# Your take on Passive Radiators



## number9 (Dec 7, 2007)

I don't know alot about these setups, so I'm wanting to know your opinion on using a PR setup. Pros/cons pics whatever is welcome.


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## chad (Jun 30, 2005)

Cons, needy on space, the PR should be larger than the active driver
BUT if depth is a concern......... and the enclosure is already small and a BIG port would add too much.

Pros, easier to "tune" just add weight or remove weight.

They act much similar to a vented enclosure BUT IIRC there are some tradeoffs or a quirk I can't remember, nothing to break the bank but certainly a bit different.


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## number9 (Dec 7, 2007)

Thanks, I've been trying to understand more of how these work. As well as IB setups. My other car is running again and I am wanting to try something new. Anyone else feel free to chime in.


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## Gearhead51 (Nov 19, 2008)

Like Chad said, they are tuned radiators similar in function and sound to a port, but much more expensive. They are useful when the tuning frequency is lower than would be possible with a port due to enclosure size. They tend to unload the driver under the tuning frequency similar to a port. They are also not subject to chuffing or port noise. Of course, I guess they could make noise when pushed.


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## Fish Chris (Dec 14, 2008)

I had a buddy back in the day who had 4 10"s... all powered (but by two, 2 ch amps) Then he fried one of the amps. We were all totally surprised that with two of the subs not even hooked up, it was "at least" as loud.... but amazingly, sounded even better ! He got the other amp fixed, but stuck it in his closet as a back up  
Pure luck of the draw though, as none of us knew anything about the science of passive radiators..... and I still don't know much.

One thing I think is dumb though.... a PR would HAVE to be cheaper for a company to produce, than a full speaker with motor assembly.... Yet because of their rarity, they make them seem like they are "ooooh ahhhhh special", and charge just as much as if it was a full, powered speaker :-( Dumb.

Peace,
Fish


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## Canadian_Dude (Feb 4, 2009)

I use a pair of 18" PR's in my DIY home sub and love them. They are only $100 each, made with an MDF cone. I definitely want to try PR's in my truck. PR's should be minimum double the displacement of the active driver, so using them 2:1 is common. They are great for when you can't fit a long enough port in the enclosure, they are also nice because you don't lose as much air space in your box as with a port, so the box can be made smaller for the same tune.


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## aznboi3644 (Jan 25, 2009)

Did you make that PR with the MDF cone or you put an MDF cone on it for added weight??


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## FG79 (Jun 30, 2008)

Passive Radiators are great. My home speaker is an 8" woofer with an 8" passive radiator. 

I believe PR's roll off faster than vented enclosures....I think that is there weakness compared to standard vented from a performance point of view. Is harder to tune I believe.

Not that anyone is doing it, but if ever one attempted to do a ported enclosure in a car door....a PR would seem far easier to execute than any type of port.


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## chad (Jun 30, 2005)

FG79 said:


> I believe PR's roll off faster than vented enclosures....I think that is there weakness compared to standard vented from a performance point of view.


THAT'S the weird issue I was trying to remember!


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## Oliver (Jun 25, 2007)

Good read >

HUMAN Speakers: What is a passive radiator?


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## Brian Steele (Jun 1, 2007)

chad said:


> Cons, needy on space, the PR should be larger than the active driver
> BUT if depth is a concern......... and the enclosure is already small and a BIG port would add too much.
> 
> Pros, easier to "tune" just add weight or remove weight.
> ...


They roll off a bit faster than a vented system, and there's a massive null in the response (and a correspondingly BIG shift in group delay) at the PR's resonant frequency, but this null occurs outside of the system's passband anyway. The larger the PR, the lower the resonant frequency (another good reason to use large PRs... ).

An augmented PR system basically eliminates the null (and quite likely the group delay issue as well). However, I've never seen one actually built, much less heard one. It's described in the Dickason's LDC. I suspect cost and complexity is likely why they're hard to find .

