One of Fender's most popular bass cabinets in the 1970's when I played regularly had two 10" drivers which produced plenty of bass. Now I get the argument that this would not be a direct comparison to high-fidelity speakers, and in particular these were made to fill a fair-size club with bass not a small room with precision sound, but you can have good bass with drivers that aren't 15".
Demise of bass quality in Main speakers
When I was shopping for new speakers in addition it became quite clear that modern day main speakers are being made with smaller bass drivers. And to get larger bass drivers you have to go up to alot more expensive models and still they or on the small side.
The Industry came up with a solution for bass challenged main speakers - buy two subwoofers to solve the problems of the modern age main speaker. And subwoofers now being sold in pairs have 8 inch or 10 inch driver sizes, which are still not big enough unless you spend a lot more money.
I bought a subwoofer with a 12 inch driver 20 years ago, thankfully. When I looked at the newer subwoofers the speaker manufacturer told me that he gets many comments stating that the fullness and rumble ability of modern day subwoofers have been substantially diminished, and he agreed. Isn’t this what subwoofers are all about. Why would I need a subwoofer for better define the lower base area. Fortunately I bought very nice main speakers which had a range spec down to 20 Hz and the bass driver size is 8 inches but I had to pay more to get this larger size.
Why do people put up with this? Put larger bass drivers in Main speakers and then you won’t have as many people complaining about Poor bass quality. Doesn’t this make sense?