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Did Siegfried Linkwitz miss a trick?
Did Siegfried Linkwitz miss a trick?
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Old 17th November 2020, 10:31 AM   #261
Mattes is offline Mattes  Germany
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Hi Don,


I believe these large bits are intended for stationary routers. A 38mm bit on a hand router, well... be careful. The biggest router I found would not allow this without base plate (aluminium) modifications, so I decided to stop at 25mm. And Im always happy when this part is finished and prefer routing with my smaller, better Festool router.


Generally, I would think that a large chamfer is a nice alternative and may even be used as a design element, as Scott suggests.


Somewhere Ive read that a rule of the thumb for roundover radius is 1/10th of the baffle width or more to be effective. But surely, the more the better applies here, and with the largest roundover possible youll end up with a sphere, or nearby. This will have its own effects on the drivers response.


From another perspective, I find it interesting to care about transition from the drivers cone to the baffle. In the flowers, Ive tried to maintain the most even, undisturbed flare or path from the cones central area to the baffle edges, and I think that this is important. For that reason, I described the flowers, even with their funky look, as a form-follows-function design. The only design element without function is the polishing of the counterweight and the AEs phase plug...


All the best


Mattes
Attached Images
File Type: jpg DSC05041 2.jpg (722.3 KB, 170 views)
File Type: jpg DSC04300klein.jpg (411.8 KB, 168 views)
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Disclaimer: Im the international distributor for FERTIN ACOUSTICS fullrange drivers and am thus biased by commercial interest. Please have a look at https://guentherengineering.com for further information.
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Old 26th November 2020, 08:04 PM   #262
scottjoplin is offline scottjoplin  Wales
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Interesting baffle shape here, more a wheel than a tyre Ultimate Open Baffle Gallery
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Old 29th November 2020, 08:38 PM   #263
kaameelis is offline kaameelis  Estonia
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I simulated this "wheel" OB on Akabak 3 with 6 1/2" speaker and find torus like "tyre" seems better, specially in polar plot. Also this type OB drives Akabak to the limits. If I change meshing type (bifurcation vs. delaunay) or meshing size, even if mesh frequency is much higher than simulated range, I get very different results.
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Old 29th November 2020, 09:16 PM   #264
scottjoplin is offline scottjoplin  Wales
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Can you post the sims?

BTW, he's crossing over just above the dipole peak so the baffle shape shouldn't mess things up much.
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Old 30th November 2020, 12:09 PM   #265
kaameelis is offline kaameelis  Estonia
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Later can post. Wheel probably had different diffraction and also cavity resonance, also space between magnet and wheel is significantly smaller than on torus.
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Old 30th November 2020, 04:58 PM   #266
kaameelis is offline kaameelis  Estonia
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Some results. Wheel is: OD 260 mm, ID 172 mm, speaker 6 1/2.
Polar plot is with 2 different speaker cone meshing versions. First Bifurcation, second Delaunay meshing. Simulations are one others copy in all other details. SPL curve is compensated with +15dB low shelf filter, to get usable mid response. Results are very different. I prefer Delaunay, but its level is obviously not correct, speaker has sensitivity 87 dB 2.83Vrms/1m. Simulation is also made on 2.83Vrms and for 1 m measurement distance.
I added also on axis response comparison, C1 is Bifurcation front 1m, C2 rear 1 m, C3 is Delaunay front, C4 rear.
Attached Images
File Type: png PolarBifurcation.PNG (162.6 KB, 47 views)
File Type: png PolarDelaunay.PNG (163.0 KB, 45 views)
File Type: png Wheel1.PNG (229.3 KB, 46 views)
File Type: png Wheel2.PNG (219.2 KB, 18 views)
File Type: png Compensation1.PNG (30.2 KB, 18 views)
File Type: png OnAxis1m.PNG (58.4 KB, 15 views)

Last edited by kaameelis; 30th November 2020 at 05:22 PM.
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