On the directivity of dipole tweeters

[Rudolf]

Originally Posted by mondogenerator

mow i need to learn more German so i can try an do some interesting sims too as i only use as much as i understand in german language

I'm taking my hat off to any foreigner who is trying to understand Boxsim in German!
The text in Boxsim would be foreign language for most Germans too.
There has been some initiative to get an english version of Boxsim. Trouble is that the complete text is imbedded in the code - no separate language database. So UweG - the coder - shies away from excising all those textstrings.

[LineArray]

Originally Posted by keyser

...
Perfect dipole treble seems impossible in the real world
...

With distributed mode transducers one can get larger than wavelength
without beaming. Dipole radiation is a natural way to use a DML.


Kind regards

[Rudolf]

Am I completely nuts?



I cut the front plates of two Dayton ND20FA to the minimum and glued them roughly together without any baffle. You can compare the size to the previous baffle above. Dipole length now is 3.1 cm.

Then the same horizontal measurement procedure as before:



Since I could not believe what I saw, I did the same for the backside of the dipole tweeter and moved to the other 90deg side:



Green lines are for power response. Don't know why the 75deg response for the first diagram did not come up like that for the second series.

Tell me that this can't be true. Both drivers together are under 19 Euro. One BG Neo3 is 79 Euro in Germany.

[LineArray]

Hello Rudolf,

this is a really impressing - and cost efficient - result !

For vertical angles i would expect some more disturbances,
but when that configuration is mounted at the right height
that should be neglegible in practice.

Kind regards

[Saurav]

Wow, that's really impressive. And just when we'd all agreed that dipole up to 20kHz was impossible

[catapult]

Nice Rudolf! Can you remove the front plate from the ND20 to cut it down or do you just mask off the dome and cut it?

[CLS]

Will this be a little more 'convenient':
Parts-Express.comayton ND16FA-6 5/8" Neodymium Dome Tweeter | tweeter nd16fa-6 soft dome tweeter dome tweeter neodynium dayton audio dayton loudspeaker dayton

or this:
Parts-Express.comayton ND20FB-4 Rear-Mount 3/4" Neodymium Dome Tweeter | tweeter nd20fb-4 soft dome tweeter dome tweeter neodynium dayton audio dayton loudspeaker dayton zdt35-60608 POTT-080108 DayAudiTweetWoofMid050109

[jerome69]

Originally Posted by Rudolf

One BG Neo3 is 79 Euro in Germany.

You can get it for 49€ in France
It is rare that things are cheaper in France.

[Rudolf]

Originally Posted by Saurav

Wow, that's really impressive. And just when we'd all agreed that dipole up to 20kHz was impossible

Yeah. When I started with cutting the drivers front plate, I expected to push that dipole irregularity 0.5 kHz up at the upmost. Really did not expect it to almost vanish. But obviously those last mm can make a vast difference.

Originally Posted by catapult

Can you remove the front plate from the ND20 to cut it down or do you just mask off the dome and cut it?

No removable front plate. But you can easily saw or cut around the magnet housing from the backside. Quite soft plastic, no danger of anything chipping away. I did mask off the dome, yes.

Instead of simply glueing the drivers together - as I did - it could be a good idea to make a pair of mounting flanges like this:

Originally Posted by CLS

Will this be a little more 'convenient':
Dayton ND16FA-6 5/8" Neodymium Dome Tweeter
or ... Dayton ND20FB-4 Rear-Mount 3/4" Neodymium Dome Tweeter

Not really. The ND16FA is just a 16 mm instead of 20 mm dome in a housing of the same size. That is no deal IMHO.
The ND20FB-4 is larger in both directions. Both tweeters have more of a waveguide in front than the ND20FA. I fear that they might develop some sort of horn directivity before the dipole directivity disappears.

Originally Posted by jerome69

You can get it for 49€ in France
It is rare that things are cheaper in France.

Thank you, nice to know. The German import only sells a special PDR-I version.

Originally Posted by LineArray

Hello Rudolf,
For vertical angles i would expect some more disturbances,
but when that configuration is mounted at the right height
that should be neglegible in practice.

The vertical distance of the drivers is 2 mm less than in the previous version. So the vertical balance should be no worse than before. I will do new measurements some time this week.

Thanks to everybody for your appreciation of my work
Rudolf

[sendler]

That is a great pattern but how much of the already minimal power handling and low frequency extension will remain after EQ to even make it to a 3k crossover?