I recall my memory from the beginning I jump in this audio hobbies which I should follow to the general audio rules of thumb. Especially for the speaker, the best sound is always from multi-way speakers system. Then if the bass is not strong enough, so adding a sub-woofer or two will improve the low frequency gain. The music can be fine tune as the listener preference with tone control.
I follow this rules for years and at the end it is very complicated. I cannot enjoy the music because I am too busy dial the tone control and adjusting the sub-woofer level. The music is mix with additional noise and dirty from the unnecessary equipment in the signal path. No matters how many times I dial the tone control or the sub-woofer setting, the music never presenting well to my ears.
Until one day, I was thinking about changing my audio system in a simple way. This only the source, it is a CD player, a passive volume control and power amplifier. There is nothing else.
The speaker also very simple, with no cross-over at all. The goal is this system should deliver the sound quality that I wish for. Then this single driver full range speaker project comes in mind.