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BG NEO 3 FR optimization
BG NEO 3 FR optimization
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Old 26th July 2017, 09:21 PM   #1
atoluma is offline atoluma  France
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Lightbulb BG NEO 3 FR optimization

I always found that NEO 3 pdr is a nearly perfect tweeter excepted the frequency response.
When I studied the construction, I found that this tweeter sufering of difraction because of the magnets in front of the diaphragm.

So I've design some flexible resin shape to bond on the tweeter surface (on both side).

This shape cancel the diffraction effect of the tweeter housing

It's 3D printing with formlabs flexible resin:
BG NEO 3 FR optimization-plan1-jpg

It's far more effective than I though, nearly perfect response (green curve after modification, red before modification)

BG NEO 3 FR optimization-plan2-jpg

I will give up the waveguide! :green:
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File Type: jpg plan1.jpg (150.2 KB, 432 views)
File Type: jpg plan2.jpg (299.4 KB, 425 views)
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Old 27th July 2017, 12:08 PM   #2
lowmass is offline lowmass  United States
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wow

I wonder if any further improvement if those bars were "bullet" shaped ?

I wouldnt be suprised if your mod with a small rounded wave guide would smooth the sharp roll off at the top end a bit. However what you got looks so effective you are likely at the point of diminished return

Last edited by lowmass; 27th July 2017 at 12:12 PM.
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Old 27th July 2017, 01:01 PM   #3
ashok is offline ashok
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BG NEO 3 FR optimization
Wow, this looks great. I cant have it printed. Might have to think of an alternative !
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Old 27th July 2017, 01:33 PM   #4
Gerrit Boers is offline Gerrit Boers  Netherlands
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Excellent result!
Did you measure the off-axis response? Given this result it makes sense to do a set of measurements for a directivity plot. I would also be interested in the cumulative spectral decay. To round it off you could measure the harmonic distortion, just to be sure that there isn't a trade off somewhere.

regards,

Gerrit
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Old 27th July 2017, 03:10 PM   #5
lowmass is offline lowmass  United States
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Ive been doing a ton of testing recently on slot shapes for tru ribbons. I see very similar FR shaping results as altoluma is getting here and have only seen improvments on off axis as well with no big changes in waterfall and distortion.

Basically sharp changes in geometry make wiggles. Nothing new there but that respose altoluma is getting from simple half round bars is as mentioned better than expected. Gota love that.

I suspect if you flush mount that neo3 so that tops of half rounds are flush with baffle it would be even better.
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Old 27th July 2017, 03:22 PM   #6
Davey is offline Davey  United States
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I've seen some (and I've made some myself) Neo3PDR measurements and they look much better than your red curve.

Here's one example from John Krutke a few years ago. Very flat through the 3-5khz range where your measurement shows a huge 13db variation.
Zaph|Audio

There's something else going on here.

Dave.
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Old 27th July 2017, 03:45 PM   #7
atoluma is offline atoluma  France
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This is the curve with the back cup in place . You can see it by the 1,5kz cut off.
The back cup give a better FR

here the two curve (within/without) from the neo3 datasheet:
BG NEO 3 FR optimization-neo-jpg
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File Type: jpg neo.jpg (213.2 KB, 173 views)

Last edited by atoluma; 27th July 2017 at 03:56 PM.
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Old 27th July 2017, 04:09 PM   #8
Davey is offline Davey  United States
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I'm not talking about back cup issues. I'm well aware of those.

The back cup was in place for both of your modification before/after measurements above, yes???
I think as Gerritt mentioned, you need to make some off-axis measurements as well.

Dave.
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Old 27th July 2017, 04:54 PM   #9
lowmass is offline lowmass  United States
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Hmm good points

altoluma, from your measurments it looks as if the back cup was removed?

also could you describe the baffle the Neo 3 was mounted to in your measurements?

Last edited by lowmass; 27th July 2017 at 05:03 PM.
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Old 27th July 2017, 05:00 PM   #10
atoluma is offline atoluma  France
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Quote:
Originally Posted by Davey View Post
The back cup was in place for both of your modification before/after measurements above, yes???
no back up, free air!
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