winkychevelle 10+ year member
CarAudio.com Veteran
OK, OK, OK. Yes, they can play down that low but remember SPL is logarithmic. If my 18 is doing 120db at 20hz and your pair of 6.5's are doing 100, there is literally 12x more energy in that panel.
My 7" drivers are crossed down at 60 and my sub plays everything below. But I can full range them without any real issues.
When you are talking about enclosures and stiffness, its relatively simple physics. The panels need to have enough stiffness to resist the increase/decrease in pressure inside the box as well as resist the forces of the cone/coil moving. My coil windings alone almost definitely weigh more than your entire moving mass combined.
Matt
Ps, yes a box determines frequency response and bandwidth. But you can only move so much air with 6.5" of piston area.
I dont disagree with anything you said here