2402/2405 Diaphr

[Rudy Kleimann]

That just might work for me! Certainly worth a try now.

Thanks for responding, Toddalin and Grumpy.

Did you run any baseline benchmarks with D8R075 dias? In the same driver?

How does bringing them in at 7KHz take care of a dip above this?

What the "rubber band trick"? Where/how? Got any pics? Any charted results?

I like your shim much better than masking tape.

I like the "Marketing Spin": "Elastomeric" That'll sell...

[toddalin]

That just might work for me! Certainly worth a try now.

Thanks for responding, Toddalin and Grumpy.

Did you run any baseline benchmarks with D8R075 dias? In the same driver?

How does bringing them in at 7KHz take care of a dip above this?

What the "rubber band trick"? Where/how? Got any pics? Any charted results?

I like your shim much better than masking tape.

I like the "Marketing Spin": "Elastomeric" That'll sell...

The magnet was recharged and OCS installed a brand new 2405 diaphram so the tweet was basically as new.

Yes we did both baseline and with the elastomeric filter in place, and I believe that Grumpy may have the data.

They could be crossed a little lower, but I note above 7K because this is typically about the minimum used with the 2405 diaphram that has less mass (because of less surface area) than the 2402. The Jubal crosses over at 6,500 Hz. Regardless, that dip you see between 7-10K is worse on the 2402 than what you see here.

The elastomeric filters are obtained in the produce deparment of the grocery market and are typically found holding bunches of asparagus or broccolli. Most are purple in color.



This is about where it will end up.


It must be applied in real time with simultaneous monitoring. Playing pink noise and watching an RTA, the band is simply slid over the "nose cone" and pushed toward the gap using a toothpick/thin stick. Watching the RTA, just before the gap is closed, the UHF will extend and flatten out. If you go too far, hook the band with a bent pin and pull it back out for another try.

The cost is volume, but using this method, you can actually even get the 2402 diaphram to extend and smooth its response above 10KHz almost to that of the 2405.

[Rudy Kleimann]

and measuring with my calipers. I'll post all my findings when I'm done.


Does anybody know the difference in pole piece height between the 2404H and the -1 variant?

IIRC, Zilch posted pics (and dimensional measurements?) of two different phase plugs from 2404's. I'll PM Zilch about this... it would take me forever to manually review all his threads to find this...

I have here on hand for measuring dimensions:

1-AlNiCo 075 with the "ring clamp" mounting plate from early/mid '70's
1-AlNiCo 2402 with the "new style" mounting flange from early/mid '70's
1-2404H-1? (rear label missing) from a JBL4612B * I can almost make out 2404H1 in very small (much smaller than I've seen on other 2404's) white ink print on magnet
1-2405 w/2404H-1 magnet (eBay auction)
1-2405 w/ ? magnet (same eBay auction)

I'll FINALLY KNOW what I have...

[ivica]

Eric Sundra at OCS actually has a plastic shim that I made and gave him when I was testing the 075 with the 2405 diaphram.

What is the thickness of the mentioned "shim" materila

[toddalin]

~ four sheets of paper thick.

[Lee in Montreal]

~ four sheets of paper thick.

Which translates into 0.40mm or 0.0155"

[toddalin]

Which translates into 0.40mm or 0.0155"

I found it on-line. It's 0.30mm. They also have 0.20mm and that would work.

I used STSC-2

http://plastruct.com/picat/STRIP_ROD_9.pdf

[ivica]

~ four sheets of paper thick.

Thanks

[ivica]

I found it on-line. It's 0.30mm. They also have 0.20mm and that would work.

I used STSC-2

http://plastruct.com/picat/STRIP_ROD_9.pdf

as i can see STSC-2 is 0.03" = 0.76mm, I think too large??

[toddalin]

Not too large as it worked fine. But you can also go with STSC-1 at 0.5mm (0.020").

[ivica]

Not too large as it worked fine. But you can also go with STSC-1 at 0.5mm (0.020").

I did some experiments,
http://www.audioheritage.org/vbullet...l=1#post319363

and the conclusions are:
- response become "more flat" BUT
- High Freq. bandwidth reduced
- efficiency reduced

[toddalin]

When I was looking into the effects of the shim, I was using a 2402 diaphragm. All the effects you show are above 16KHz and almost above audibility. The 2402 never gets that high to see these differences.

2402 without shim. Note the "hole" we discussed.


2402 with shim. The "patterns" are essentially the same and this may even be a bit smoother across the band.

[ivica]

When I was looking into the effects of the shim, I was using a 2402 diaphragm. All the effects you show are above 16KHz and almost above audibility. The 2402 never gets that high to see these differences.

2402 without shim. Note the "hole" we discussed.


2402 with shim. The "patterns" are essentially the same and this may even be a bit smoother across the band.

Yes I understand that, and interestingly even the dias were different some of the conclusions remain :
-less efficiency
-"flatter" response,
but less UHF part is visible on 2405 dia as been expected too.