Stereo Integrity HS24 Passive Radiators - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 23 Old 03-19-2019, 04:53 PM - Thread Starter
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Stereo Integrity HS24 Passive Radiators

I noticed that Nick has a photo of a new Passive Radiator for the HS24 on facebook.

I’m curious on how a passive radiator would perform with one HS24 driver in a 10cuft enclosure?

Passive Radiator specs to plug into WinISD?

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post #2 of 23 Old 03-19-2019, 05:02 PM
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That’s cool, think two pr minimum per hs24. I hope less than 10 feet but at that volume probably very loud
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post #3 of 23 Old 03-19-2019, 08:51 PM
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Those suckers have to be expensive. Can't image the cubic foot savings/output increase would be worth the cost. Could probably build two 21's for same price.
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post #4 of 23 Old 03-20-2019, 01:15 AM
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Those suckers have to be expensive. Can't image the cubic foot savings/output increase would be worth the cost. Could probably build two 21's for same price.
You'd get a much shallower drop off post tuning and with a 24, the port would most likely be quite massive. Still this would cost a lot, I wonder what the bigger benefits would be versus building a horn and keeping nearfield subs for ULF.
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post #5 of 23 Old 03-20-2019, 01:22 AM
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Is there a price stated for the PR's?

If your trying to tune your 24 low you are going to have to use EQ if wanting the volume to be kept small.(10cuft) Would be like the VBSS design but obviously bigger. I had always thought about a 6th order design using a 21"with a 24"PR. Sort of like Seaton did with a design a while back. Was a different smaller driver but the alignment was interesting. But shipping killed most of my ideas. Either way happy to see Nick has these as an option.
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post #6 of 23 Old 03-20-2019, 03:40 AM
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That is very cool. Iwas joking around about some Hs-24 passive radiators a few months ago. Nick must have heard my thoughts. I do think you would need 2 to make it work. If you put them all on the front you would end up in the 20cf range quite quickly and i would bet that is where they are going to shine. I don't know how to model anything right now but i bet someone could tell us if it is a good idea or not. Ido wonder on the price range of them.
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post #7 of 23 Old 03-20-2019, 05:28 AM
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Glad to see these, options are few for high excursion passive radiators.

Are these *based* on the HS-24 soft parts, or are they smaller diameter *for* use with the HS-24?

Looks like there's no provision to change the mass from the front? I'm assuming there's an easy way to at least change the mass from the rear?

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post #8 of 23 Old 03-20-2019, 06:52 AM
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Wonder if a single 24" passive would be enough if you were using a 18" or 15" active driver in conjunction.......... I think normally you want your passive to have 2x the surface area of the active driver, but I suck at math so I could be very off lol.....

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post #9 of 23 Old 03-20-2019, 06:57 AM
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Typically the PR is at least double and if I was building one I would put the two PR on the sides to cancel at least their forces. The old strike 15 used two 18” PR probably because the woofer had more excursion capability than the PR but they had pretty beefy surrounds too so I’m not sure. But definitely two PR minimum. If the PR has the same surround as the hs24 that is probably enough but those things will be a flappin at tuning.
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post #10 of 23 Old 03-20-2019, 07:19 AM
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Originally Posted by Vince_B View Post
Typically the PR is at least double and if I was building one I would put the two PR on the sides to cancel at least their forces. The old strike 15 used two 18” PR probably because the woofer had more excursion capability than the PR but they had pretty beefy surrounds too so I’m not sure. But definitely two PR minimum. If the PR has the same surround as the hs24 that is probably enough but those things will be a flappin at tuning.

