Passive radiator

Were passive radiators an ultimate failure? Does any speaker company still use them? A friend of mine is asking about them in regard to vintage speakers, and all I remember is being unimpressed. But I don't want to tell him that without some back-up.
Passive radiators were and are not a failure. Still used because they offer numerous sonic advantages over ported designs. Their downside vs. ported includes larger cabinet, increased parts costs and harder to properly design.

my fave and reference speaker is the Thiel CS 2.4 or CS 2.7 models. This company still uses a passive radiator in all of its glory. For their particular designs, it works very well. Bass response and frequency range is simply, outstanding. For those whom have a listening space like, 20x20, 25x25 or 30x30...the CS 3.7 is a no-brainer.

Find a local dealer/retailer near you and get yourself a demo. It will perhaps change your view on the Passive radiator. Keep me posted & Happy listening.
The *very* successful GoldenEar Triton series of speakers use passive radiators, apparently to very good effect. This is a well-known technology used by many speaker mfgrs...

Some of my favorite speakers over the years have used passive radiators, though they seem less common these days then back in say the 70's. Goldenear Aon3 is the current one I know of that I have heard and also thought to have top notch sound especially for the price. The combination of side facing passive radiator and folded ribbon tweeter makes these a quite unique design these days at a very affordable price worth auditioning. I've heard Tritons as well and was less impressed, but I suspect the problem was in the specific dealer setup I heard somewhere and not the speakers.
My Def Tech Super Cube Reference sub uses two passive radiators in one box to outstanding effect.Tight and musical to the nines...
My only experience with a passive radiator was the original Vandersteen model 2 which I owned between 1986 to 1994. I never heard this design as a failure.
In the late 70's, at Tech Hifi, among all the major speaker brands and models sold that I heard, my overall favorite for a somewhat larger room were the OHM Hs, one of just a few, and the only OHM that used a passive radiator. They were the ones that did everything right. I think they went for $900 a pair or so back in 1978.

I did not have the right room or budget for those back then so I ended up with smaller ported Ls, which sounded similar on a smaller scale.

I came very close to going with new refurbed OHM Hs a couple years back when looking to bring my setup "up to date" based on the continued strong performance of my Ls, but decided to go with other models that can do the imaging and soundstage deal better than most box speakers from teh 70's.
Hey, thanks guys. He is particularly interested in the Reynolds Advance A-2 and Genesis Physics 3's both I believe from the 70's. Anybody know these speakers?
It's a speaker with all the components removed including the
magnet. It is used to replace a port.
The correct way to design a passive radiator, is to run the
Thiele/Small parameters of the woofer and cabinet internal
volume, for a ported/bass reflex(ie:Fourth Order) alignment,
using the diameter of the radiator as, "port diameter." .
Then adjust the weight/mass of the passive radiator's cone, to
match the mass of the air that would have occupied the
resultant port's volume. A passive radiator should always be
1.5 to 2 times the diameter of the woofer.
The cabinet should be sealed, to avoid noise and messing up the alignment. It will, however, operate as a bass reflex system. "Sealed enclosure" indicates an Acoustic Suspension system.
Legacy Audio also makes use of Passive Radiators with very good results in some of its models....

What is the point and the result of plugging the port on a bass reflex system which some manufacturers have suggested is an option?
Some prefer less bass from their systems. With a rear-firing port; wall proximity can become an issue as well. I used to provide a couple pieces of bonded Dacron, with my vented systems, so customers could adjust to their tastes.