Why so few speakers with Passive Radiators?


Folks,

What are your thoughts on Passive Radiators in speaker design?

I've had many different speakers (and like many here, have heard countless varieties outside my home), from ported, to sealed, to passive radiator, to transmission line.

In my experience by far the best bass has come from the Thiels I've owned - CS6, 3.7, 2.7 which use passive radiators.  The bass in these designs are punchy yet as tonally controlled, or more, than any other speaker design I've heard.  So I figure the choice of a passive radiator must be involved somehow, and it makes me wonder why more speaker designers don't use this method.  It seems to give some of both worlds: extended bass, no port noise, tonally correct.

And yet, it seems a relatively rare design choice for speaker manufacturers.

Thoughts?
prof
I used to own the original Sonus Faber Grand Piano which had a passive front radiator. A small floorstander that was pretty easy to drive but always seemed a bit bass shy to me. Never really fell in love with it and sold it before to long. I know that adds nothing to the conversation and I am at the very back of the bus.
Mainly seen in horn drivers, big woofers Klipsch comes to mind .
Not very accurate that is why most don't use them .

I am almost always impressed by speakers that make good use of passive radiators compared to the competion.

I picked up an 8"front firing Klipsch sub with two side firing passives recently. Was originally looking at much bigger bulkier subs but this little thing competes with the much bigger boys in every way.

I vote for more passive radiators!
A passive radiator is expensive compared to a tube.
It could be a reason why it is rarely used.

With a passive radiator you don't have port noise, but it's not true that there aren't sound at mid frequency that go out from passive radiator.
At mid frequency, passive radiator cone interacts with a woofer cone.
If you use a low pass filter at low frequency you will not have any problems.

With a passive radiator or port you can choose damping of your system and you can get the same result in the listen experience...with an ideal passive radiator!

I don't like passive radiator due to non linearity of the suspension.
Speakers is a really complex non linear system, if we add another non linear component you can loose some performace.

I'm on the bus, too. My Vandersteen 2Cs are a 3-way, with an acoustic coupler on the back of the speaker. Are they considered acoustic suspension? Ported? Sealed?
Thanks for a response, and thanks Prof for this post>

Tom