I am calling attention to this review because the loudspeaker at issue is very straightforward, and therefore it will be rather easy to design DIY versions of it.
https://trackingangle.com/equipment/philharmonic-audio-the-true-mini-monitor-loudspeaker
The drivers are the SBA 4in-SB12PFCR25 woofer and the SB19ST-C000-4, .75-in. dome tweeter.
Cabinet volume is 8 Liters.
My review starts out with one of my funniest audio stories.
Note, the cocktail stirrer straws are not Factory.
john