How many 6.5in driver equals one 8in driver

Probably an easy question but the answers are even more complicated.

Larger bass drivers are always better but the audio manufacturers went to smaller sizes about a dozen years ago because people wanted to fit their speakers into their rooms and because it was an opportunity for manufacturers to begin selling subwoofers. Subwoofers after all are meant to deal with inadequate main speakers it's that simple.

I guess it depends on what you mean by “equals.”

alright smart guy, two 6.5" drivers are equal in area to one _____ dia.?

I like math problems. The answer is 9.19" so I would say a 9" woofer rounded down or a 9.25" woofer rounded up would be closest.

A local dealer/builder utilizes single or twin 18” woofers in his custom speaker builds.  These woofers are custom-made for him to be very fast low-excursion drivers.  He claims that his twin 18” models go down to 35 hz.  Truly deep bass is not one of his priorities and he hates subwoofers.

My own speakers don’t go deep either as they are also low-excursion; they utilize twin 12” alnico magnet, paper-coned, pleated paper surround drivers designed to match very fast compression/horn midrange drivers.

Size isn’t all thst matters.