Why so few speakers with Passive Radiators?

tomtheil wrote:

• whereas deep bass benefits from near-the-floor coupling.

This is one reason I’ve viewed some of the many boutique speaker platform/feet with a bit of suspicion. Many report sonic change in their speakers upon using these feet, but it seems obvious to me that raising the speaker off the ground is going to change the relationship of the bass with floor coupling and...change the sound. Not to mention raising the mid/tweeters higher in relation to the listener’s ears.  This is changing the, I presume, from the floor relationship the speaker was designed for (placement of woofer height relative to ground, etc).

So it’s not surprising sound will change...but...for the better? Haven’t you changed the relationship the designer created with the floor to something else?

I recently tried some iso-acoustic iso-puck footers under my Thiel speakers and found pretty much those changes - a change in bass and the high end/mids. The bass actually because a bit more "overhang"-like and fluffy, and tightened right back up again when I just put the speakers directly on the floor. (I’m not using spikes).

Though, on the other hand, I’m wondering if speakers are generally voiced with spikes underneath? If so, I suppose as long as new footers don’t alter the height beyond what you’d have with the spikes, it should be a detriment to the sound.

Tom,
I got lost with sealed box and transmission line. How do you have both? Aren't all transmission lines open box? 

Do you mean a sealed box, equalized within a transmission line? I guess that would make sense?
This would be only for the very, very low frequencies I assume.
I have always liked transmission line bass. Very relaxed and effortless.

I have had virtually every flavor on the market, since 1956. Planar, electrostatic, loaded, ported, open air. It is my feeling that, while the loaded are power shy I find the ported boxes offer some Chuffing. I find this disconcerting. Currently I am happy with the 3 individual enclosures per side, 2-6 inch Scan speaks per box, for a total of 6 small woofers per side to be quite rewarding. Quick, powerful,authoritative and natural. No lumbering giant cone, no vent. I may stay with this configuration forever.

Speaking of the east coast sound pat5jfet referred to, I have a pair of EPI 200C's I picked up for cheap a few years ago from the original owner that bought them in the 70's, like new grills and cabinets. I can't remember the details of the history, but I recall Genesis factored into the lineage somewhere. A fellow named Huh Powell was once associated with one or both of the companies and still provides parts and service for the brands in New Hampshire. I bought updated jack panels/crossover caps for the 200C's couple years ago. With a big passive radiator, 12" IIRC, and the inverted dome tweeter they are very nice sounding and doing active duty in my third system now.