The icing on the cake

Look at the frequency response curve of any loudspeaker and you'll immediately see it is not flat. Not even close. Deviations in loudness at specific frequencies are denoted in terms like +/- 3dB (on a good day). Some active speakers boast +/- 1dB, but even that's hardly flat. And those measurements have little to do with the actual in-room response at one's listening position. When a speaker designer is faced with the reality of inevitable loudness swings of this magnitude, they can either shrug their shoulders and say that's as good as it gets, or they can use those deviations to their advantage. When they decide to go with the latter decision, the process they use is called voicing. If +/- 3dB is the accepted limitation, designers who understand the art of voicing decide where those deviations are best put to use. Instead of a dip at one frequency, the overall sonic presentation might benefit from a bump in loudness instead. The deviation range remains the same. The sound does not. Not all designers choose the art of voicing. For those that do, it's the icing on the cake.