See The Subwoofer DIY Page - Passive Radiator Systems for more PR details...


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## Canadian_Dude (Feb 4, 2009)

The cone on my passives was made with MDF, the mms on them is 1600g, it also has it's own suspension as well. PR's can be tuned higher and lower after final construction, and ports don't grow very well. There is also the two impedance spikes, at the active speakers f3, and the PR's f3.

Here is what the PR looks like:
AE Speakers --- Superb Quality, Unforgettable Performance, Definitely.


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## norcalboris (Feb 28, 2009)

my shop just did a 64 impala with the boston SPG555 and the matching passive radiator and i loved the sound of it, Im planning on doing some in my own car


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## HondAudio (Oct 19, 2006)

Is the "Acoustic Lever" anything like this picture?


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## br85 (May 2, 2008)

I can't find ANY info on it now but I remember reading something about the benefits of using 2 matched subs in one sealed enclosure with one of them installed inverted. NO idea why, or whether it was credible, but if you want to try something new, it might be worth giving it a go. I think, as with all dual-driver shared enclosures, the net volume should be double what one driver would require. Bit harder to calculate when one is ass-out.

Oh, and the real downside of course, is that you've gotta buy 2 subs, and it won't look like the prettiest thing ever.


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## Brian Steele (Jun 1, 2007)

HondAudio said:


> Is the "Acoustic Lever" anything like this picture?


Not quite. That's a 4th order BP system with a passive radiator instead of a port.

Turns out the APR I mentioned earlier and the "acoustic lever" are quite similar. 

To imagine what it looks like, take that image above, and add to the front of it another volume with a larger PR, and link both PRs together in some way. As the larger radiator will move in unison with the smaller one, output will be greater because of the larger surface area. Geddes, the inventor, claims it's capable of 6dB (or more) output than the same driver used any other alignment, and better than a bass horn for the same box volume too.


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## Canadian_Dude (Feb 4, 2009)

br85 said:


> I can't find ANY info on it now but I remember reading something about the benefits of using 2 matched subs in one sealed enclosure with one of them installed inverted. NO idea why, or whether it was credible, but if you want to try something new, it might be worth giving it a go. I think, as with all dual-driver shared enclosures, the net volume should be double what one driver would require. Bit harder to calculate when one is ass-out.
> 
> Oh, and the real downside of course, is that you've gotta buy 2 subs, and it won't look like the prettiest thing ever.


I found this information on the subject:



> Compound ~ Push/Pull Dual Drivers
> Basic Theory
> 
> Two drivers share an acoustic volume of air within a single enclosure. The best way to take advantage of this alignment is to mount one driver facing outwards with the other driver inverted and facing inwards. The drivers are then wired so that they are electrically out of phase while remaining mechanically still in phase with one another. Odd ordered harmonics are cancelled out by using this approach according to Vance Dickason. According to M&K who specialize is push/pull subwoofers claim that this approach cancels out even ordered harmonics. So take your pick. Either way, harmonic distortion is reduced in that any anomalies or variations in the two driver's spider, cone or suspension characteristics are canceled out by the other driver's inversely proportional anomalies and variations. The sound is as accurate and pure as it can possibly be with each driver "correcting" the other driver. Of course many times two drivers will share the same acoustic volume of air while maintaining the more traditional look of having both drivers fire forward into the listening environment. Though this does not have the same harmonic cancellation effect, all other characteristics between the two alignments is identical. Box volume must be twice that of a single driver. This can be easily modeled by taking the Vas of a single driver and multiplying it by two. The system has an increased efficiency of 3dB over a single driver. Power handling for the system is twice that of single driver. Frequency response is the same for a single driver in an enclosure excaly half the size.
> ...


Came from here: Audio Innovation - by Dan Marx www.danmarx.org


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## FG79 (Jun 30, 2008)

Canadian_Dude said:


> I found this information on the subject:
> 
> 
> 
> Came from here: Audio Innovation - by Dan Marx www.danmarx.org


Yeah, this is Isobaric loading....

