BG NEO 3 FR optimization

atoluma · « **on:** 26 Jul 2017, 06:18 pm »

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:

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

I will give up the waveguide!

Danny Richie · « **Reply #1 on:** 26 Jul 2017, 07:00 pm »

That looks really good.

Angaria · « **Reply #2 on:** 26 Jul 2017, 09:09 pm »

wow - nice work. Post this over at diyaudio - they'll love it.

atoluma · « **Reply #3 on:** 26 Jul 2017, 09:15 pm »

ok, I will

Danny Richie · « **Reply #4 on:** 26 Jul 2017, 11:00 pm »

I'll give this a try with our new tweeters that are arriving shortly.

Fjendbo · « **Reply #5 on:** 27 Jul 2017, 07:01 am »

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.

atoluma · « **Reply #6 on:** 27 Jul 2017, 07:08 am »

The measurement are on the post already!

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

Fjendbo · « **Reply #7 on:** 27 Jul 2017, 07:58 am »

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?

atoluma · « **Reply #8 on:** 27 Jul 2017, 09:40 am »

4,6mm x 54,5mm

For the horizontal dispersion I will made measure soon!

THROWBACK · « **Reply #9 on:** 27 Jul 2017, 12:42 pm »

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.

atoluma · « **Reply #10 on:** 27 Jul 2017, 01:29 pm »

Bonding!

I didn't test the NEO 8 but diffraction doesn't explain everything!

Captainhemo · « **Reply #11 on:** 27 Jul 2017, 04:17 pm »

Cool , nicely done

jay

THROWBACK · « **Reply #12 on:** 27 Jul 2017, 09:11 pm »

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!

Just cut down the centerline for width, and cut to length.

*Scotty* · « **Reply #13 on:** 27 Jul 2017, 10:42 pm »

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

SoCalWJS · « **Reply #14 on:** 28 Jul 2017, 12:05 am »

Quote from: atoluma on 27 Jul 2017, 07:08 am

The measurement are on the post already!

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!

Captainhemo · « **Reply #15 on:** 28 Jul 2017, 12:56 am »

atoluma, was that measurement done with the tweeter mounted in a waveguide and the strips on the back ?

jay

atoluma · « **Reply #16 on:** 28 Jul 2017, 06:06 am »

hi! no just the BG mounting plate.

MarvinTheMartian · « **Reply #17 on:** 28 Jul 2017, 01:23 pm »

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

Captainhemo · « **Reply #18 on:** 28 Jul 2017, 03:35 pm »

Quote from: atoluma on 28 Jul 2017, 06:06 am

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

HAL · « **Reply #19 on:** 28 Jul 2017, 03:43 pm »

Or electrically align it with time delay.

The diffraction pieces on the Neo3 look very interesting. Looking forward to the horizontal response plot.