I am planning to biuld a 2397 horn for my 2420 driver .

I do have drawings for a 130 ° horn , 5 island 21°67 each other and i need advise for the following .

1. Should I varnish or not inside of the horn ( better or not for the sound ? )

2. I have to make an adpater like 2328 I believe from 1inch round to 4 inch square ( 10 cm ) about
It should be in wood as I can't get original .

An otehr option would be to make a direct opeing 1 inch on the horn instead of 4 ich square but i ma afraid the opening would not allow the air and sound to go in all the side of horn ; wiht zn adapter it would open better the diffraction !.

Any advise .

Best regards

Gerard