Averaging is sometimes poo-pooed on forums like this. Sometimes for good reasons, and sometimes for not so good reasons. I sometimes find it a useful tool though for better understanding some of the complex resonant behaviors of different audio devices.
This curve represents the average sound power response of a fairly large sampling of different loudspeakers with a flat direct response.
Sound power is one of the components Harman uses to estimate a speaker’s in-room response. And it gives a good idea of what frequencies are more or less emphasized in a typical semi-reflective room. Ideally, the sound power response of a loudspeaker should be pretty close to a linear slope from the F0 resonance in the bass down to the treble. When you start looking at larger samplings of speakers though, it starts to look more like the curve above, with a little dip at around 2k or so, and a bump centered around 6k.
The dip at ~2k is where the midrange driver and tweeter cross over. And the bump at ~6k is the resonant frequency of the tweeter. These features are a little easier to see and distinguish if you remove the slope from the SP curve, which can be done by applying an inverse slope in the +1.0 to +1.5 dB per octave range to the curve.
There is also a little bump in the bass as well, at the resonant frequency of the woofer. (This starts to become more obvious when looking at smaller samplings of speakers, with their own built-in subs. And is usually centered somewhere around 60 Hz, or the resonant frequency of a kickdrum.)
The emphasis in the 6k range is usually no more than a dB or two. And the dip at 2k is probably a bit less on average. Newer speakers with a more linear off-axis response will tend to smooth most of these broader band bumps and dips out though, providing better tonal consistency with the speaker’s flat direct response.