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3d Printed acoustic lens, XT25, Thingiverse
3d Printed acoustic lens, XT25, Thingiverse
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Old 8th July 2017, 06:43 PM   #41
Gaga is offline Gaga  Europe
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3d Printed acoustic lens, XT25, Thingiverse
Quote:
Yes please.
OK, I'll do.

Quote:
I posted a "brain-dump" on how to build these things here:
http://www.diyaudio.com/forums/multi...ml#post5126615
In fact your thread was one of my most important sources during evaluation how-to build an 'Acoustic Lens'. Thanks a lot for sharing.

Gaga
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Old 8th July 2017, 06:57 PM   #42
Patrick Bateman is offline Patrick Bateman  United States
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No problem!

The fun part with these lenses is you can do some really bizarre stuff, like mate them to a traditional waveguide. I think you could also feed the lens with dual compression drivers, similar to this JBL setup:

Click the image to open in full size.

See this D2? And see how sound enters from the left and from the right?
Now rotate that 90 degrees and put a SAW lens at the top and at the bottom.
You'd have one waveguide fed by TWO compression drivers. Should be able to raise your on-axis SPL by about 5-6dB. Or lower the cutoff. Pick one.
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Old 16th July 2017, 07:15 PM   #43
Gaga is offline Gaga  Europe
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3d Printed acoustic lens, XT25, Thingiverse
Default Acoustic Lens with 3/4 '' tweeter

Hi 454Casull,

As I did not manage to take new measurements due to very limited time, I add some measurements of the printed acoustic lens using a SB19ST (19mm) tweeter and some information on the construction of the acoustic lens model.

The acoustic lens is based on the information available from the respective patent. See as well the thread by Patrick mentioned above.

3D-constuction:
3d Printed acoustic lens, XT25, Thingiverse-acoustic-lens-v9c-druck-fin-v3-v4-abec-v2-v2-ellypse-2-png

I did quite some ABEC simulation work during construction of several variants:
3d Printed acoustic lens, XT25, Thingiverse-2017-07-15-acoulens-abec-wo-sym-1-jpg

Simulation of SPL at 55cm distance by ABEC:
3d Printed acoustic lens, XT25, Thingiverse-2017-07-15-acoulens-v9c-abec-spl-1m-1-png

Simulation of horizontal directivity by ABEC:
3d Printed acoustic lens, XT25, Thingiverse-2017-07-15-acoulens-v9c-abec-sono-horiz-6-36db-3-png

Situation of horizontal directivity, normalized to 0:
3d Printed acoustic lens, XT25, Thingiverse-2017-05-15-abec-simu-acoulens-sb19-1m-directivity-sono-horiz-norm0-3-27db-4-png

Measurement of horizontal directivity using SB19ST tweeter (19mm dia), mic distance 55cm:
3d Printed acoustic lens, XT25, Thingiverse-2017-05-15-acoulens-sb19-mic55cm-directivity-sono-horiz-1k-16k-2-png

Comparison of horizontal directivity (SB19ST) normalized to 0:
3d Printed acoustic lens, XT25, Thingiverse-2017-05-15-acoulens-sb19-mic55cm-directivity-sono-horiz-1k-16k-norm0-vs-abec-simu-1-png
Measurement (upper half of image)
ABEC simulation (lower half of image)

Please note that the model simulation in ABEC was slightly different from the final printout - thus the observed differences between simulation and measurement. However, ABEC was still extremely helpful to understand some basic principles of how the acoustic lens worked.

I will probably construct an improved version based on the experiences with this model. More information probably in a German hifi-forum then...

Gaga

PS: For details on construction with ABEC see how-to ABEC thread here.
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Old 16th July 2017, 08:29 PM   #44
Patrick Bateman is offline Patrick Bateman  United States
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How are you creating your ABEC mesh?

Are you doing it in a 3D program and then importing it into ABEC?

And if so, which one?
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Old 16th July 2017, 09:10 PM   #45
Gaga is offline Gaga  Europe
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3d Printed acoustic lens, XT25, Thingiverse
I'm importing the *.step file from a 3D-program into Gmsh. Meshing is then done with Gmsh and the mesh imported to ABEC.

See as well description here.

Gaga
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Old 16th July 2017, 09:18 PM   #46
Patrick Bateman is offline Patrick Bateman  United States
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Very cool.

It looks like I could output a STL file from 123D, and import it into Gmsh:

[Gmsh] Imported stl mesh size control

That would allow me to do my designs in 123D, where I'm very fast, and simulate them in ABEC
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Old 16th July 2017, 09:24 PM   #47
Gaga is offline Gaga  Europe
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Yes - just play around with 'options' for the meshing process in Gmsh in order to achieve the best fitting mesh for your puproses - and calcualtion time on your computer (example here).
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Old 17th July 2017, 07:00 AM   #48
freddi is offline freddi  United States
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3d Printed acoustic lens, XT25, Thingiverse
~ OT - are there such things as optimal Karlson front chamber shapes?
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Old 17th July 2017, 01:05 PM   #49
nailhead is offline nailhead  Germany
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Hi Christoph

Very cool simus and mesaurements.

The normalized simus are scaled from +3 to -27dB whereas the measurements are scaled from +0 to -30dB. Did you matched the scales in the comparison graph? For me it seems not, so maybe then it looks even better.

Gre
Andreas
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Old 17th July 2017, 08:53 PM   #50
Gaga is offline Gaga  Europe
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3d Printed acoustic lens, XT25, Thingiverse
Hi freddi,

Quote:
~ OT - are there such things as optimal Karlson front chamber shapes?
Frankly, I do not know. Could be probably simulated using ABEC. Closest things I worked on was the simulation of diffraction slots using Akabak (see here, watch out, German...).

Hi Andreas,

Quote:
Very cool simus and mesaurements.
Thanks a lot!

You are right, I did not correctly align scales of measurements and simulations.

There are more shortcomings with the simulation:
- Have to check distance of simulation vs measurement;
- The printed lens slightly differs from the simulated lens (rounded edges);
- The SB19 was not simulated as a dome, but as a flat disc;
- Have to check the TSP I used to simulate the SB19;

I'll go back to the simulation, check things and re-do the simu...

Gre,
Christoph
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