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Passive Radiators - What Happened?

Wigwam Jones

Wigwam Jones

Caesar non supra grammati
I noticed recently that some of the mainstream speaker manufacturers seemed to have been enamored of large passive radiator designs for a short period of time in the mid 1980s, but then they dropped out of favor again.

Specifically, I noticed Infinity, Polk, and KEF, all well-known if not top-shelf speaker manufacturers, who had passive radiator designs in the respective TOTL speakers during that period. Klipsch is another brand that used passive radiators extensively, most notably in the KG2.

So what's the deal with passive radiators? A fad that came and went? A good design that was surpassed by better designs? A good idea? A bad idea?
 
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Wigwam Jones said:
I noticed recently that some of the mainstream speaker manufacturers seemed to have been enamored of large passive radiator designs for a short period of time in the mid 1980s, but then they dropped out of favor again.

Specifically, I noticed Infinity, Polk, and KEF, all well-known if not top-shelf speaker manufacturers, who had passive radiator designs in the respective TOTL speakers during that period. Klipsch is another brand that used passive radiators extensively, most notably in the KG2.

So what's the deal with passive radiators? A fad that came and went? A good design that was surpassed by better designs? A good idea? A bad idea?
Click to expand...

goodmans made a passive radiator model dimension 8 .i also would like to know if that idea is good or not??
 
Still in use here and there.

One notable current example- the Tannoy Precision 6.4. A 6.5" dual-concentric, a 6.5" woofer, and two 6.5" passive radiators. Serious horsepower in a slim package!

Regards,
Gordon.
 
I think there were a couple factors, one being a trend toward compact systems in the later 80's, and the other being the evolution of technology.

Tech advances, particularly with regard to computer aided design tools and modeling programs allowed manufacturers to do more with less, passive radiators and the extra cabinet size/volume they required fell out of profitability.
 
In the old days there were also bookshelf speakers with 8", 10" and 12" woofers. These were all replaced with 6" max woofers and subwoofers. I think the same applies to passive radiators. They were typically in larger boxes. The boxes shrunk and subwoofers added the low end.
 
I loved my Genesis speakers with passive radiators. They were similar in size and price to Large Advents but with IMO better bass and midrange performance.

My guess is it costs way more to do a passive radiator than a hole with a piece of tube installed. As long as the port dimensions are practical for the cabinet size, you don't need a passive radiator. Economics are tougher today than in the '70-80s and passive radiators became a bad economic decision.
 
Manufacturers have gotten better at cheap but well-designed flared slot ports, and that probably eliminates a few passive radiators from the field, but it seems like there's still a lot of them around to me. Some companies using them today:

Mackie
Tannoy
Polk
KEF
Theil
Wharfedale
Totem
Martin Logan
B&W
B&O

I could go on... :D
 
Interesting thought, that there might be nothing inherently inferior about passive radiators, but that they may simply have fallen victim to more popular smaller boxes, subwoofers, and the economics of making a port instead of a radiator. I admit, I had not considered that.

It might seem then, that some of the 1980s designs might be worth revisiting for the DIY guy, presuming that they didn't have the same size/price requirements.
 
I agree it's probably a size issue. My JBL L150's (only pair I have with a PR) are definitely the largest of my three JBL pairs, but not necessarily the most powerful.

Other downsides are, an additional cone that needs to be refoamed.

Plus side is that it's easier to tune. My L150s have mass discs on the rear of the PRs. More weight extends the low-end response. Less weight gives it boomier (though less extended) bass. It's a lot easier to add or remove mass discs than try to adjust the port length...
 
Cutting a hole in the box is cheaper than a passive radiator, for most companies it makes better economic sense.
 
Here's a passive radiator used in the 1971 Bang and Olufsen 5700 Studio Monitor.
It's built like my Celica spare tire.

A 15" passive radiator used in the 1969 JBL Sovereign S8R.
 
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simple, home theater systems introduced the powered sub into almost every home.

also, from a DIY perspective, trying to tune a PR is much more complicated than tuning a port. one less variable to look at: the port doesn't move.
 
bowtie427ss said:
..Tech advances, particularly with regard to computer aided design tools and modeling programs allowed manufacturers to do more with less, passive radiators and the extra cabinet size/volume they required fell out of profitability.
Click to expand...

actually just the opposite is true for PR alignments. they were implemented originally to reduce cab size for a given target fs.

actually see a lot of PR designs. Def tech abandoned their novel 'synthesized transmission line tuning' in favor of PR and Goldenear uses them extensively.

i think the main issue for manufacturers is cost and especially shipping cost. those weights in the PRs add to the already sky high shipping costs.
 
I still have my big ole Cannon TLS towers with passives from the 80s. Still a nice sounding speaker.
 
I still like the sound of the older speakers with PR's. Of the few sets of speakers that I have rehabbed, half of them have PR's. Genesis II, ESS PS-8 and I'm currently working on Klipsch KG-4's. I didn't start out looking for them particularly, but I find their sound very pleasing.
 
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