JL Audio

Has its advantages, but I suspect it was more useful back then when enclosures needed to be larger.


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## cubdenno (Nov 10, 2007)

Not sure if everything *has* to be bigger but it is recommended. My old Sunfire home sub had like a 10 inch woof with a 10 inch passive and it literally shook my whole house. And remember those old Stillwater Kicker boxes with the 8 inch woofers the piezo horn tweets and the either single 10 or double 10 inch PR's from the eighties and early nineties?


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## Canadian_Dude (Feb 4, 2009)

FG79 said:


> Yeah, this is Isobaric loading....
> 
> JL Audio
> 
> Has its advantages, but I suspect it was more useful back then when enclosures needed to be larger.


Isobaric requires half the box volume to acheive the same q...


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## HondAudio (Oct 19, 2006)

cubdenno said:


> Not sure if everything *has* to be bigger but it is recommended. My old Sunfire home sub had like a 10 inch woof with a 10 inch passive and it literally shook my whole house. And remember those old Stillwater Kicker boxes with the 8 inch woofers the piezo horn tweets and the either single 10 or double 10 inch PR's from the eighties and early nineties?


I've heard one of those Sunfire subs in a demo room. Amazing. If somebody cloned the idea in a car it would rattle your fillings out. :surprised:


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## W8 a minute (Aug 16, 2007)

cubdenno said:


> And remember those old Stillwater Kicker boxes with the 8 inch woofers the piezo horn tweets and the either single 10 or double 10 inch PR's from the eighties and early nineties?


That was a great sounding box back in it's day. Far from audiophile but when compared to other "boom box" offerings at the time it was far superior.

I also remember a box where two 8's were loaded behind a single 10". The 8's coupled with the 10' in an isobaric fashion. Looking at the box you seen a single 10" but behind it where 2 8's. I never heard it play though.

PR's always fascinated me because I don't understand them. Initially you would think the PR would CANCEL the bass output but obviously it doesn't.


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## FG79 (Jun 30, 2008)

Canadian_Dude said:


> Isobaric requires half the box volume to acheive the same q...


I know...

Just saying that subwoofers of old tended to require larger enclosure volumes in general than they do now. Say 1.0 - 1.5 cubic feet for a 10" compared to about .4 - .7 cubic feet for most 10" subs these days.


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## zwc0442 (Oct 24, 2008)

I've been using a boston g5 with their gtr tunable radiator and really like the way it sounds. Its also requires much less space than the same sub would need for a ported box. My box is 1 cu ft and does really well. I was surprised how loud it can get and still sound good.


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## W8 a minute (Aug 16, 2007)

FG79 said:


> I know...
> 
> Just saying that subwoofers of old tended to require larger enclosure volumes in general than they do now. Say 1.0 - 1.5 cubic feet for a 10" compared to about .4 - .7 cubic feet for most 10" subs these days.


I've found a lot of these new subs still perform better in a larger enclosure. I think some companies list a smaller box size just to entice people to buy.


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## cubdenno (Nov 10, 2007)

FG79 said:


> I know...
> 
> Just saying that subwoofers of old tended to require larger enclosure volumes in general than they do now. Say 1.0 - 1.5 cubic feet for a 10" compared to about .4 - .7 cubic feet for most 10" subs these days.


a lot of the volume spec is related to power handling. With the advent of these 1000 watt + amps for a hundred bucks, the woof manufacturers list small enclosures which increase power handling. So less warranty replacement. Some of the free modeling software for enclosures such as winisd and unibox to name a couple can show what you can get mathematically with the woofer/box combo. Play around and see what you can get with different box sizes.


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## FG79 (Jun 30, 2008)

W8 a minute said:


> I've found a lot of these new subs still perform better in a larger enclosure. I think some companies list a smaller box size just to entice people to buy.


I agree completely. 

