Wayne Parham Messages: 18835 Registered: January 2001
Illuminati (33rd Degree)
If you want the performance of the four π, you'll have to build a four π. Using another horn or baffle layout may or may not work as well. Most certainly you'll have to go through a design/test development life cycle if you change anything and still want it to sound as good.
I don't mean to be arrogant or dismissive, it isn't that at all. It's just that I've done several designs like this and I have a feel for what changes result when swapping parts, and I also know the amount of effort required to make them right and perfect a design.
The nice thing is it's a pretty simple system, easy to build using inexpensive parts. You've already got the most expensive part - the woofer. So you can easily build the box and procure the horn to build the speaker as shown in the plans. Sell what you don't need and that will help fund whatever you don't already have.