Passive Radiator

[jeremyyakavonis]

Hi, I have a question. I just bought an earthquake SLAPS 12 Passive radiator and of course no specs come with it so I cannot sue bassbox to figure a box to put it in with subwoofer I have chosen. I tried calling up earthquake sound and a technician tells me that passive radiators dont have any specs which bassbox needs, yet every other passive radiator I see for sale such as on partsexpress give all the specs you would need. Anyone have any idea what I should do? Have looked for other websites and reviews hoping to get any info but all show the same information thier main website shows.

[alexb]

Here is some design info. for passive radiators that may be of help.

<A HREF="http://www.diysubwoofers.org/prd/">http://www.diysubwoofers.org/prd/</A>

[Wolf]

The LSDC has a section on testing PR's for the designing IN-BOX. You'd need to first build a box and then test it. Is this the Magma flat-piston PR? Do you have a pic?
Later,
Wolf

[jonpike]

"Passive Radiators don't have paramters" Yeah, right... Guess he used to work at a Fry's? Changed the Plasma one time too many at a boutiqe HT store?

You might look around to see if there's testing info online. Not sure if I've seen any, but I've seen tecniques in the testing books, where you put the passive in a test box, and have a smaller driver pumping it to get the T/S params. A fair amount of extra work, and you need a test setup, but then you'ld accurately have everything you need.

I don't know how far you might get with WinISD alpha, by determining a few things and letting the program calc the rest. Might need more than you could get without that test setup.

Good luck!

[jeremyyakavonis]

> The LSDC has a section on testing PR's for
> the designing IN-BOX. You'd need to first
> build a box and then test it. Is this the
> Magma flat-piston PR? Do you have a pic?
> Later,
> Wolf
Yea it is the PR that is with the magma here is link for the specs that they give on website:

javascript:location='supernova15.htm';window.open( 'slaps.htm','Slaps','height=500,width=800,scrollba rs=yes') If that doesnt work try this link

<A HREF="http://earthquakesound.com/supernova15.htm">http://earthquakesound.com/supernova15.htm</A> then on that page says SLAPS PR click for specs. I sent earthquake another email and maybe they might actually respond back to me but maybe not.

[jeremyyakavonis]

well no answer from my email, so I tried calling earthquake again and got a different person and managed to explain that a passive radiator has its own specs and is not the specs of the subwoofer you use it with and they said theyll email me the specs for it. I just pray and hope that its not the specs that they show on their website.

[Wolf]

> well no answer from my email, so I tried
> calling earthquake again and got a different
> person and managed to explain that a passive
> radiator has its own specs and is not the
> specs of the subwoofer you use it with and
> they said theyll email me the specs for it.
> I just pray and hope that its not the specs
> that they show on their website.

The only way I know to get them is to test for them. PR's are a different bird for sure!
Good luck,
Wolf

[danmarx]

> Here is some design info. for passive
> radiators that may be of help.

> <A HREF="http://www.diysubwoofers.org/prd/">http://www.diysubwoofers.org/prd/</A>

Brian's method is very good, I've used it and can say that it does work. All you really need to know about the PR is the weight and the Sd. You can calculate the Sd by taking the diameter of the PR plus 1/3 of the surround as he describes, and then the weight of the PR in your case will probably be 90% of the total weight of the entire PR, since it's basically one big radiating diaphram. Just weight the whole thing and then figure it's somewhat lighter than that minus the cast frame (which you could also calculate). With those two numbers you can design your box, but you won't be able to tune the box, the weight of the PR defines the tuning which is fixed, (unless you can figure out how to add/remove mass) you're best bet is to determine what the tuning of different sized boxes would be and then pick a driver that best suits it.

[dlr]

> well no answer from my email, so I tried
> calling earthquake again and got a different
> person and managed to explain that a passive
> radiator has its own specs and is not the
> specs of the subwoofer you use it with and
> they said theyll email me the specs for it.
> I just pray and hope that its not the specs
> that they show on their website.

Their specs page indicates a lack of a spider, making the support of all weight entirely dependent on the surround. Their references to other PRs is also based on cheap PRs. It would appear that shallow mounting, due to no inner frame/spider, is a key characteristic. I doubt that this is an issue with any home-use systems.

They need someone to fix the rather sad gramatical error at their site, "...its forward movement inhabits different resistance...".

Absolutely no T/S params available at the site. That alone would direct me elsewhere. If you want a truly top-notch PR, I'd look to Peerless or Seas. They provide all of the information required to design before buying. I also am of the opinion that they are of higher quality and will not suffer from long-term suspension sag that one having only surrounds will exhibit. The admonition against "typical" PRs with a spider may be true of cheap PRs, but the Peerless and Seas units are not going to suffer from this. It does make good ad copy, though.

dlr

[Wolf]

As I recall, there is a spider on this PR. The frame and cone/spider are exactly the same as the active driver, just no magnet structure. There was an article about the Supernova in HT, and they had an 'acrylic' box in addition to the black-ash box version. It was clear the suspensions were the same. It is supposed to be a very nice PR.
Later,
Wolf

[dlr]

It would certainly be good if it had a spider. How is weight added to it?

dlr

[jeremyyakavonis]

> It would certainly be good if it had a
> spider. How is weight added to it?

