# Passive Radiator use in car?



## demon2091tb (May 30, 2005)

I've done a good deal of searching about passive radiators use in car, but i keep coming back to the though of the movement of the car that could possibly ruin the PR.

I would like to know the Advantages and Disadvantages of a PR over a typical low tuned ported box, and a Sealed box. As i'm mostly thinking of going the PR route, but have heard about Fluttering noise associated with the Passive radiators.

How do you figure up the size of the enclosure to use with a particular sub, and how much mass to add to the PR to tune the box to a certain frequency? As well as what direction does the PR need to be facing to get the best sound.

I ask the Direction question because i had initially thought of using a single 15" Tempest, centered in the rear and f-glassed, but i would still like to keep the box size to a minimum, and would still like the output of the Ported enclosure with the size of a sealed enclosure, and read about the PR having a very good sound, low extension like a ported box, and getting very loud possibly as well. But i would still like to keep the design the same, and either put the PR beside the 15" facing to the rear or put it on the front of the f-glass box facing the rear seats.

Any thoughts or opinions....as well as usefull info about my situation/needs?

BTW thanks to anyone that reads this thread. :?:


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## Derek (Jun 4, 2005)

well....you usually want to have roughly twice the Vd of the active driver...and it sounds like you're only using one PR? probably going to need two or you're going to risk smashing the hell out of one of them 

pr's can work fine in the car....i wouldn't worry about the car movement doing anything to the PR....they are floppy....but not "that" floppy.....should be just fine...


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## 87DXHatch (Jun 25, 2005)

demon2091tb said:


> I've done a good deal of searching about passive radiators use in car, but i keep coming back to the though of the movement of the car that could possibly ruin the PR.
> 
> I would like to know the Advantages and Disadvantages of a PR over a typical low tuned ported box, and a Sealed box. As i'm mostly thinking of going the PR route, but have heard about Fluttering noise associated with the Passive radiators.
> 
> ...


Everything I've read about using them in a car talks about the possibility of messed up sound with the PR moving in and out due to car movement, but I don't know if this is an actual problem of just perceived as one.

Really, the only advantage I've ever heard of with using a PR is that you don't have any port noise... in the already very noisy environment of the moving car, with a subwoofer in the trunk, port noise is usually a non-issue.


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## demon2091tb (May 30, 2005)

So rather than going the PR route....would you suggest a moderate sized ~4cf ported box tuned low ~25hz or a sealed box. My goal is the best possible SQ with really really good extension, very flat response, and the ability to still get very loud.


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## Drumah (May 18, 2005)

Maybe you should try a sealed box? I think a tempest would have to much low end for my tastes in a car.


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## npdang (Jul 29, 2005)

PR has much greater surface area than any port.... = more linear at higher output, and less compression... frequency response won't change, lower distortion, and more output.

Also saves space since you just stick it to the side of a box. I don't see any issue with using them in a car, even though they are a bit floppy it's not THAT bad. Kind of like all those bad threads you read about ribbons popping from just shutting the door, yet somehow team toxic bass ran 150db in their car without any problems....

But, if you want the flattest response and quickest transients (LOL like it matters) you're probably better off with a really small, high q alignment sealed box.

My response isn't even flat, it's a good +~3db rise or so toward 20hz and people have commented that it "lacks low end".


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