Well I'm not sure how other people would use the terms, but to me "frequency range" implies the span from the lowest usable frequency to the highest usable frequency. Now what one considers to be "usable" is a matter of opinion; for some it might be -3 dB, for some it might be -10 dB, for some it might be something in between.
On the other hand I take the term "frequency response" to refer to the actual measured response of the loudspeaker across the spectrum, but I've seen the term used to indicate the same thing as what I wrote for "frequency range".
Imho, ime, ymmv, etc.
