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Old 18th September 2020, 10:29 PM   #71
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by xrk971 View Post
It just so happens that I have a 3D model of the K15. It has been scaled by 0.44x but someone should be able to apply global scaling to get it back to 1.0x full size. Here is the STL file. The render of the wireframe looks like this:


This one has skinny little slot vents that I think will suffer compression losses and add distortion, but the basic shape is there:


Go knock yourselves out with Akabak3 or ABEC3!

I have a model of it in Akabak 1 that works pretty well for freq below 500hz:

A Speaker that Kicks Butt in Large Spaces
Someone requested that the 3D model be provided in STEP file format.
Attached Files
File Type: zip K15-0.44x-Speaker-v01-STEP.zip (21.7 KB, 4 views)
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Old 24th September 2020, 08:45 AM   #72
kipman725 is offline kipman725  United Kingdom
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I had a go at this K15 simulation but my results are not making much sense, just getting a response like a resonant pipe. Any ideas? (simulation files attached).
Attached Images
File Type: png response.png (126.3 KB, 152 views)
File Type: png fields.png (266.5 KB, 93 views)
Attached Files
File Type: zip K15.zip (954.4 KB, 3 views)
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Old 24th September 2020, 09:36 AM   #73
xrk971 is offline xrk971  United States
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This was a 0.44x scaled 3D model, did you upscale it by2.27x to get back to 1.0x scale? Even at 0.44x scale the response should be different. I don't use Akabak3 so cannot check your files. What driver did you use?

Here is what I get with my model for an EV SP15A driver at 2.93m and 1m:
AKABAK 3-k15v3e-evsp15a-freq-2-83v-1m-png

Here is predicted impedance:
AKABAK 3-k15v3e-evsp15a-imped-png

Predicted cone excursion for 2.83v:
AKABAK 3-k15v3e-evsp15a-displ-png

From the impedance and displacement curves, we can see that the box tuning of the K15 with the EV S15A driver is about 45Hz.

T/S params:
Code:
Def_Driver  'EV SP15A' | 103 dB Qts 0.45, 5.1 mm xmax
  SD=855cm2   |Piston
  fs=40Hz
  Qms=5.0
  Qes=0.49 
  Re=6.2ohm 
  Vas=280L
What does your predicted impedance look like, that is usually a good indicator if your model is working well.
Attached Images
File Type: png K15V3e-EVSP15A-Freq-2.83v-1m.png (29.2 KB, 178 views)
File Type: png K15V3e-EVSP15A-Imped.png (9.5 KB, 175 views)
File Type: png K15V3e-EVSP15A-Displ.png (11.0 KB, 169 views)
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Last edited by xrk971; 24th September 2020 at 09:58 AM.
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Old 26th September 2020, 05:43 PM   #74
kaameelis is offline kaameelis  Estonia
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Quote:
Originally Posted by kipman725 View Post
I had a go at this K15 simulation but my results are not making much sense, just getting a response like a resonant pipe. Any ideas? (simulation files attached).
I tested file. I find Interfaces normals where in wrong direction. After change I get next result.
I understand scaling to original size is made already in mesh file.
I get warning when opening file that it was made with newer version of AKABAK and some feature may be lost. I had 3.1.2 b59 AKABAK, as I understand latest available. With what version was the K15_attempt2 made? After opening frequency range was 10-2kHz, not as you original 10-500Hz. I also notices that in Observation was missing Fileds1 and Polar1
Attached Images
File Type: png K15Capture.PNG (77.7 KB, 15 views)

Last edited by kaameelis; 26th September 2020 at 05:57 PM.
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Old 27th September 2020, 07:08 AM   #75
freddi is offline freddi  United States
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FWIW, for a reference vs simulations

here's an outdoor measurement, with mic laying on the ground and 2M away from a Karlson K15 loaded with the now defunct - small motor Eminence Beta15CX speaker. https://www.parts-express.com/pedocs...ions-44613.pdf

Click the image to open in full size.
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Old 28th September 2020, 02:02 AM   #76
freddi is offline freddi  United States
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K15 nominally tunes in the 45Hz region. Deletion of the front "shelf" and its associated port boundary may move that up a couple of Hz. What T-S parameters were used for the simulation?

I think the front shelf board did some correction of the first dip. Making the front chamber a few inches less deep would probably make better graph and allow deletion of that front deflecting board.

I'm interested in the 0.44 scale version as could make a fun sub -sat system which could play quite loud.
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Old 28th September 2020, 11:51 AM   #77
kipman725 is offline kipman725  United Kingdom
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Thanks for your efforts efforts kaameelis and xrk971. I did work out that the normals where the wrong way round on the interfaces and got a peaky result like kaameelis did, so I didn't post as it still looked wrong. The mesh is scaled back to normal K15 size and the driver T/S are the Emminance Kappa Pro 15A. I'm not super familer with Karlson designs, what is the front shelf?
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Old 28th September 2020, 11:50 PM   #78
freddi is offline freddi  United States
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the front part of the shelf was gapped about 9cm from the inside of the aperture. XRK971's model IIRC deletes that part. Karlson did not use it in any of the smaller models. It may have been used in Karlson's 18 inch console and was used by Cetec-Gauss in their 5181 K18 cabinet.
Attached Images
File Type: png K15 side view.png (90.6 KB, 20 views)
File Type: jpg Factiry K18 1280.jpg (753.5 KB, 19 views)
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Old 29th September 2020, 08:30 PM   #79
kaameelis is offline kaameelis  Estonia
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I find one parameter wrong in K15_attempt2 simulation file, VC inductance was 100 times bigger than is for Kappa Pro 15A.
Result seems better now, relatively close to measured.
Attached Images
File Type: png K15Corrected2.PNG (40.4 KB, 31 views)
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Old 30th September 2020, 05:55 AM   #80
freddi is offline freddi  United States
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hi kaameelis - That is pretty impressive !. I wonder if the 0.44 scale version looks similar only moved up in frequency and also what happens with the horizontal polars for the 0.44X case.
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