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-   -   How much stock should I put in these simulations (http://www.diyaudio.com/forums/full-range/229882-how-much-stock-should-i-put-these-simulations.html)

Bas Horneman 12th February 2013 02:27 PM

How much stock should I put in these simulations
 
2 Attachment(s)
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.

Bas Horneman 13th February 2013 07:42 AM

Bump.


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Scottmoose 13th February 2013 09:42 AM

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.

Bas Horneman 13th February 2013 10:46 AM

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.

wintermute 13th February 2013 11:11 AM

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.

Bas Horneman 13th February 2013 11:32 AM

1 Attachment(s)
Hi Tony,

The sim with golden ratio height. But centered.

Regards,
Bas

xrk971 13th February 2013 11:50 AM

Bas,
Where do you get this software?
Thanks,
X

Bas Horneman 13th February 2013 11:54 AM

Hi X,

Loudspeaker Design Software

Scroll all the way down.

Regards,
Bas

GM 13th February 2013 02:18 PM

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

Bas Horneman 14th February 2013 03:14 PM

Quote:

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


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