Passive radiator ?

Low price makes it more feaseable.

https://www.parts-express.com/define...ator--299-4054

Ever wanted to try a PR with subwoofer , instead of port/vent ?

Looks good to me ?

For ultra-compact enclosures , 20 mm excursion , $25 , rubber surround , 12 inch diameter [ 10 inch sub would work with this ] ! and a 'half-an-octave' lower output !

Isobaric ( 2 subs needed and power for both , literally cuts box size in half )?
Could shrink volume needed even further , whilst removing distortion ( odd order )!
https://images.app.goo.gl/bPkqiPmBqAVzNPmR7

I ordered 2 of these, going to do some experimenting. TI will probably be a month or two before I can get to it.

Diy Audio Guy ,

Excellent ! Good luck and let us know what you think !