It is MUCH more complicated than frequency response...room accoustics, dispersion of sound, diffraction of sound, distortion, transient response, cabinet resonance,crossover time delay etc. all play a role. Like enjoying wine...appreciating good sound vs. crap is pretty easy...discerning the differences between good sounding speakers takes a bit more work. There were some studies done in Canada
in the 80's though that DID clearly show that there IS such a thing as one GOOD speaker being perceived as better in blind tests among EXPERIENCED listeners AND that it is possible to design speakers to be perceived that way. A whole bunch of new speaker companies sprang up out of that research
including Mirage, PSB, Energy, Paradigm which today continue to make great sounding speakers...as do many other companies drawing on the same research
and measurement techniques.
Of course, once you have done a great job of creating a near perfect speaker...the kids
will still turn the bass up and us geezers will crank the treble to compensate for our hearing loss.
But...if your question is more like...can I really hear a difference between a $100 speaker and a $500 speaker that have the same frequency response...my answer is ABSOLUTELY.
I refer to HOME speakers above. Boat interiors and exteriors complicate matters somewhat but there is still a huge difference that almost everyone can appreciate between a Crapex 6.5" speaker a good speaker. Just go down to the local Best Buy store and play one of your own very detailed and challenging well recorded CD's and switch between speakers playing at the same overall loudness...(not the same radio
volume setting...the same loudness to your ear). You will hear the difference as you go up in price
generally...but a LOT of car speakers are NOT designed for accuracy...they are designed to sound HOT and give a lot of boom for the buck since the market is kids
. Look to traditional home speaker brands in general for more accurate car/marine speakers.