Passive Radiator

[Suicide Bobb 5,000+ posts]

Just picked up another Boston GTR 12" for $25, bnib! Needed to kill time before work, so I decided to check out the local Stereo King just for fun. Turns out they had a "garage sale" going on. Nothing really stood out, until I got to the very end of the room and saw that little gem sitting there for $25 //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

What should I do with this one? I now have two of them. What if I used them in conjuction with my Earthquake DBXi10s in a bandpass enclosure, where the subs are inside the box facing towards the port which will fire into the cabin, and the passive radiators mounted on the rear baffle firing towards the trunk? Would that be redundant, or would it allow me to reduce the enclosure size like I was hoping to do? My trunk has a little "step-up" on the north-end, likely to clear the rear differential. It is maybe a foot and a half deep before it steps down, so I was hoping to fit a proper enclosure that just sits on that little step-up portion.

I understand that Passive radiators are meant to be used in a sealed enclosure, which will net the gains of a ported box in a smaller package, but considering that bandpass enclosures are like sealed boxes within a ported enclosure, that should still work as intended, right? Sorry guys, I'm a box noob //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

If that isn't a good idea, what are some other ideas you guys have? I've got plenty of things to toy around with, including my Eclipse SW9122 that's on its way to my house (thanks UMWdawg!) //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

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[winkychevelle 10+ year member]

Yes u can use a pr in place of the port on the ported side of the bandpass enclosure. I'm actually wanting to do this in my car yet pr's are hard to come by around here and new they seem to be pricy

 

[Suicide Bobb 5,000+ posts]

Yes u can use a pr in place of the port on the ported side of the bandpass enclosure. I'm actually wanting to do this in my car yet pr's are hard to come by around here and new they seem to be pricy

I don't want to use them in place of the port. My goal is to port into the cabin through the center pass because my rear seats don't fold //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

I want the PR's to be mounted on the back panel of the box, facing out towards the trunk. The subs will be mounted inside the box, facing towards the port, which will be firing into the cabin.

 

[Phoenix Risen 10+ year member]

your almost getting into the realm of 6th order, or at least it sounds like it.

 

[winkychevelle 10+ year member]

Then it would be a sixth order bandpass and not a fourth order. IMO I think that you probably shouldn't do this because sixth orders are hard to calculate and easy to screw up and it negates the low frequency response your looking for from your current enclosure. In conclusion I think it's a bad idea and will not net the gains you want

 

[Suicide Bobb 5,000+ posts]

So take this here -

Now on the left-most panel, put the PR there. That's what I'm looking to do.

So pretty much it's a 6th order enclosure, but with the inside port being replaced by the PR.

 

[winkychevelle 10+ year member]

Turns the box into a sixth order bandpass which if u read further on the12volt.com website is said to be difficult to calculate, easy to screw up, and not recommended for novice installers. No offense

 

[Suicide Bobb 5,000+ posts]

Turns the box into a sixth order bandpass which if u read further on the12volt.com website is said to be difficult to calculate, easy to screw up, and not recommended for novice installers. No offense

Yeah, I'm DEFINITELY not building any boxes for my subs. I get my best friend to do it for me on teh cheapz. He's very good at what he does, but I don't know if he's ready for 6th order. Here's some pics of his work:

My box for my APX, before the double baffled front panel

 

[winkychevelle 10+ year member]

He's done some nice boxes but like I said these are just hard to design and build. Some people have a knack for them others just screw up horribly. I personally would just stick to the 4th order bandpass.

 

[Brian_smith06 10+ year member]

I want to play with some pr stuff. Supposed to have a pretty nice sound

 

[Suicide Bobb 5,000+ posts]

He's done some nice boxes but like I said these are just hard to design and build. Some people have a knack for them others just screw up horribly. I personally would just stick to the 4th order bandpass.

Oh alright.

What else should I do with the PR's then?

 

[Suicide Bobb 5,000+ posts]

I want to play with some pr stuff. Supposed to have a pretty nice sound

Sealed PR boxes seem to sound better than ported boxes imho. I'm probably gunna get hammered for saying that here though //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

 

[Imtjnotu 5,000+ posts]

I did a lot of looking into pr's befoe I bought a tc oem....they are suppose to be better then ports...no port noise or anything...u get better out put and sq..but if u use a pr ur sub has to be of a smaller size...like a 10" subs needs a 12" pr....u have to double the cone area....slo the pr needs to have almost comparable xmax if I remember....there is no point putting a pr into a pot atleast I think

 

[Suicide Bobb 5,000+ posts]

I did a lot of looking into pr's befoe I bought a tc oem....they are suppose to be better then ports...no port noise or anything...u get better out put and sq..but if u use a pr ur sub has to be of a smaller size...like a 10" subs needs a 12" pr....u have to double the cone area....slo the pr needs to have almost comparable xmax if I remember....there is no point putting a pr into a pot atleast I think

All these things are true.

I'm not sure that you get better output vs. a ported box though. Otherwise, we would be seeing tons of PR's in comps. And the Xmax needs to be around half that of the sub from my experience.

The biggest concern is doubling the cone area. That's why I suggested two 12" PR's with my two 10" subs. I may also do both GTR's with my 12" Eclipse TI. Oddly enough though, Boston recommends the 12" GTR with the 12" G5...not sure what their reasoning is there but I trust them lol.

Btw...Boston sure doesn't cheap out on anything. They sent me an allen wrench to change the weights inside the GTR (to tune it to either 30, 35, or 45hz), but they didn't just send me a standard cheap-o allen wrench. It was a bull-head allen wrench, which generally cost more. I know, we are talking pennies here, but it's the details that count. I was happily surprised to see that they sent a bull-head allen wrench instead of the standard kind.

 

[winkychevelle 10+ year member]

You don't need double the cone area if the Xmax of the pr is the same or more than the driver. Doubling the cone area is done to prevent over excursion of the pr. But if u have the same xmax or more xmax this is unessesary as u shouldnt exceed the limitations of the pr. Reason why Boston recommends using a 12 pr with a 12 sub.