formlabs
the M200 is outperformed by modern BMS drivers, particularly the dual diaphragm midrange. However in comparison to contemporary drivers and most non dedicated midrange drivers its harmonic distortion/output is exceptional. It has no phase plug in order to limit its high frequency extension and reduce distortion.
What Does Resolution Mean in 3D Printing? | Formlabs
the M200 is outperformed by modern BMS drivers, particularly the dual diaphragm midrange. However in comparison to contemporary drivers and most non dedicated midrange drivers its harmonic distortion/output is exceptional. It has no phase plug in order to limit its high frequency extension and reduce distortion.
kesito probably referred to the combination of phase plug and waveguide, in order to achieve excellent results with the (horn + driver) system.