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There's lot of knowledgable folks who hang out here and so I thought I'd post a general speaker question -not specifically high eff, but what the heck. Anyway, I was thinking this morning of my old pair of RTR speakers I had in the 80's (ex-wife now has them, but foam surrounds are rotted and one tweeter blown). These were basically a 2-way with IIRC, a 10" woofer and dome tweeter, but they had a passive radiator. So I started wondering why we don't see too many (any) designes anymore that sport either an aperiodic vent or a passive radiator. Is it too hard to model the box? Seems like both of these accomplish stuff that vented or sealed can't do. I know parts are available, but I don't see much discussion or development using these technologies. Thoughts? Oh, and while I'm at it, I read someplace that Dynaco, in developing their A-25, tuned the stuffing by some means of playing a square wave (I think) and monitoring the output of the speaker? How does that work? Would it make building aperiodic easier/ more accurate? Inquiring minds want to know...
A passive radiator can be used for tuning a box lower than what would be possible with a port due to size constraints. I haven't studied their potential advantages and disadvantages, but I would expect proponents to say the lack of vent turbulence and the ability to tune deep are its two biggest advantages. AE Speakers makes passive radiators. Nick McKinney seems like a pretty good guy and I think he is very quality conscious. So you might check out his products. Nick used to spearhead Lambda Acoustics, and AE speakers appears to be pretty much the same thing. I don't know what happened to Lambda Acoustics, but I know they closed several years back and are now doing business as AE Speakers. The technical design principles appear to be very good, using things like shorting rings and cooling plugs and concentrating on cone and spider material for reduced breakup on extended bandwidth drivers.