AudioCircle
Industry Circles => GR Research => Topic started by: atoluma on 26 Jul 2017, 06:18 pm
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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 diffraction 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:
(http://www.audiocircle.com/image.php?id=166001)
It's far more effective than I though, nearly perfect response (green curve after modification, red before modification)
(http://www.audiocircle.com/image.php?id=166002)
I will give up the waveguide! :green:
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That looks really good.
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wow - nice work. Post this over at diyaudio - they'll love it.
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ok, I will ;-)
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I'll give this a try with our new tweeters that are arriving shortly.
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Very interesting! :)
I'm about to build something with Neo3 and Neo8 and will definitely try this out. Do you mind sharing? Either the 3d file or the measurements? And maybe a Neo8 version too? :)
If not, then no worries. I will try drawing it myself - it looks simple enough, though I have little experience.
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The measurement are on the post already! :green:
For the shape it's a cylinder cut in half, very easy to make with sketchup.
You can apply it to every BG planar: same construction; same diffraction, same benefit!
The only thing I don't know is if the space between the magnet is the same on the neo 8
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Measurements yes .. I meant dimensions, sorry :)
I've made one in Tinkercad already but don't know the exact dimensions as I don't have the drivers here with me.
Neo3 has a thickness of 11mm vs. 8mm on the Neo8, so maybe it won't make that big a difference on the Neo8, but I think I'll try anyway when the time comes.
Do your little tweak have any effect on the horizontal dispersion?
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4,6mm x 54,5mm
For the horizontal dispersion I will made measure soon!
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Excellent!
Two questions:
1. How do you attach the strips?
2. Might the strips alleviate the frequency rise in the Neo-8 making the notch filter unnecessary?
Thanks.
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Bonding!
I didn't test the NEO 8 but diffraction doesn't explain everything!
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Cool , nicely done 8)
jay
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I'm wondering if this stuff might work: M-D Building Products 1025 All-Climate Auto and Marine 17-Feet Weather Seal Strip, Black. It already has an adhesive backing, and it is cheap!
(http://www.audiocircle.com/image.php?id=166051)
Just cut down the centerline for width, and cut to length.
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The density is a little low compared the solid resin. Odds are it would measure better than stock, the question is how much better.
Scotty
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The measurement are on the post already! :green:
For the shape it's a cylinder cut in half, very easy to make with sketchup.
You can apply it to every BG planar: same construction; same diffraction, same benefit!
The only thing I don't know is if the space between the magnet is the same on the neo 8
I was wondering if this would work on the Neo 8, and if so would it be as beneficial. (That would take an awful lot of work on the LS6/9)
Interesting. Good job!
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atoluma, was that measurement done with the tweeter mounted in a waveguide and the strips on the back ?
jay
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hi! no just the BG mounting plate.
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I have never tried 3D printing, I'm more of a 3D CNC removal guy : )
To simplify mounting and automate alignment print the whole shebang in one shot.
Add small connecting crossbars with temporary cut off tabs that align to the neo3 mounting cutouts.
Makes sense, only if you have a big stack of neo's to do.
Shawn
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hi! no just the BG mounting plate.
So what am I missing ? How come both (before mod & after) are playing down so low if no Wg ? A NEO 3 PDR starts rolling off around 1.8k
Might be stating the obvious but remember too, if you are planning on using the tweeter fully open (no back), with conventional drivers, you'll need to physically align the tweeter with the voice coils of the woofer(s) for front/rear time alignment
jay
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Or electrically align it with time delay.
The diffraction pieces on the Neo3 look very interesting. Looking forward to the horizontal response plot.
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Or electrically align it with time delay.
The diffraction pieces on the Neo3 look very interesting. Looking forward to the horizontal response plot.
hey Rich ,
in an open config withthe tweeter firing front / rear, if the tweeter isn't aligned physically with the woofer voice coil you could align one side but you'd misaligning the other side by the same amount
jay
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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 diffraction 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:
(http://www.audiocircle.com/image.php?id=166001)
It's far more effective than I though, nearly perfect response (green curve after modification, red before modification)
(http://www.audiocircle.com/image.php?id=166002)
I will give up the waveguide! :green:
Reviving this old post
Has this been discussed more in other posts?
Is there anyone on the forum that can print out a set for me?
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I've done some testing on my own, a couple years ago, and the difference is very small. I even tried different heights to see if i could get a better response, but there wasn't much difference. Smoother in a couple places, but not nearly as drastic as the above results.
The measurements in that graph are most likely near-field measurements, where the round-overs will likely have a larger effect.
In my testing standard testing at 1 meter any differences were quite small, with most changes being +/-2dB happening between 5-5KHz.
When I tested then again in Danny's rig, the differences were even smaller.
The best layout was a tall one in the middle with two round rods.
I probably still have some rods floating around that I can test for more accurate measurements and save the measurements. To share here. Just depends on how long it takes me to find/print more rods our of PLA instead of flexible resin.