WinISD Passive Radiator modeling - help plz! - Home Theater Forum and Systems -

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post #1 of 14 Old 08-30-10, 05:23 AM Thread Starter
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WinISD Passive Radiator modeling - help plz!

"Long time listener first time caller"

Hi all, I really hope you guys can point me in the right direction.

For some time now I have been modeling various configurations in WinISD and just can't get the feel for all the variables involved with PRs. All kinds of ported models work out just fine and actually look more promising then PRs.

I'm modeling around AudioPulse AXIS12 QVC with a pair of Exodus PR-15s, and a TC Sounds 3000 (Axis?) QVC with a pair of Exodus PR-18s.

Both VCs are flat-aluminum wind. I do have a sheet for the AP12 but I haven't measured the TC3000 with WT3 to get exact values since what I'm getting from WinISD so far is gibberish anyway.

Here's what I'm not getting. In the PR window I do make sure to select 2 PRs, but what I don't get is the relationship between box volume, added mass on PRs, system power impute and excursions of the driver/PR cones.

I set the power impute at 2500w even though I know I won't get close to that with the EP2500 which I'll be using for the TC3000.

When I try to find a balance between enclosure volume and PRs added mass I keep getting stuck - either drivers cone xmas maxes out or PRs.

I have seen AP12 max out a pair or 15s PR but I though that with 35mm xmas Exodus PRs will be more then enough for 20Hz tuning, but it's just not happening in my models regardless of how much I play with volume/mass.

Initially I decided to go with PRs because as much as I would like to go sonotube route I don't have the skills/space for it. Ported boxes will be a bit of a gamble with these drivers and I prefer the tight sound of a sealed box. Naturally if I could I would have went infinite baffle with as many 18s as I could get but that's simply not a possibility in this house.

Right now I'm running a Dayton 15HO in a sealed box, and even though the box is small for the driver to me it sounds cleaner then ported boxes.

So I'm a bit stuck. As far as building I want to stay away from MDF and would like to try birch on aluminum framing.

I'd appreciate any suggestions!

edit: i should have posted this in DIY section, plz move if possible, thank you.

Last edited by zarus; 08-30-10 at 05:37 AM. Reason: DIY section
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post #2 of 14 Old 08-30-10, 06:09 AM
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Re: WinISD Passive Radiator modeling - help plz!

Thread moved to DIY Subwoofers.

Two Exodus Audio 15" PR's with 1000 grams of mass added to each will tune a 4 cu.ft. box to 20 hz. 1300 watts of power will take the PR's to Xmax at 15.5 hz and the driver slightly above Xmax at 13.5 hz if you use a Hi-Pass filter at 13 hz. That's the best you can do with these PR's and driver combination.

Here's the project file for the TC 3000.

Voland TC 3000.wpr
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post #3 of 14 Old 08-30-10, 10:40 PM Thread Starter
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Re: WinISD Passive Radiator modeling - help plz!

Thank you for the model Mike P.

Your model of one TC300 with a pair of 15" PRs looks better then any of my variations.

I took a look at your file and tried modeling on its bases - I'm still not getting how the tuning freq. is set by all the variables.

In my models I have to increase box volume and add a whole lot of mass to PRs to get the extension.

How you tuned 19.94 in a 4cf box with 1kg of mass i have no idea, and i spent time playing around with mass/filters etc. When I directly copied your values it modeled perfectly, but when I try different combination I end up with a mess.

What I'm shooting for is one 12" AP with a pair of 15" PRs in one box, and one 15" TC3000 with two 18" PRs in another. Two subs total but for different rooms.

I've read and re-read tutorials but I always seem to get with high tuning frequency (23Hz+), large box (5-7cf) and all the way up to 1400 grams of mass.

I noticed that the power is set 1300W, I take it it's the measured output of EP2500 for the 5.6 Ohm of the AP/TC coils. I looked at the coils of both subs and the look identical.

I'll fiddle around some more but honestly I'm just not grasping the relationship between all these variables, and before I get to actual enclosure designing stage I want to set the internal volume as close as possible.
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post #4 of 14 Old 08-31-10, 01:02 AM
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Re: WinISD Passive Radiator modeling - help plz!

