Passive Radiators?

[Justin braaapp]

Thinking of switching up my one 15" sp4 for two 18" hdc3's. My question is would I be able to fit two of them in an extended cab Silverado 1500 if I used passive radiators? If so what size and how many pr's would I need and what size would this box be? any help you guys can give me is much appreciated!

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[mlstrass 5,000+ posts]

Those subs like large enclosures and lots of port area. Highly doubt a PR would work....

 

[T3mpest 10+ year member]

Those subs like large enclosures and lots of port area. Highly doubt a PR would work....

It could be done, but he'd want quite a bit of them.. If you went with 2 18's, he would want 4 18 inch passives and possibly not have room to fit them.. Other issue is while the HDC's can play well under tuning passives won't. They roll off a little harder than a ported box would and can be mechancially damaged. You'd want to make sure you use a SSF for that reason.

Anyway it would save you all your port displacement, if you can fit that on the other faces of the box. HDC 18's like what, 8 cubes net each? You'd still need 16 cubic feet then give or take a bit.

Anyways OP.. That should answer most of your questions.. IF you can fit subs facing up and then do 1 passive on each side, that'll cancel out their vibration when they get moving. Probably want to invert mount the subs, to give youself room in the box for the passives depth.. I once did 3 passives all facing rear and the passives were strong enough to move my box across my carpet.. It was 9 cubes of double layered MDF with a 50lb sub in it, well over 200lbs, slid it like it was easy lol.

 

[gckless 5,000+ posts]

Yeah, you're looking at 4 18" PRs. You want NO less than 1.75x the Vd in the PRs as in your powered drivers, and closer to 2 or more. Surface area may kill you here, but with a box that big I'm sure you can get two on one face and then one on each side. It can be done, just gonna have to take some maneuvering on your part.

And yeah, as T3mpest mentioned, PRs rolloff real quick. Like, basically don't plan on playing anything below tuning if you're running high power and on the edge of barely enough Vd.