This design is best when drivers are identical in SPL and Frequency Response. Best if you use dual 12" fullrange.
But if you have a small room, 8" is ideal. The owner of the speaker set up is from Quezon City....ajayxyz11. Congrats bro!
"If it is good sounding in You Tube, it is better in actual listening test." Many foreign audiophiles and speaker companies post their listening test in You Tube to help people have an idea on how their speakers perform.