How much stock should I put in these simulations - diyAudio
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Old 12th February 2013, 03:27 PM   #1
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Default How much stock should I put in these simulations

I used Diffraction & Boundary Simulator 1.20.

First off I calculated the golden ratio position in my open baffle and did a sim.
Then I used the NoBox plan. i.e. 90cm from floor and center of the baffle.
The result of the simulations is attached.

Driver is Visaton B200.

I noticed that there was a dip around 1kHz with the "nobox" placement and a bump before. The Golden Ratio graph looks less ragged.
Attached Images
File Type: png NOBOX.png (41.4 KB, 117 views)
File Type: png GOLDEN RATIO.png (40.6 KB, 109 views)

Last edited by Bas Horneman; 12th February 2013 at 03:46 PM.
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Old 13th February 2013, 08:42 AM   #2
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Bump.


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Old 13th February 2013, 10:42 AM   #3
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Short answer: it depends. Technically an offset is usually preferable (although golden ratio is a bit of a myth in some ways). However, you have to factor room response into these things, which usually screw things up below ~300Hz, and the polar response of the drive unit. The B200 has a rapidly narrowing power response as frequency increases, & while this has it's obvious drawbacks, it does tend to render it a little less vulnerable to some (some) baffle effects.
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Old 13th February 2013, 11:46 AM   #4
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Thanks Scottmoose. I'm aware of the offset usually being preferable. I have an old Phillps document where they suggest that. The golden ratio was just a starting point. But seems at least from a simulation aspect to have one of the flattest responses.

Anyway thanks for your reply.
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Old 13th February 2013, 12:11 PM   #5
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Hi Bas, did you try the driver centered at the same height as the golden ratio one? I've found with BDS that the vertical position on the baffle can make a big difference.

I read once somewhere (I think it was duntechs site but I checked there and didn't see it) that the particular designer had moved away from asymetric baffle placement due to negative effects (I think from memory on imaging). I ended up going with centre placement after reading that.... I wish I had the reference...

Tony.
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Old 13th February 2013, 12:32 PM   #6
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Hi Tony,

The sim with golden ratio height. But centered.

Regards,
Bas
Attached Images
File Type: png gr_center.png (40.1 KB, 80 views)
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Old 13th February 2013, 12:50 PM   #7
xrk971 is offline xrk971  United States
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Bas,
Where do you get this software?
Thanks,
X
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Old 13th February 2013, 12:54 PM   #8
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Hi X,

Loudspeaker Design Software

Scroll all the way down.

Regards,
Bas
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Old 13th February 2013, 03:18 PM   #9
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Using your baffle as a monopole measured at the old 4 ft standard distance and setting the room boundaries to '0' to mimic a corner, calculating x = 15.41", y = 27.4" looks close enough for me; ditto as a dipole 4" from rear wall and measured 45 deg off axis horizontally.

With the rest of the boundaries missing though, not to mention another speaker, furniture, etc., it's accuracy will rapidly degrade except over a narrow BW.

Still, a useful tool, especially for near-field apps.

GM
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Old 14th February 2013, 04:14 PM   #10
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Quote:
Still, a useful tool, especially for near-field apps.
Thanks.
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