Passive radiators

[Wingman0121 10+ year member]

Anyone running them in their car? How do you like it?

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[T3mpest 10+ year member]

Anyone running them in their car? How do you like it?

I am. I like my setup and it would be impossible to do any other way. I'm using 2 15's tuned at 25hz. The box is only 4.6 cubes, but if I had to try and fit a adequate port, it'd have to be closer to 6 cubes, there is NO way that would fit in my trunk. I'd either be tuning higher than I want to or not having enough airspace. That's the advantage to using PR's other than that it's just like a ported box, it'll just fit in places ported boxes sometimes won't.

 

[Wingman0121 10+ year member]

So one of your 15s is active and one is passive? Do they handle power well or does it unload at really low bass?

 

[T3mpest 10+ year member]

So one of your 15s is active and one is passive? Do they handle power well or does it unload at really low bass?

No I have 2 15 active drivers and 4 15 passive radiators. 2 on the back of the box and one on each side, the actual speakers face towards the back of the trunk. With that much cone area acting as a port excursion is a non issue. Even with 2000 watts applied the passives only move about 10-15mm near tuning. The main drivers are the same way, the hit max excursion at 40hz around 12mm, then the passives take over and start doing most of the work. Tuned at 25 I keep my SSF at

20hz, just like you probably would in a ported design. I'm tuned low enough I dont really ever have to worry about bottoming out, not much music goes below 25hz, but it's better safe than sorry.

 

[RAM_Designs 5,000+ posts]

I've never tried it in a vehicle myself...might want to one of these days. Tempest, are you using the diycable PR's?

 

[Wingman0121 10+ year member]

So to "tune" a passive radiator is to add weight to the PR's cone right? I want to make something as small and powerful as Bob Carver's Sunfire subs(their Super Jr. model would actually fit right under my dash), so maybe a SA8 plus two PR of the same diameter?

 

[ArthurIhde 10+ year member]

Hmmm,never try it.

 

[T3mpest 10+ year member]

So to "tune" a passive radiator is to add weight to the PR's cone right? I want to make something as small and powerful as Bob Carver's Sunfire subs(their Super Jr. model would actually fit right under my dash), so maybe a SA8 plus two PR of the same diameter?

yes. To do that you'd probably position the sub up or down firing and then the passives on both sides. To tune using the exodus audio PR's from diycable.com, which i use, you add and subtract washers attached to a bolt. It's simply a ratio of surface area/weight, just like a regular port. Use can use winisd alpha to model the passives, it's cheap and it's free so then you'll know how much weight you need for a given tuning and what kind of excursion to expect. The one thing I would say with a box that small is that Johns passives from aespeakers might be a better option. Those bolts are very long coming out the back, you may end up with clearance issues between the 2 metal bolts moving back and forth and a magnet right next to it. John uses leadshot to add mass so the weight can't be changed, but you can build the box alot smaller.

I've had some issues with one of my passives, the same one, ripping itself to shreds. I've been through 3 now and I can't figure out how it's happening, but my clearance inside is pretty tight, I think the box may just not be quite a symmetrical as it looks and magnetism is biting me in the ***. It's rather frustrating as the other 3 work fine. The magnets look fine so it's not hitting. I have a hunch though if I change it out for one of Johns who doesn't use a bolt in the back, it won't happen again.

 

[Wingman0121 10+ year member]

I remember the passive radiator that goes with Earthquake Magma subs have a peak excursion of 4", I assume the more excursion a radiator have the better.