@DonVK: The latest measurements above did not use the old adaptor.
The new conical adaptor with throat insert was designed ground up based on @marco_gea excel sheet mentioned in one of the posts somewhere above. This was the picture sent to me by @WetFartz today morning showing the new adaptor (with ring insert) attachment to horn & driver for above measurements (His earlier pics show a yellow adaptor which has been damped and is now in the blue colored form below).
The new adaptor looks like this and is 19.6cm in length (including the 2cm bottom part that goes inside the driver) compared to the earlier conical adaptor that was 11.6cm in length
How it looked after printing
The adaptor length was determined based on flare rate matching calculations shown below
EDIT: Please find the STL file of the adaptor attached
The new conical adaptor with throat insert was designed ground up based on @marco_gea excel sheet mentioned in one of the posts somewhere above. This was the picture sent to me by @WetFartz today morning showing the new adaptor (with ring insert) attachment to horn & driver for above measurements (His earlier pics show a yellow adaptor which has been damped and is now in the blue colored form below).
The new adaptor looks like this and is 19.6cm in length (including the 2cm bottom part that goes inside the driver) compared to the earlier conical adaptor that was 11.6cm in length
How it looked after printing
The adaptor length was determined based on flare rate matching calculations shown below
EDIT: Please find the STL file of the adaptor attached
@vineethkumar01 , @WetFartz many thanks for trying these experiments, taking all the measurements and sharing the data.
@docali, @DonVK : Thanks for all the help so far 
We tried to make the ring insert such that no part of the slits were covered by the insert and we only change the throat dimensions.
The ring insert was razor thin near the phase plug exit. Its thickness was progressively increased up to about 4mm by the time we were 2cm out from the phase plug exit/slits/driver throat exit.
Here is a view of how the adaptor looks near the slits
We tried to make the ring insert such that no part of the slits were covered by the insert and we only change the throat dimensions.
The ring insert was razor thin near the phase plug exit. Its thickness was progressively increased up to about 4mm by the time we were 2cm out from the phase plug exit/slits/driver throat exit.
Here is a view of how the adaptor looks near the slits
Yes. This is what I did and the length of the adaptor got changed accordingly.
While I'm sanding down the horns and assembling them, I want to get cracking on the bass bin. @vineethkumar01 has been kind enough to share the geometry for the shallow horn. The BR bin would be 100L. Here are a few options, one is a Tannoy, and the other is with a curved side and rear. Which one of these would be best suited sonically with the MK3B2? or would the differences be negligible?
Option 1
Ignore the bracing scheme.
Option 2
Option 1
Ignore the bracing scheme.
Option 2
My preference would be option#2. It's easier to build and brace. I also like the integrated side bevel which can act like a round over. Where is the BR port exit? If you can put it in the front, it will make speaker placement easier.
Awesome work on those mahogany horns. I'm enjoying the pics.
@docali @DonVK Thanks for the input. The port will be in the front.
I'm still trying to figure out how to mount the driver. The driver on the Tannoy isn't sitting flush on the baffle but is instead mounted behind it. Is it okay not to sit flush on the baffle? I understand that if it's okay for Tannoy it's okay for me, but the Westminsters were built in the 80's!
I'm still trying to figure out how to mount the driver. The driver on the Tannoy isn't sitting flush on the baffle but is instead mounted behind it. Is it okay not to sit flush on the baffle? I understand that if it's okay for Tannoy it's okay for me, but the Westminsters were built in the 80's!
If I assume that the acoustic centers of bass and horn are coming closer together this should be more ideal using a passive crossover. In my speakers all drivers are aligned in the same plane of sound origin. But you could look at original TAD design with a Woofer in front of the horn driver the signal from the Woofer had a quite high order x-over to become time aligned.