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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
davide_845
1 posts
 
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.

tomcarr
1,500 posts
 
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
rodman99999
6,125 posts
 
Systems utilizing passive radiators ARE, "vented" systems. The Thiele-Small parameters and calculations, are identical for both. Only the application(vent or radiator) of the results(mass of port air/size and weight of the radiator), varies. https://itstillworks.com/size-speaker-enclosure-passive-radiators-7918995.html   "Tighter" bass can be realized, by adding weight to the radiator(s).
tomcarr
1,500 posts
 
Sorry, forgot to ask is an acoustic coupler the same as a passive radiator?

Tom
beetlemania
834 posts
 
The 2Ce and 3A use sealed enclosures (I think the Treo has a downward firing port). From Tom Norton's 3A review in stereophile:
A cutaway photo reveals four drivers and three separate sub-enclosures—the bottom of which is the largest, for the rear-facing 10" driver that Vandersteen refers to as an "Active Acoustic Coupler." It is, as the name implies, actively driven [though it shares some of the characteristics of a passive radiator—Ed.]. Since the AAC is designed to cover primarily the range below 35Hz, I would be inclined to call it an integral subwoofer; but perhaps Vandersteen chose to give it another designation to distinguish it from the company's dedicated, outboard subwoofers. 
I think the crossover is designed as a 3-way, so not sure how this thing works - and I ran 2Ce Sig IIs for 10 years! Maybe the filter for the woofer has a sub-network for the AAC?
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