When we look at the specs for a piece of audio equipment we want to make sure it doesn't emphasize or reduce one frequency area over another. We routinely see flatness specs that are within 1/10th of a dB from below where we can hear to way above where we hear. These specs make us feel good about equipment. Confident.
This is true for electronics but it sure isn't true for loudspeakers. Rarely is a loudspeaker flat to anything better than 2 or 3 dB which is more than 10 times worse than any piece of electronics. Yet we not only accept this as ok, we probably don't give it a second thought because that's just the way it is.
Can you imagine what a reviewer would write about a new amplifier that was -2dB at 1kHz to remove some glare, pumped up to +2dB at 150Hz to give it some warmth in the midbass? The designer would be laughed out of the industry as a nut job.
Apply the same thought process to a loudspeaker and the results are very different: a gentle dip of -2dB between 500Hz and 2kHz can be described as carefully crafted to add depth to the image - a 100Hz to 300Hz 2dB rise adds warmth to a loudspeaker. We applaud this careful crafting of bumps and dips in loudspeakers and ridicule them in electronics.
Here's a thought for you. The flatter response a loudspeaker has the more sterile and unmusical it sounds. In fact, the worst sounding loudspeakers I've ever heard were pretty "flat" where the designer went out of his or her way to reach the mythical perfection of flat.
As designers we want to run through a myriad of different musical examples to make sure nothing stands out: consistently bright, overly warm, too much bass, etc. but that shouldn't mean keeping it flat to a meter.
If it's "good for the goose, why not the gander?" Why are we so adamant electronics must be flat and loudspeakers not?
It's always good to step out of our comfort zones about things we cherish as fixed - like flatness. I am not sure flatness is a great standard.