This is the Altec-Lansing A7 more effectionately know as the "Voice of the Theater". It was a 15" woofer and a 1" compression driver, as is the 4430's and the Summa.

The 4430's were an improvement in that the horn was axi-symetric and Constant directivity, the A7 was not. The 4430's had a better crossover.

The Summa's are an improvement in that the waveguide is not a diffraction device - the 4430's are - and it has a foam refractive plug for even lower diffraction in the waveguide. It has a low diffraction enclosure which is also more solid than either the A7 (which were pretty flexible) or the 4430 (better than the A7. Finally the Summas have a better crossover optimized for polar response not axial response.

So each of these speakers has the same basic design, but each of them uses more up to date technology and theory to achieve a better performance. If you liked A7's or 4430's you'd love Summas.