On the directivity of dipole tweeters

[Rudolf]

Originally Posted by sendler

... 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?

I can't tell you, I can only compare - see diagrams. All measurements are for the closed version of the Neo3 PDR and in infinite baffle. Identical measuring conditions for both drivers, but not done by me.

To put things straight: I'm not advocating to replace all Neo3s by tiny Daytons. I was only trying to find the limit, where dome tweeters can work as true dipoles.

[mondogenerator]

does anyone know of a motorola piezo tweeter source in the UK?
If you remember those 2" piezo cones they did, may youd know where to source them?

Im thinking i might try rudolfs dipole experiment with a pair of those piezos.....

[gooki]

Great thread. This have given me the motivation to test some ridiculously small dome tweeters that I have in a back to back configuration for dipole directivity.

It's the super tweeter shown here, but without the full aluminium housing.

[mige0]

Regarding power handling - one might try to do a dipole ring of that cheap tweeters around the middle dipole - just my 2ct

Michael

[villastrangiato]

Originally Posted by Rudolf

I can't tell you, I can only compare - see diagrams. All measurements are for the closed version of the Neo3 PDR and in infinite baffle. Identical measuring conditions for both drivers, but not done by me.

To put things straight: I'm not advocating to replace all Neo3s by tiny Daytons. I was only trying to find the limit, where dome tweeters can work as true dipoles.

I'm a little confused - is the dual Dayton configuration you've assembled a "true dipole" or "true bipole"? What impact will this configuration have on the "figure 8" pattern true dipoles are known for? Not sure that it really matters.....maybe it's important to some OB purists - I'm kinda green with these dipole and bipole concepts.......

[thadman]

Originally Posted by villastrangiato

I'm a little confused - is the dual Dayton configuration you've assembled a "true dipole" or "true bipole"? What impact will this configuration have on the "figure 8" pattern true dipoles are known for? Not sure that it really matters.....maybe it's important to some OB purists - I'm kinda green with these dipole and bipole concepts.......

Bipole: front/rear drivers are operated in phase

Dipole: front/rear drivers are operated in anti-phase

Both are very interesting concepts.

Implemented correctly, a dipole will provide a figure eight response at the expense of displacement.

I have not seen much interest in bipoles. However, they may offer the opportunity for a minimum of diffraction.

As far as I understand, diffraction is a result of pressure gradients. The sound wave diffracts around the enclosure in order to equalize the pressure gradient. If both drivers are operated in phase, a pressure gradient may not be present. Assuming optimal conditions, the sound waves will support each other and a virtual "infinite baffle" may be created.

Just some thoughts.

Best Regards,
Thadman

[villastrangiato]

Originally Posted by thadman

Bipole: front/rear drivers are operated in phase

Dipole: front/rear drivers are operated in anti-phase

Both are very interesting concepts.

Implemented correctly, a dipole will provide a figure eight response at the expense of displacement.

I have not seen much interest in bipoles. However, they may offer the opportunity for a minimum of diffraction.

As far as I understand, diffraction is a result of pressure gradients. The sound wave diffracts around the enclosure in order to equalize the pressure gradient. If both drivers are operated in phase, a pressure gradient may not be present. Assuming optimal conditions, the sound waves will support each other and a virtual "infinite baffle" may be created.

Just some thoughts.

Best Regards,
Thadman

You're understanding seems to mirror mine. It was not very clear to me exactly what Rudy was producing with the two Daytons - if they were wired out of phase, without some other manipulation of the signal, the apparent phase shift from voice coil centers in different locations would seem to create a response that is other than a "true dipole" - my concept of a "true dipole" is something akin to a single diaphragm or driver radiating in both directions - like most electrostatics. I guess the terminology is more fluid than I thought.

[Rudolf]

Originally Posted by villastrangiato

... is the dual Dayton configuration you've assembled a "true dipole" or "true bipole"? What impact will this configuration have on the "figure 8" pattern true dipoles are known for? Not sure that it really matters.....maybe it's important to some OB purists ...

villastrangiato,
all my configurations are "figure 8" dipoles. But can you imagine a "slim" 8 and a "fat" eight? Many dipoles change their 8 between slim and fat (and vice versa) along their frequency range. Only dipoles, which don't change the proportion of their 8 with frequency, are called "constant directivity" (CD) dipoles.

The purpose of this thread is to discuss the conditions for a true CD dipole tweeter. You could call that an "OB purist thing", yes.

Rudolf

[keyser]

Rudolf, any development here?

[CLS]

Originally Posted by mige0

... one might try to do a dipole ring of that cheap tweeters around the middle dipole ....

Do you mean many tweeters in a ring array surrounding a midrange driver?

That'll be an 'inside out' coaxial !