I believe with the current consumer technology you can spend a little money for measurement equipment to get about any speaker to a ruler flat response on your desired listening position.
After thinking a while, the following ones are the crucial characteristics to look out for in my opinion:
- lowest possible distortion, most importantly in low end - usually made possible with large, heavy enclosures and lots of piston area
- may correlate with the upper characteristic but also: far reaching bass extension
- wide and smooth sweet spot
- short and smooth decay of the whole FR
As long as these fixed values are fine, you can EQ your system to try to achieve 1dB linearity, sacrifice a little max SPL and distortion and have a reference system.
So, as long as you have a miniDSP, AVR or even just a computer the former is pretty easy as long as you have an USB-measurement mic or a spare interface with a xlr measurement mic.
Of course this all only applies to people who care about linearity and want to go through the hassle. So factory-linear speakers will always have a customer base.
Edit: I remember that with the newer miniDSP and some amp you can "activate" any speaker with up to three ways and optimize its performance even beyond the provided passive crossover. You unplug the passive crossover, wire the chassis directly to the amps. The amps to the miniDSP and let the software do it's thing. Boom, hackjob active speaker. Though hackjob may sound mean considering the probably far better result compared to passive.
After thinking a while, the following ones are the crucial characteristics to look out for in my opinion:
- lowest possible distortion, most importantly in low end - usually made possible with large, heavy enclosures and lots of piston area
- may correlate with the upper characteristic but also: far reaching bass extension
- wide and smooth sweet spot
- short and smooth decay of the whole FR
As long as these fixed values are fine, you can EQ your system to try to achieve 1dB linearity, sacrifice a little max SPL and distortion and have a reference system.
So, as long as you have a miniDSP, AVR or even just a computer the former is pretty easy as long as you have an USB-measurement mic or a spare interface with a xlr measurement mic.
Of course this all only applies to people who care about linearity and want to go through the hassle. So factory-linear speakers will always have a customer base.
Edit: I remember that with the newer miniDSP and some amp you can "activate" any speaker with up to three ways and optimize its performance even beyond the provided passive crossover. You unplug the passive crossover, wire the chassis directly to the amps. The amps to the miniDSP and let the software do it's thing. Boom, hackjob active speaker. Though hackjob may sound mean considering the probably far better result compared to passive.