Thanks for the suggestions. Do you think I will be able to use for example the JBL 2020 or the Eminence Delta 12 as a direct substitute for the electrovoice EVM12L if I wanted to? Or would I have to redesign the horn on the page in my other post for the new drivers?

Do these sorts of midrange horns need any compensation, or any other filter corrections for the response? (you have told me guitar speakers have a rising response, does the horn correct this?)

Thanks again!
Adrian