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What sizing of a Passive Radiator should I use?

Cody AOC

Cody AOC

Active Member
So i have a 15" subwoofer that is 800 watts RMS and a sealed box that is 3.0 cu. ft. and i can't do a ported box since for me it's too complex on getting a low tuning and not knowing what i'm doing for tuning, but anyway i was looking at this psi Passive Radiator https://psicaraudio.com/product/15-passive-radiator/
and they had one that was also for extreme excursion and well i want it to last for a long time i love playing loud bass by the way. https://psicaraudio.com/product/15-high-excursion-passive-radiator/

They do have an 18" Passive Radiator as well if that's what i need?
 
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the rule of thumb I use is two times the surface area of the woofer. I just build a pair of speakers with a 6" woofer and used two 6" passive radiators.
 
You might be able to get away with a 18" PR. I have seen a few designs that use a 15" active woofer and 18" PR. Usually the cabinet is bigger than 3cuft though.
 
You actually need twice the volume displacement, so if the driver and PR have identical excursions, you need twice the area, if the PR has a longer excursion, you need less surface, which is useful.

Also, adding a PR to any given driver isn't always going to work right. In general, the driver must have a Q less than 0.4 to be easily mated with a PR or a vent. Those drivers close to 0.4 or a bit higher are the ones that would require a very long port, and that's where the PR comes into play, as the moving mass of the PR emulates the air mass of the long port in a more compact package.

But the tuning needs to be made. With the PR you can only add mass - or perhaps remove, if the PR has removable weights - to tune.
 
SaSi said:
You actually need twice the volume displacement, so if the driver and PR have identical excursions, you need twice the area, if the PR has a longer excursion, you need less surface, which is useful.

Also, adding a PR to any given driver isn't always going to work right. In general, the driver must have a Q less than 0.4 to be easily mated with a PR or a vent. Those drivers close to 0.4 or a bit higher are the ones that would require a very long port, and that's where the PR comes into play, as the moving mass of the PR emulates the air mass of the long port in a more compact package.

But the tuning needs to be made. With the PR you can only add mass - or perhaps remove, if the PR has removable weights - to tune.
Click to expand...

My driver has a .47 that you said something about it could be close to .4 would need a long port.
 
I have never built a PR speaker but I would think it definitely requires tuning just like a ported speaker would.

BTW, this is not what you asked, but since you seem to have the T/S params for the sub, it should not be that hard to arrive at a ported box design using free box design software like Box Plot. ? Port tubes can be found, they even have telescoping ones that you can set for the proper length yourself. Nothing wrong with a PR design if that's the way you want to go, just offering some info.

PS my Klipsch kg 4.2 use a 10" woofer and 12" PR. The Atlantic Oracle III and IV use 12/12 and 12/15 respectively.
 
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