My favorite example of this kind of frequency response spec is Grado. As you move up their product range, they advertise a larger and larger range of frequencies, from 20 - 20,000 on the SR60 to 5 - 50,000 on the PS1000. The actual extension is
virtually the
same. Both are down to about -40 dB at 20 Hz and -35 dB at 20 kHz. And neither is exactly linear at any frequency. It's even more controversial because they've always been rumored to use the same drivers throughout most of their product line, and indeed the SR225 measures
nearly identical to the PS1000 when equipped with the same pads.
If you still think this spec means
anything after seeing that, you're being silly.