Maybe i am miss thinking here but if all were on the same plane you wo be no worse off than if just the active driver. Wouldn't the mass cancel each other out because as one goes out the other goes in. That was my thought at least. Would sure look cool to have either 2 stacks of 3 cones or 6 across the bottom of the screen. It will be interesting to find out more about these
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post #11 of 23 Old 03-20-2019, 07:26 AM
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Originally Posted by Randy_J View Post
Maybe i am miss thinking here but if all were on the same plane you wo be no worse off than if just the active driver. Wouldn't the mass cancel each other out because as one goes out the other goes in. That was my thought at least. Would sure look cool to have either 2 stacks of 3 cones or 6 across the bottom of the screen. It will be interesting to find out more about these

I think what will actually happen around tuning is the active driver will move a small amount and the two very massive PR cones will move a lot. You can sim it to see what mass will be needed on the PRs but it will be a lot. The old stryke PRs 18” times two had a slab of 3/4” mdf as the diaphragm for example.
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post #12 of 23 Old 03-20-2019, 10:11 AM
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Quote:
Originally Posted by Randy_J View Post
Maybe i am miss thinking here but if all were on the same plane you wo be no worse off than if just the active driver. Wouldn't the mass cancel each other out because as one goes out the other goes in. That was my thought at least. Would sure look cool to have either 2 stacks of 3 cones or 6 across the bottom of the screen. It will be interesting to find out more about these


Think of them as ports. If you want a lower tune you have to account for a larger driver. Having two PR’s is similar to having a dual vented port.

I don’t know the TS on these PR’s, I’d take a stab at modeling them.


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post #13 of 23 Old 03-20-2019, 10:22 AM - Thread Starter
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This is my double 24 sealed box. I have two made expecting to do 4 drivers, now im wondering if I can do one PR and one active in each 20CF cab, and what that would bring me for performance. Its 20cf net.

I also considered taking the second driver opening, making a plug that mounts like a driver, sealed in the opening, and has ports for a low tune in it. I have 2 drivers and was going to order the other two shortly but now Im thinking of a PR or the low ported box with just the two.


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post #14 of 23 Old 03-20-2019, 10:41 AM
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Originally Posted by FOHTech View Post


This is my double 24 sealed box. I have two made expecting to do 4 drivers, now im wondering if I can do one PR and one active in each 20CF cab, and what that would bring me for performance. Its 20cf net.

I also considered taking the second driver opening, making a plug that mounts like a driver, sealed in the opening, and has ports for a low tune in it. I have 2 drivers and was going to order the other two shortly but now Im thinking of a PR or the low ported box with just the two.


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Man that is a nice looking box there. Please tell me you had that all cnc cut. Otherwise i am just going to feel bad about my abilities
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post #15 of 23 Old 03-20-2019, 11:12 AM
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I wondered when Nick was going to have some ready....

I wonder if we will see some builds with them???
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post #16 of 23 Old 03-20-2019, 11:39 AM - Thread Starter
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Ill give him a shout and report back...


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post #17 of 23 Old 03-20-2019, 01:25 PM
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Man that is a nice looking box there. Please tell me you had that all cnc cut. Otherwise i am just going to feel bad about my abilities
All you need is a router circle guide! Lots of quality woodworking done before computers!!

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post #18 of 23 Old 03-21-2019, 06:44 AM
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Think of them as ports. If you want a lower tune you have to account for a larger driver. Having two PR’s is similar to having a dual vented port.

I don’t know the TS on these PR’s, I’d take a stab at modeling them.


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It's the opposite with PR's. Adding two raises the tuning freq in which case you have to add mass to both to lower it again.

As for a sub and a PR on the same side the cabinet will walk in a circle, I've done it.....
Single PR's of the same size as the sub in the opposed position work well but cab volume needs to be considered. Going smaller (normal recommended sealed size) is better for the PR to make the most out of the drivers excursion and the PR's.
Give them enough juice and they will walk around also though like the wind up walking teeth.
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post #19 of 23 Old 03-22-2019, 12:27 AM
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It's the opposite with PR's. Adding two raises the tuning freq in which case you have to add mass to both to lower it again.

