At right is an anechoic frequency response graph from SoundStage!. For our purposes, wondering which speaker it belongs to is irrelevant though certainly no secret. In the absence of boundary reflections i.e. 'room gain', the same sub 100Hz response drop would also show with other speakers.
From this graph, you'd say that our mystery speaker has no bass. If set up deep in a back yard, that'd be true. Once enclosed in a room however, the longer wavelengths wrapped around the speaker cab are free to reflect off our six primary boundaries of walls, ceiling and floor plus assorted furnishings within.
Like mirrors do for light or the glossy reflectors inside lamp shades, reflections amplify sound. They add themselves to the music signal. Speaker designers account for this in their tuning. They expect this free extra acoustic gain to sum to their desired final response.
The upshot is that from this type graph, we can't predict how a speaker will behave in-room relative to bass. This graph only shows that the speaker designer expects room gain to actually start at 200Hz so begins his roll-off there. He probably relies on close-proximity boundary gain for the intended summing. That might predispose this speaker for smaller rooms set up close to the front wall. What'll exactly happen in our room is of course anyone's guess; including his. He can only account for typical i.e. averaged room gain. The rest is up to the pecularities of our space and setup.
This doesn't impugn the utility of such graphs. Rather, it illustrates why covering the sub ~100Hz band with a separate bass generator aka subwoofer removes the biggest variable in speaker sound. Now a sub becomes a quasi equalizer. Speakers will still sound different, just a lot less so. Obviously that's predicated upon the subwoofer's response having been linearized and set appropriately for our room. Unless our sub is of the very rare Ripol type below to cancel most room gain, adaptability by way of user adjustments is key to compensate for our room's response aka interference.
Another way of saying the same thing is that if a sub takes over the bottom two octaves and successfully banishes typical room issues, the remaining differences between various speakers stand clear and clean. They're easier to hear because the biggest difference and sonic confusion has been eliminated. Also, they now matter very likely less. Rather than being decidedly better/worse, they now often are just a sideways move into a different flavor. Put blunt, a cheap speaker with unproblematic bass will always sound far better than a luxo speaker with problematic bass. Yet without all the necessary adjustments of active bass, fixed passive bass typically is problematic. How much money you spend on it doesn't really factor.
This is yet another argument why the consideration then control over how bass and room interact is so primary. Sort that and you've cleared the probably biggest hurdle to good sound.
