It's probably similar to the phenomenon with Dr. Geddes's axisymmetric OS waveguides (it was an on-axis dip IIRC), which is avoided with SEOS waveguides.
In an OS waveguide the on axis dip or generally rough 0 axis response occurs when the DI is held to be ruler flat, if the OS is modified to allow the directivity to rise even a little bit that goes away.
A good way to check is to normalize to 10 degrees off axis instead of 0 and see if the response still looks the same or quite different.
The diffraction is still there with non-axisymmetrical, it's just more diffuse on the frequency spectrum which can be a misleading indicator. Earl didn't see it as the issue that was often put to him, as long as the waveguide is otherwise well designed.
It looks like a diy - Revel M105!Getting closer now...
The revel doesn't suppress the SB15 upper frequency resonance, so any active version of this speaker that takes it into account will have a leg up in that regard. Any preliminary passive crossover schematics, or all active?
I did prototyping actively, so that is pretty much finalized. I will make variants for active since it is so easy to do and people can see if they like a variant better. I'm also going to do a variant that uses a passive notch for the woofer breakup to tame the harmonic distortion that active notches can't do. Once all that is finalized I'll do a passive version.
I'm not sure if this qualifies as ruler flat, but the on-axis hole can be eliminated to a high degree even with such a flat-DI device -
In fact, there's no such thing as an "OS" waveguide, as it would need to be infinite... Once you have to terminate it, it becomes something else.
Explained well in this app note from Purifi: https://purifi-audio.com/blog/app-notes-2/low-distortion-filter-for-ptt6-5x04-naa-11
Did anyone have experience or information about that printer: https://www.3djake.at/elegoo/neptune-4-max
Pretty cheap for that size and at least on paper looks better equiped as my CR10 V3.
Would be a good exchange for my printer and when I need more prints and better quality in the future I can add one of these modern closed volume fast print ones.
Pretty cheap for that size and at least on paper looks better equiped as my CR10 V3.
Would be a good exchange for my printer and when I need more prints and better quality in the future I can add one of these modern closed volume fast print ones.
No it is not, and your example demonstrates just how little it has to rise. Earl's own waveguide and the one bmc0 made force the DI flat in the OS section and as a consequence have more 0 axis trouble.
Actually, even the term "constant directivity" isn't quite accurate.
It rather should be "linear directivity".
With a pure constant directivity the off-axis lines would be all spaced evenly as well as being entirely flat, not on a (constant) slope.
This could basically only being created with a full cardioid system.
And even than getting it all evenly spaced is quite the challenge.
Changing this spacing is yet ever more difficult (going from fully omnidirectional to a extreme cardioid)
I designed 3 baffles using SB26 waveguide and 3D printed them.
The first is a 5-inch waveguide.
The second is a 5-inch waveguide with a chamfer.
And the third is a 6-inch waveguide.
I will measure the directivity of the three baffles to determine the baffle shape of my DIY speaker.
I am deeply grateful to Augerpro for providing an opensource waveguide to enable this design.
The first is a 5-inch waveguide.
The second is a 5-inch waveguide with a chamfer.
And the third is a 6-inch waveguide.
I will measure the directivity of the three baffles to determine the baffle shape of my DIY speaker.
I am deeply grateful to Augerpro for providing an opensource waveguide to enable this design.
And how much filling? How much material did you need?
I just got my Elegoo Neptune 4 MAX yesterday. Maybe not the finest prints but it's so much faster as my old printer ...
I just got my Elegoo Neptune 4 MAX yesterday. Maybe not the finest prints but it's so much faster as my old printer ...
I will upload the measurements after I build the turntable. Measurements will probably be possible in mid-November.
These were printed using a Prusa MK4. The size of the baffle is 160mm x 250mm x 25mm.
The material is PLA, the filling is 15%, and the layer thickness is 0.1 mm. I'm not sure exactly how much material was used.
Can you probably weight one of the parts? Does it need 0,1mm layer resolution? Do you have the feeling 15% infill is enough?
I'm just about to start similar trials - so I'm curious. Get my bigger printer 2 days ago and doing some testprints at the moment. I have some problems with the model staying on the surface cause movements are so fast, it get's loose. But should be ok with a huge, flat panel.
I'm just about to start similar trials - so I'm curious. Get my bigger printer 2 days ago and doing some testprints at the moment. I have some problems with the model staying on the surface cause movements are so fast, it get's loose. But should be ok with a huge, flat panel.
For acoustics purposes I have found that 0.1mm layers are overkill. 0.2mm is completely fine, even for tweeter waveguides. The biggest benefit of 0.1mm layer height is purely visual ime. When printing waveguide prototypes I have used 20-25% infill, and this has worked just fine. For peace of mind the completed waveguides have been printed at 100% infill, which is more demanding in terms of material, but also in terms of thermal control during printing (warping occurs much more easily with 100% infill).
For a front baffle I think the idea of printing/moulding a baffle that goes on top of a "normal" MDF or plywood baffle (like Dutch&Dutch) is a good idea if you're gonna stick to rectangular shapes anyway, in those cases I don't see the benefit of 3D-printing the entire baffle. If you're making complex shapes (Genelec, Vivid audio) 3D-printing the whole thing makes more sense.
For a front baffle I think the idea of printing/moulding a baffle that goes on top of a "normal" MDF or plywood baffle (like Dutch&Dutch) is a good idea if you're gonna stick to rectangular shapes anyway, in those cases I don't see the benefit of 3D-printing the entire baffle. If you're making complex shapes (Genelec, Vivid audio) 3D-printing the whole thing makes more sense.
Baffles weigh about 180g. 0.1mm layer thickness is not essential. These baffles will be used for directivity comparison tests, not for actual speakers, so 15% is enough. I think a higher filling is needed for actual speakers.
I agree. I plan to print the waveguide to be mounted on the actual speaker with SLA. It's purely for good looks.
I agree with this too. These three baffles are for testing purposes only. The baffles in my actual speakers will be aluminum.
Hello,
I would be interested to know how you go about directivity matching of the waveguide and midrange. What do you consider there?
I once read that the waveguide should be about the same size as the midrange driver and that the baffle width also plays a role, or is that rather negligible for a waveguide?
Are there other things to consider centre-to-centre spacing, edge radius of the cabinet, etc?
I would be interested to know how you go about directivity matching of the waveguide and midrange. What do you consider there?
I once read that the waveguide should be about the same size as the midrange driver and that the baffle width also plays a role, or is that rather negligible for a waveguide?
Are there other things to consider centre-to-centre spacing, edge radius of the cabinet, etc?