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Multi-Way Conventional loudspeakers with crossovers

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Old 23rd January 2021, 04:44 AM   #5101
mabat is offline mabat  Czech Republic
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BTW, to view a pressure field, simply add this to the "observation.txt" file:

Code:
Nodes "FieldNodes"
  Scale=1m
  1  -0.2 0.3
  2  0.4 0.3
  
Field "F1"
  RefNodes="FieldNodes"
  EdgeLength=10mm
  BodeType=LeveldB; StepSize=3
  Range=60
  1 1 2
You will probably want to reduce the number of frequencies however, otherwise it will take quite a long time.

To see the throat in detail you can easily increase the resolution and limit the field area:

Code:
Nodes "FieldNodes"
  Scale=1m
  1  0.0 0.2
  2  0.15 0.2
  
Field "F1"
  RefNodes="FieldNodes"
  EdgeLength=3mm
  BodeType=LeveldB; StepSize=3
  Range=60
  1 1 2
Attached Images
File Type: png field-1.PNG (78.8 KB, 404 views)
File Type: png field-inside.PNG (21.3 KB, 392 views)
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Last edited by mabat; 23rd January 2021 at 04:46 AM.
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Old 23rd January 2021, 04:59 AM   #5102
mabat is offline mabat  Czech Republic
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I just realized there are several options for the field type (BodeType):
"LeveldB, Ampl, Real, Imag, Phase, LeveldB_Phase, Ampl_Phase, Complex"

I've never experimented with this. Maybe it could show something interesting.
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Last edited by mabat; 23rd January 2021 at 05:14 AM.
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Old 23rd January 2021, 12:41 PM   #5103
Arnandsway is offline Arnandsway  Netherlands
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Quote:
Originally Posted by mabat View Post
As some start to print and measure the ST260, maybe it's useful to collect (again) the results so far - this is a courtesy of Pet007 who measured virtually the same WG before (maybe there was a tiny difference, I don't really remember), with three different drivers -

Just a note - the DI as shown is calculated from the front polars only (the only measured). The "real" DI will be closer to the simulations, where it is full-space.
What crossover frequency would one want to use with this WG? My guess would be around 1200 hz to keep a smooth DI?
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Old 23rd January 2021, 12:59 PM   #5104
mabat is offline mabat  Czech Republic
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Quote:
What crossover frequency would one want to use with this WG?
This depends mainly on the compression driver used - what it can handle. Generally you want the lowest XO frequency possible with what you have. Then you simply choose a woofer size that makes a smooth overall DI. If we assume that most of the 1" drivers can handle 900 - 1000 Hz with ease, what should be the right woofer size for this, looking at the DI around this frequency (around 7 dB)? I don't know off the top of my head - maybe 12", maybe 10"... There is some freedom anyway.
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Last edited by mabat; 23rd January 2021 at 01:09 PM.
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Old 23rd January 2021, 04:36 PM   #5105
JSS is offline JSS  Canada
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Quote:
Originally Posted by mabat View Post
Now it would be great to have this measued to see if it's real to that extent. If it was, the whole system would "ring", i.e. there would be strong peak(s) in the frequency response and accompanying ringing in the time domain. Correctable with EQ but somewhat troublesome. What's interesting is that it has virtually no effect on radiation pattern.
I'll print and measure to see if it's a real problem and report back. It's printing now hopefully it doesn't crap out. It's 9hrs to print half. Hoping to have something to report soon...
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File Type: jpg 2021-01-23_12-32-09.jpg (157.4 KB, 345 views)
File Type: jpg 2021-01-23_12-27-55.jpg (148.3 KB, 344 views)
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Old 23rd January 2021, 05:17 PM   #5106
Arnandsway is offline Arnandsway  Netherlands
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This is what I get from a simulation in Vituixcad. I simulated the diffraction-response from two 8" woofers on a 25x90 cm baffle. I SPl-traced the measurements of the ST260 + B&C DE502. And then I did some EQ'ing to get the responses flat.
Crossover is at 1000 hz LR4, this gave the smoothest DI. Note that the SPL-traced tweeter response only goes to 90 degrees, while the diffraction simulation goes 360 degrees.

Here is the dashboard from Vituixcad and below that the diffraction-tool.


Click the image to open in full size.
Click the image to open in full size.
Attached Images
File Type: jpg Vituixcad dashboard.jpg (708.0 KB, 83 views)
File Type: jpg diffraction tool.jpg (159.1 KB, 92 views)

Last edited by Arnandsway; 23rd January 2021 at 05:20 PM.
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Old 23rd January 2021, 09:29 PM   #5107
jzagaja is offline jzagaja  Poland
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Anyone tested low resonance hard rubber material (Shore D 65) vs high resonance standard PLA/ABS or with fibers 25mm thick with low infill? I mean SPL difference at 100dB if any or subjective observations? Augerpro?
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Old 24th January 2021, 06:36 AM   #5108
mabat is offline mabat  Czech Republic
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Quote:
Originally Posted by JSS View Post
It's printing now hopefully it doesn't crap out. It's 9hrs to print half. Hoping to have something to report soon...
I'm holding my breath...
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Old 24th January 2021, 05:17 PM   #5109
JSS is offline JSS  Canada
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Ok you can breathe now The print split in the middle of the round over. So I'm thinking of making it thicker there and print with higher temp. See how it goes...

I'm new to 3d printing, if you guys have suggestions, please feel free.
It's been frustrating but fun at the same time lol
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File Type: jpg IMG_20210124_085330.jpg (251.5 KB, 102 views)
File Type: jpg 2021-01-24_13-03-47.jpg (99.1 KB, 97 views)
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Old 24th January 2021, 05:26 PM   #5110
mabat is offline mabat  Czech Republic
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Aww, I feel your pain. I'm not an expert either.
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