> dlr

It says there is a 1 inch wide section in the middle between either sides of the surround and they say thats where you add the weight. wish I were able to show pics would be easier to see.

[jrp]

> Hi, I have a question. I just bought an
> earthquake SLAPS 12 Passive radiator and of
> course no specs come with it so I cannot sue
> bassbox to figure a box to put it in with
> subwoofer I have chosen. I tried calling up
> earthquake sound and a technician tells me
> that passive radiators dont have any specs
> which bassbox needs, yet every other passive
> radiator I see for sale such as on
> partsexpress give all the specs you would
> need. Anyone have any idea what I should do?
> Have looked for other websites and reviews
> hoping to get any info but all show the same
> information thier main website shows.

I've tried for years to get a response from EQ or their dealers about the specs for the SLAPS PR's - to no avail. EQ has two different PR's, models that resemble typical PR's and the SLAPS (better) ones that are simple a disc of mdf with two surrounds attached front and back. This stops the cantilever effect inherent to typical PR's and allows for huge excursion (I've measured the peak to peak excursion of the SLAPS 15 to be just under 4 inches.) To add weight, you simply add washers to the bolt that is mounting dead center in the middle of the disc. If anyone can find specs on these, I would pay for them. My projects with them have been simple copies of the EQ Supernova subs - at far lower costs.
JP

[dlr]

> I've tried for years to get a response from
> EQ or their dealers about the specs for the
> SLAPS PR's - to no avail. EQ has two
> different PR's, models that resemble typical
> PR's and the SLAPS (better) ones that are
> simple a disc of mdf with two surrounds
> attached front and back. This stops the
> cantilever effect inherent to typical PR's
> and allows for huge excursion (I've measured
> the peak to peak excursion of the SLAPS 15
> to be just under 4 inches.)

I take this to mean the suspension is only the surround. How is it protected from over-excursion?

> To add weight,
> you simply add washers to the bolt that is
> mounting dead center in the middle of the
> disc.

This scheme appears to be susceptible to suspension sag over time.

dlr

[jeremyyakavonis]

> I've tried for years to get a response from
> EQ or their dealers about the specs for the
> SLAPS PR's - to no avail. EQ has two
> different PR's, models that resemble typical
> PR's and the SLAPS (better) ones that are
> simple a disc of mdf with two surrounds
> attached front and back. This stops the
> cantilever effect inherent to typical PR's
> and allows for huge excursion (I've measured
> the peak to peak excursion of the SLAPS 15
> to be just under 4 inches.) To add weight,
> you simply add washers to the bolt that is
> mounting dead center in the middle of the
> disc. If anyone can find specs on these, I
> would pay for them. My projects with them
> have been simple copies of the EQ Supernova
> subs - at far lower costs.
> JP

Hey JP you say to add weight you add washers to the bolt in the dead center of the middle of the dics?? On my SLAP 12 there is no bolt on either side in the middle. All there is is a 1 inch slot around the entire middle of the driver, so unless they changed its design since you have bought them. I was hoping to make a nice car sub with one of these. So you think it would be easiest to just make a copy of the EQ supernova for my car, If so how much weight did you add to the PR?

[jrp]

> Hey JP you say to add weight you add washers
> to the bolt in the dead center of the middle
> of the dics?? On my SLAP 12 there is no bolt
> on either side in the middle. All there is
> is a 1 inch slot around the entire middle of
> the driver, so unless they changed its
> design since you have bought them. I was
> hoping to make a nice car sub with one of
> these. So you think it would be easiest to
> just make a copy of the EQ supernova for my
> car, If so how much weight did you add to
> the PR?

Do you have the SLAPS, or the traditional 12" PR? The SLAPS is just a disc, and there is a bolt in the middle. I will have to check my measurments, but I believe that it required about 11 ounces to tune the system to 17hz - which is the native tune by EQ.

[jrp]

> I take this to mean the suspension is only
> the surround. How is it protected from
> over-excursion?

> This scheme appears to be susceptible to
> suspension sag over time.

> dlr

There is not traditional suspension, which is actually good in that they limit excursion. The EQ system uses very thick santoprene surrounds that almost certainly have more restoring force than any spider assembly. If you used no, or minimal weight, I see no reason why suspension sag would be a problem with these PR's. There are two reasons why you wouldn't use the SLAPS for horizontal use - 1. PR's should really never be used horizontally. 2. The extreme weight used to tune the SLAPS would lead to severe sag.
JP

[jeremyyakavonis]

> Do you have the SLAPS, or the traditional
> 12" PR? The SLAPS is just a disc, and
> there is a bolt in the middle. I will have
> to check my measurments, but I believe that
> it required about 11 ounces to tune the
> system to 17hz - which is the native tune by
> EQ.

I know I have the SLAPS 12, there is a flat fidc in middle with surrounds on both sides and on the side that faces into the enclosure the surround has holes 1/2" diameter spaced 4 inches apart around the whole inside surround, but there is no bolt in the middle of the disc on either side. All there is, is a 1 inch slot around the speaker where the 2 surrounds meet where the disc is. if that makes sense.

[jeremyyakavonis]

Hey JP I saw a pciture of the SLAP 12 that you are talking about has a bolt on the back of the middle of disc and has square slits around the surround. Mine instead of square slits has holes around and doesnt have that bolt in the middle of disc.