Look at old JL specs....they recommend a 2.5 cubic foot ported enclosure for the 10W2 and 3.5 cubic feet for the 12W2. 

They recommend 1.5 cubic feet vented enclosure for the present day 12w6v2. 

Say what you want about T/S parameters, that's quite a big difference in enclosure size for a 12" driver.


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## orangelss (Dec 20, 2008)

W8 a minute said:


> That was a great sounding box back in it's day. Far from audiophile but when compared to other "boom box" offerings at the time it was far superior.
> 
> I also remember a box where two 8's were loaded behind a single 10". The 8's coupled with the 10' in an isobaric fashion. Looking at the box you seen a single 10" but behind it where 2 8's. I never heard it play though.
> 
> PR's always fascinated me because I don't understand them. Initially you would think the PR would CANCEL the bass output but obviously it doesn't.


Think your talking about the old Blues ISObox system. They sounded pretty good. They also made a drop in ISO kit. Company was always willing to try something new.


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## HondAudio (Oct 19, 2006)

Did JL Audio ever make a passive radiator?


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## kinchu007 (Apr 5, 2008)

I'm not a fan. Sealed for dance music, ported for hip hop (using an MDF wall, not a PVC port -- less port noise).


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## cubdenno (Nov 10, 2007)

HondAudio said:


> Did JL Audio ever make a passive radiator?


Not that I ever saw. Dayton has a couple now. Decent "XMAX"



kinchu007 said:


> I'm not a fan. Sealed for dance music, ported for hip hop (using an MDF wall, not a PVC port -- less port noise).


Port noise occurs when the port area is to small. Makes no difference what shape the port is. Slot porting is just easier to figure and manipulate. And a passive is mostly identical to a port. to get ported low it takes a lot of volume and overall box size. The passive lets you go low in a small box because to lower the tuning frequency you add weight/mass to the PR.

Anymore, I will take ported over sealed. You get much lower extension in a properly designed ported enclosure. And generally more efficient as well.


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## chad (Jun 30, 2005)

kinchu007 said:


> I'm not a fan. Sealed for dance music, ported for hip hop (using an MDF wall, not a PVC port -- less port noise).


Epic fail


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## aznboi3644 (Jan 25, 2009)

chad said:


> Epic fail


motion seconded


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## SUX 2BU (Oct 27, 2008)

orangelss said:


> Think your talking about the old Blues ISObox system. They sounded pretty good. They also made a drop in ISO kit. Company was always willing to try something new.


The Blues system was cool. It had a clear acrylic tube with a 10 at each end, facing the same way. The tube was just large enough to hold the front driver without the rear driving hitting it. Does anybody have one of these or ever heard one? I think they called it the "Tri-sobarik" system. Or I'm thinking of just the drop-in kit anyway. I don't recall them using a PR system. I have a pair of Blues 10's I'm running in my commuter car right now actually.

That setup with the two 8s and 1 10 PR in a box that only the PR was visibile, I recall seeing a diagram as well. To my recollection, it was a home theatre sub setup that had two small drivers in a bandpass setup but instead of the front chamber being ported, it used a passive radiator. Not all that unlike what Hondaudio posted up as being a possible Audio Lever diagram.

I agree with FG79 about that other setup which was described using the two drivers, one inverted, sharing the same air space. Sounds just like an isobarik setup to me (similar to the one I just described that Blues made) or a clamshell setup like most isobariks used to be. And yes, the advantage there was 1/2 the box displacement at the expense of two drivers that were connected to amplifier power and I believe 3 dB less sensitivity.


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## Infinity (Jun 28, 2005)

chad said:


> Epic fail





aznboi3644 said:


> motion seconded


I also notice he stopped after 50 posts. Is number 51 in the classifieds?


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## chad (Jun 30, 2005)

auto dupe


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## chad (Jun 30, 2005)

big brain!

http://www.diymobileaudio.com/forum...o-cl-69x-lightly-used-6x9-set.html#post688138

"by nines!"