As for a sub and a PR on the same side the cabinet will walk in a circle, I've done it.....
Single PR's of the same size as the sub in the opposed position work well but cab volume needs to be considered. Going smaller (normal recommended sealed size) is better for the PR to make the most out of the drivers excursion and the PR's.
Give them enough juice and they will walk around also though like the wind up walking teeth.
Adding two ports also raises the tuning frequency. Internal cab volume as always affects the tuning of either the PR or the port (and sealed Fb). The two are comparable in many ways but never the same. Jeff Bagby wrote a pretty cool excerpt about PR's and his journey when designing a tower with PR's down to 20hz.


I don't think I'd recommend single PR either.
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post #20 of 23 Old 03-22-2019, 08:09 AM
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The ported speaker behaves like a mass/spring system. The air inside the box is the spring, the air in the port is the mass and the forcing function is the driver. At resonance the driver and the mass of air are moving in opposite directions (when mounted on the same side they are moving in the same direction, but both moving away from the box at the same time).

The 'apparent' mass in the port increases when the port gets longer or smaller in diameter. When the mass goes up the resonant frequency goes down. When you as an extra port the air goes in and out more easy, right? So the resonant frequency goes up in that case.

I tell everyone to get yourself a rubber band and a little weight. While hanging the weight move you hand up and down slowly. The weight and your hand are in phase. As you speed you hand up you will get to the point where the weight is really moving up and down with a lot of displacement and you'll also notice that your hand is going up while the weight is going down -- this is the resonant frequency. As you continue to increase the frequency of your hand (input frequency) at some point your hand is going up and down rapidly but there weight doesn't respond. This is why a driver falls off on the top end -- the driver can't respond to the high frequency being input.

A ported box behaves exactly like that. It's fun try it, then amaze your friends! With the same rubber band you can try something that weighs more and the resonant frequency drops. Less mass it goes up.

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post #21 of 23 Old 03-22-2019, 09:51 AM
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I love the rubber band explanation... simple, eloquent, and easily understood/replicated...
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post #22 of 23 Old 03-22-2019, 10:58 PM
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Originally Posted by Trimlock View Post
Adding two ports also raises the tuning frequency. Internal cab volume as always affects the tuning of either the PR or the port (and sealed Fb). The two are comparable in many ways but never the same. Jeff Bagby wrote a pretty cool excerpt about PR's and his journey when designing a tower with PR's down to 20hz.


I don't think I'd recommend single PR either.
I modeled mine around the Earthquake Supernova series of subs as from my car audio days I still have three of the original (1998) Earthquake Magma's in 12". I bought their PR's (called SLAPS) to go with them.
Funnily enough the Sunfire brand (True sub series) had this design also (was probably the original manufactured version of this arrangement) with virtually identical surround and cones but can't confirm the basket and magnet being the same.....
The only other manufacturer of PR sub designs that I knew of was Definitive Technology with the Supercube which uses a dual PR arrangement and works well.

I ended up using those cheap half inch thick NBR gym mats under them and it works brilliantly regardless of how much excursion they don't budge.
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post #23 of 23 Old 03-23-2019, 01:31 AM
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I modeled mine around the Earthquake Supernova series of subs as from my car audio days I still have three of the original (1998) Earthquake Magma's in 12". I bought their PR's (called SLAPS) to go with them.
Funnily enough the Sunfire brand (True sub series) had this design also (was probably the original manufactured version of this arrangement) with virtually identical surround and cones but can't confirm the basket and magnet being the same.....
The only other manufacturer of PR sub designs that I knew of was Definitive Technology with the Supercube which uses a dual PR arrangement and works well.

I ended up using those cheap half inch thick NBR gym mats under them and it works brilliantly regardless of how much excursion they don't budge.
I think its mostly due to PR's price and the benefits not always justifying the price. I know OEM's will make custom PR's for their own needs, like Klipsch. Salk, etc. There are a few for sale in the DIY market still, like Dayton and I think Eminence with full published TS. I remember those Earthquakes, the marketing for them was hilarious but they were still potent.






I used a bathroom matt in my friends house on their hardwood floor. It was thin and had the tacky underside which prevented sliding on tile. Worked well, but it was only a plain sealed sub, not something that was taking a beating from all sides
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