Not entirely correct. It would be more accurate to say that they are both Hermaholtz resinators. The slope is not exactly the same, the passive radiators has a slightly steeper roll off than a port.

@@DodgyBrothersEngineering Yes, the PR rolls off with (I think) 30dB/Oct, while the port rolls off with 24dB/Oct. But their working principle is pretty much the same.

@@westelaudio943 I would go as far as saying they work "roughly" the same. A different way to achieve an approximate same desired end result.

@@DodgyBrothersEngineering Well, my main point was, if you want to understand the physics behind the port, it's very helpful to know about the PR first - it's way easier to learn about mass and suspension when present as, well, mass and suspension instead of just air in both cases. Of course both port and PR come with their own quirks design challenges, but today with design software, you can actually design a decent enclosure while still believing a port is just an "air tube to relieve pressure from the cabinet", as many people actually seem to think. Knowledge of the actual physics behind it don't really matter there anymore.

@@westelaudio943 agree, modern software can advise you on things like port air velocity. Which is where most ported designs come undone. I tend to think of PRs as an expensive port alternative that removes a lot of the guess work.

Hell no it's awesome! He's like "Passive radiators, how do they work?!?"

Why?

​@robbielex that video cracks me up 😂

"Its a older meme sir, but it checks out"

Wait till those Juggalo's see it.

But with no magnet how the do magic 😂

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Thanks, makes total sense. I'll avoid them. Thinking about it that way makes me think they're best for things like bluetooth speakers where size and power are big limitations.

Very nice observation. How about both a second woofer and some DSP, together :D.

Weird because the RSW-10 utilizes a passive radiator and that is one of the most accurate and best sounding subs you can come across.

I'd say it depends on the weight and damping characteristics. A small heavy passive radiator will probably swing the longest. A nice big lightweight one like on the back of a Klipsch Forte series speaker, will probably do this less. The best is a sealed horn loaded system, where a compression wave is concentrated and amplified down the horn, and it also takes energy out of the speaker cone, so it stops resonating more quickly - functioning like an aperiodic membrane but with improved efficiency. This is really where "fast" bass comes from. To those who say there is no such thing as a "fast" subwoofer and it's simply that lower notes have longer time periods, the effect is not measured over a single cycle but over several - like blowing into a bottle, it continues to ring for a while. I did have a pair of second hand KEF speakers where the bass did sound fairly baggy like this, though the passive radiators were similar size to the woofers. It is better to have bigger passive radiators that couple to the air better and don't store so much internal energy due to the lower excursion, and also don't run out of excursion and limit themselves as quickly. The other thing a passive radiator will have is a big suckout at its own free air resonance. A port doesn't have its own free air resonance, or it tends towards zero. Although this is usually well below where you should be high passing, you might miss out on a bit of low bass that got through the filter. I have heard from a video review of a certain brand of speakers, that another problem with them is at very low volumes, the rubber membrane can be a bit rigid towards moving at all, so you need to turn them up a bit more than a ported to really "wake up" the bass reinforcement, or else they can sound a bit lacking in low end, as if you just had a sealed box. My opinion is that they have a certain size range of enclosures where they are superior to ported, but then as you get bigger, ported starts to win - losing its disadvantages of the port filling most of the box, or not being able to get the ports wide enough to pass air properly without the tuning frequency getting ridiculously high. I'd say it's rare to see passive radiator designs in PA speakers because the speakers are in the size range where you lose the disadvantages of ports and gain all the advantages.

Correct, you can just buy washers from Home Depot, though each PR usually come with a few to start off. You can use those for size comparison.

@@PartsExpressOfficial Thanks for the reply. I wasnt sure if it would get answered. Some of your Passives do come with a nice set of Weighted Discs most do not. 5mm hole in the Passives. Tuning can be sensitive down to a half-ounce so maybe buy some smaller washers to go along with the larger ones so you can fine tune. Thanks again.

Watch the video, he tells you why.

To drive another speaker, you need another amplifier.

No. People talk about the phase of the PR, but that talk is often misleading. At low frequencies the PR is the main source of sound output, and at high frequencies the active driver is the main source of sound. So the PR is not producing sound that is interfering with the active driver.

I think larger lighter passive radiators generally ring less, but an infinite baffle with a long foam stuffed tunnel on the other end will ring the least - at the cost of efficiency. A fully sized front loaded horn will do well too - due to the air pressure mating improving efficiency, but also drawing energy from the moving cone more quickly in a way that it stops resonating quickly. The room you are in can ring too, and that is often the worst offender of the lot!

Maybe it should be called an indirect radiator?

O and if it is hooked up the polls would have to be switched

Nope. A disconnected speaker has a damper aka a spider that has more rigidity. Some passive radiators have spiders to help with cone alignment but for the passive radiator to work properly it must have as little resistance as possible. The goal is to have as little resistance as possible but the proper mass to equal the desired tuning.