Constant Beamwidth Transducer (CBT) Speakers

[Bjorn]

No need to get snappy. IR peaks are dominated by HF. So again, can you please share those measurements?

And that matters when the speaker has a constant vertical directivity down to Schroeder? Please explain why.

Ever heard about a bandlimited ETC BTW?

 

[markus]

And that matters when the speaker has a constant vertical directivity down to Schroeder? Please explain why.

That's exactly the question – does it really have "constant vertical directivity down to Schroeder?" Please post data showing this. I can't remember seen it published. Is it somewhere in Keele's papers?

Ever heard about a bandlimited ETC BTW?

Yep, and it's of limited value for showing the claimed behavior with the Schroeder frequency – and a large transition zone around it – usually at around >200Hz in acoustically small rooms.

 

[Newman]

That's exactly the question – does it really have "constant vertical directivity down to Schroeder?"

Yes, pretty much.

Please post data showing this. I can't remember seen it published. Is it somewhere in Keele's papers?

This is from Keele’s modelling:

Keele, A Performance Ranking of Seven Different Types of Loudspeaker Line Arrays, 2010​

He also did actual measurements and essentially confirmed the model for vertical. I need to dig further to find them.

cheers

 

[markus]

Yes, pretty much.

This is from Keele’s modelling:
View attachment 366044

Keele, A Performance Ranking of Seven Different Types of Loudspeaker Line Arrays, 2010​

He also did actual measurements and essentially confirmed the model for vertical. I need to dig further to find them.

cheers

Thanks, remember those theoretical calculations when I read the Keele papers back then. Would like to see Bjorn's claim of "20dB attenuation" confirmed for a real design though.

And again, an ETC won't do even when band-limited. You'll fight frequency vs time resolution and in the end graphs aren't as conclusive as desired. One would need to look at free field data instead.
A 20dB attenuation at a 40-60 degrees angle is pretty hard to do. Something like a Quad ESL-57 does it.