passive radiator

[DUAL10S 10+ year member]

So my buddy gave me 4 Lanzar max pro 12's. One was blown (froze up) so I built a quick sealed box for the remaing three. Ran them for about an hour and one of them quit working.

I disconnected the sub and put it back in the box. When I played music it sounded ok but was bottoming out. So.........I cut the basket off of it and put it back in the box as a radiator. Quick and dirty but could not leave a 12" hole in the box.

Really surprised how this sounds. I did some quick research on pr boxes and seems to be a lot of math involved to get it right.

Anybody running pr's?

Click to read more...

 

[DUAL10S 10+ year member]

Was playing blueberry yum yum and the radiator was moving so much that the surround started coming off in a few places. Never sounded bad until the surround started separating. Super glue overnight. Guess this is where the moving mass needs to be figured to control the x-max of the radiator.

I can see where things complicated and different power levels and freq levels. If I have read correctly, is this the reason the pr's have adjustable mass?

 

[Rich B 5,000+ posts]

You might need to add some weight to the cone to reduce the cone movement.

 

[Frito11 10+ year member]

i'm no expert on them but a buddy of mine has built one and is designing another right now

1st one he build is a RE SEx10 with a 12" PR, i haven had a chance to hear it yet but he tells me it hits extremely low for a single 10. he choose the sub due to its high excursion.

here is a video of it



hes currently working on a 15" sub pushing an 18" PR. should be done in a week or so.

from what hes told me is pretty much a PR is equal to a port but in place of the length of the port for tuning its the weight of the PR that tunes its resonate freq. the bonus to PR setups is the sub will not unload when it goes under the tuning freq as ported will and group delay is at least slightly better esp around the tuning freq.

 

[hispls 5,000+ posts]

To do it properly you need to have mass equal to the mass of air that would be in a port of sufficient length for your desired tuning with radius of the radiator. You should use about 50% more PR area than cone area of your active driver, and since rolloff below tuning is much sharper than with a vent you should be using subsonic filter.

 

[T3mpest 10+ year member]

What your trying wont' work. You need 2x the amount of surface in area in passives as you have in subs. Plus without adding alot of mass that passive is far too light and probably tuned at 150hz lol. It'll bottom out and rip no matter what you do. Keep the sub in place so that you wont' have a hole in your box, but if you want to do an actual PR setup you'd have to buy an actual passive radiator or 2.

 

[i2ain2thunder 10+ year member]

To do it properly you need to have mass equal to the mass of air that would be in a port of sufficient length for your desired tuning with radius of the radiator. You should use about 50% more PR area than cone area of your active driver, and since rolloff below tuning is much sharper than with a vent you should be using subsonic filter.

This. PRs are uaually expensive too, the right one will prob cost you more than another sub?

 

[Kangaroux 5,000+ posts]

adding mass to the PR will reduce movement but it will also lower your tuning significantly