Passive radiators: what why how???

[Bearcat91]

Well i am in the search for a new set up and recently came across passive radiators and did a little research. I have never heard a PR set up before so im not sure what to expect . I was going to do 2 12s in a ported box but now i am thinking 2 8s and 2 12in PRs like this set up below.....any one hear a set up with PRs? how do they sound?

http://youtu.be/FBJal0iNHOo

 

[badazzbulldog]

I had a box years ago in my 76 gmc that was 2 8" with a 12" pr it sounded good had a 400w amp to it gave a decent thump and fit behind the seat

 

[Bearcat91]

how would it compare to 2 12s or something?

alsi was there any tuning you had to do?

 

[badazzbulldog]

it was a complete box I bought at an electronics liquidation sale,wasnt namebrand subs but for $75 bucks at the time it did alright, there was no tuning involved,also i had this in the early 90's and subs have come a long way from then,if your putting it in your blazer I would personally go with 2 12's since you have the room in the back

 

[Half Assed]

I wouldn't try making one myself. It involves a lot of adjustments on the weights for the PR to make it sound right. It's easier just to make a sealed or slot ported box IMO.

 

[michael hurd]

A passive radiator is similar in function to a port, it has a 'resonant frequency' in the box that extends the output of the subwoofer. It operates over a narrow bandwidth, and can fit in places a normal port cannot: IE, a small box with a deep tune that would require a long, large diameter port that will not fit in the box.

Downsides are steeper roll off than either a ported box, and higher cost. ( about 30 db/octave for a PR box, 24 db/octave for a ported box, and 12 db/octave for a sealed box )

Plus: can tune a small box deep without excessive port compression and / or port chuffing from an undersized port.

Most passives are adjustable by adding weight, and good ones aren't cheap at all. The less expensive ones have less excursion and usually can't take a lot of weight, as the spider and the surround won't support that.

There are modelling programs that can help you model passive radiator or port behavior and tune a box, such as "WINisd" from linearteam.