Why so few speakers with Passive Radiators?

A passive radiator IS a port. As others have said, the enclosure is designed the same way. Here’s why a passive radiator is worse than a port. It has a suspension, so because of that, it is less efficient and can behave nonlinearly. Fast bass? What moves faster, a few grams of air or a few hundred grams of passive radiator? A passive radiator also causes your bass to roll off at a much steeper rate past tuning, 36 dB/octave! Compare that with 24 dB/octave for ported and 12 dB/octave for sealed. This is why it's so much easier to EQ the bass back into a subwoofer/woofer with a shallower rolloff (search "Linkwitz Transform)". The only reasons to use a passive radiator is to make people think the enclosure is of sealed design, make them think there are more woofers or if your port can’t physically fit into the enclosure. Otherwise, a port is superior in every way when designed properly. As far as accuracy is concerned, there’s just no way to beat a sealed design. If you use a port/passive radiator, there will be group-delay near the tuning frequency. Whether that is noticeable is what’s debatable, and apparently, some of you don’t mind or notice. For those that feel that your ported enclosure is "boomy," try lowering the tuning frequency by making the port longer. That might just do the trick.

audioman581 wrote:  " Mainly seen in horn drivers, big woofers Klipsch comes to mind .
Not very accurate that is why most don't use them ."I don't understand this post.  I use horn sub woofers and I consider them the best, most articulate bass of all.  The only downside I see to horn bass is the large enclosure size.  Please elucidate.

Perhaps still a useful conversation, but note the dates folks.  This thread is from 2018.

^Perhaps a bit old, but still relevant.