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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
beetlemania
834 posts
 
Everything is a trade-off in speaker design. If there was one "right" way, all speakers would share that design! Each designer weighs the trade-offs to optimize what they think and feel sounds best.

Sealed boxes tend to give the best definition and resolution but at the expense of extension and ability to play loudly. Ported designs, including Thiel's radiators give better extension but at the expense of low bass timing being a bit slow.

One "good" source of info is the Audio Perfectionist Journal, archived on the Vandersteen website (under Resources, Richard Hardesty memorial). In particular, I suggest Volume 3 for trade-offs of vented and sealed enclosures. (I would add hot links but Audiogon's link feature does not work for me).
prof OP
3,471 posts
 

Thanks, I’m aware that everything is trade offs, but the passive radiator seems such a successful trade off I’m intrigued that it’s not used more, vs the much more common trade off of, say, ported.

Having owned and listened to many sealed designs, I don’t find the passive radiated Thiel bass remotely describable as "slow." It’s completely the opposite.  I've searched in vain for other speakers with as tight, tonally controlled bass as I hear from this passive radiator design.
beetlemania
834 posts
 
I agree that it is a "successful" trade-off and I am plenty happy with the bass performance of my CS2.4SE. But I think you need to directly compare sealed vs. vented (including passive radiator) designs to fully understand the what the trade-offs are. Most designers have much more experience with this than me and, presumably, you.

In the case of Thiel, it could be instructive to compare the bass performance of the sealed box CS3.5 with the vented CS3.6 (I've never heard either model). I have no idea what Thiel's rationale for the change was but, clearly, he thought the trade-off was worth it. The dearth of other models with passive radiators suggests other designers hear it differently.
pops
2,273 posts
 
beetlemania the 3.6 is not vented unless you consider the passive radiator as the vent.  It is a sealed enclosure.
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