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## 808Pants (Aug 27, 2009)

*Do passive radiators blow, too?*

my required virgin post to an existing thread...not to hijack, but this is already a pretty old thread:

Do passive radiators blow, too? In my case, checking into the awful blatting bass from my PC's subwoofer (one driver, one PR), I noticed that the "blown" sound seems to be emanating from the PR, and NOT the driver. Removing the PR or damping with fingers removes all trace of the 'blown' sound...but then again, that obviously radically changes the rest of the parameters and the sound in general, so it's not a great test. Now that I have the PR out, I can see that the surrounds look ripply and irregular, though there aren't actual holes in them, it seems a bit limp. 

Is it worth replacing the PR, or is the whole subwoofer ready for the landfill?

--Dave


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## subwoofery (Nov 9, 2008)

I'm planning on using 1 x 15"PR with my 2 x Audiopulse Epic 8" and was wondering if it was possible to tune the PR below the FS of the actual woofer? 
FS of woofer is 30hz 

My question is: Is it to tune the PR below the FS of the actual woofer? Let's say 28hz or even 25hz 
This will "eliminate" the problem associated with PRs (steep roll-off) 

Kelvin 

PS: I have no subsonic filter but can EQ down below tuning...


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## subwoofery (Nov 9, 2008)

Bump


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## Austin (Mar 12, 2009)

*Re: Do passive radiators blow, too?*



808Pants said:


> my required virgin post to an existing thread...not to hijack, but this is already a pretty old thread:
> 
> Do passive radiators blow, too? In my case, checking into the awful blatting bass from my PC's subwoofer (one driver, one PR), I noticed that the "blown" sound seems to be emanating from the PR, and NOT the driver. Removing the PR or damping with fingers removes all trace of the 'blown' sound...but then again, that obviously radically changes the rest of the parameters and the sound in general, so it's not a great test. Now that I have the PR out, I can see that the surrounds look ripply and irregular, though there aren't actual holes in them, it seems a bit limp.
> 
> ...



Sounds like maybe the suspension on it is going out..or something. Not sure. I would try replacing it. Look on partsexpress.com for a new one. They arent too much. I got two 12" passives for about $27 each from there.


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## rugdnit (Dec 24, 2007)

Good reading.... i have two TC OEM PR10's that i am sitting on and waiting to try out on my next install. with that high roll surround they have a ton of throw. i was trying to track down the 12" version to run with my IDMAX, but i was only able to find the 10s. from what i read on the TCs you could run 1 to 1, so i am figuring that 2 10" PRs will be sufficient for a 12. i will give it a go-- and will pass on the results when i finally get to it.


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## ou812 (Oct 25, 2008)

Nothing for me to add on the tech side like you guys nut I have a pair of Polks with a pr and they sound incredible.














Like I said nothing really to add.....move along.


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## subwoofery (Nov 9, 2008)

subwoofery said:


> I'm planning on using 1 x 15"PR with my 2 x Audiopulse Epic 8" and was wondering if it was possible to tune the PR below the FS of the actual woofer?
> FS of woofer is 30hz
> 
> My question is: Is it to tune the PR below the FS of the actual woofer? Let's say 28hz or even 25hz
> ...


Anyone?


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## Austin (Mar 12, 2009)

Heres my home theater sub:

One 12" memphis with two 12" dayton passives. Rocks the house for sure with only 170 watts.


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## chad (Jun 30, 2005)

subwoofery said:


> I'm planning on using 1 x 15"PR with my 2 x Audiopulse Epic 8" and was wondering if it was possible to tune the PR below the FS of the actual woofer?
> FS of woofer is 30hz
> 
> My question is: Is it to tune the PR below the FS of the actual woofer? Let's say 28hz or even 25hz
> ...


It will be nearly like venting it below the Fs.. model that and see what it will do.

A PR acts as a vent in that it's a resonating device. You tune a pipe by length and a resonating body by weight.

As for the quirks between the two.. I would not worry about it.


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