Passive Radiator Math

tuning frequency =Fp*sqrt((X*Vap)/Vb-1)

Fp= Passive Radiators Fs
If you add mass you need to run this equation to get the new Fp
Fp = 1/(2(3.14159265)*sqrt((Mms + added Mass) * Cms))

X= Number of PRs
Vap= Total Vas of all PRs added together
Vb= Enclosure Area

Most PR spec sheets will give you Cms. If not... Cms=Vas/(1.2*(343)^2*(Sd)^2)
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post #5 of 14 Old 08-31-10, 03:33 AM Thread Starter
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Re: WinISD Passive Radiator modeling - help plz!

Thank you!

Now i'll be going over all this;

fs= 1/(2(3.14)*sqrt(mms * Cms))
Rms= ((2*3.14)*Fs*Mms)/Qms
Cms = 1 / (2pi*fs)^2 * Mmd
Fp = 1/(2(3.14159265)*sqrt((Mms + Mass) * Cms))
Fb=Fp*SQRT((Num PR*PRvas)/(box volume-1))
Fp= 1/((2*3.14159265)*SQRT((Mms+Mass) * Cms))
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post #6 of 14 Old 08-31-10, 05:39 AM
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Re: WinISD Passive Radiator modeling - help plz!

How you tuned 19.94 in a 4cf box with 1kg of mass i have no idea
For home theater subs there's a optimum box size and tuning frequency for every driver. In WinISD you adjust the box volume and tuning frequency so the sub produces the most low end output while staying within the capabilities of the sub and PR's.

I'll have a look at the files you uploaded after I fly home from work.
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post #7 of 14 Old 08-31-10, 06:16 AM Thread Starter
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Re: WinISD Passive Radiator modeling - help plz!

Well this is puzzling.

I started with 12" Axis Quad, but the ts parameters are different between WinISD profile file, birth sheet and WT3 data I just measured.

WT3 measured (after break in);

Re = 4.88 Ohms
Fs = 27Hz
Qts = 0.382
Qes = 0.419
Qms = 4.366
Le = 2.372
Mms = 200.9 gr
Vas = 2.1 ft^3

Birth sheet;

Re = 4.9 Ohms
Fs = 25.94Hz
Qts = 0.322
Qes = 0.345
Qms = 4.776
Mms = 284.3
Vas= 1.58 ft^3

WinISD profile;

Re = 4.9 Ohms
Fs = 25.70Hz
Qts = 0.345
Qes = 0.367
Qms =5.607
Mms = ?
Vas= 1.57 ft^3

TC3000 WT3 data;

Re = 4.95 Ohms
Fs = 25Hz
Qts = 0.3872
Qes = 0.4192
Qms = 5.051
Le = 2.89
Mms = 272gr (260g?r)
Vas = 5.1 ft^3 (6?)

TC3000 WinISD profile;

Re = 4.630 Ohms
Fs = 22.02Hz
Qts = 0.309
Qes = 0.325
Qms = 6.100
Mms = ?
Vas = 4.556 ft^3

I did disable wi-fi/lan and all unnecessary apps, properly calibrated the device and took multiple measurements to confirm results. For Vas I used added mass method at 229 grams. Any less would not measure.

Any ideas why WT3 test differs so much especially mms, and which ts should i go with?

Thank you much!
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post #8 of 14 Old 08-31-10, 11:07 AM
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Re: WinISD Passive Radiator modeling - help plz!

Go by the birth specs. The other differences besides the mms will result in very minor differences in modeling. I'd trust TC's mms data. I had a WT3 for awhile and it always generated strange mms data. I had tested 4 of the same kind of 18" driver before and got mms readings that varied by more than 100g which is simply not right. Sometimes it would change it for the same driver even. The other parameter that ties in closely with the mms is CMS. The 2 comprise the FS which is what the WFT3 is measuring.
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post #9 of 14 Old 08-31-10, 04:18 PM
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Re: WinISD Passive Radiator modeling - help plz!

Regarding the project files you uploaded, everything appears correct.
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post #10 of 14 Old 09-01-10, 04:01 AM Thread Starter
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Re: WinISD Passive Radiator modeling - help plz!

Thank you very much everybody!

I'm a complete novice and really appreciate the impute.

With these drivers I don't want to just slap a box together and watch them wag. I'd like to understand the theory to the best of my abilities and naturally get the most out of the drivers.

I've read various archived threads of TC DIY projects on this forum, and noticed that there is a considerable difference between generations of TC/AP drivers.

Putting aside measured output of the EP2500, and considering sealed PR enclosure what is the realistic RMS of my VCs? I'll take some pics tomorrow and post them.

I'm curious because in WinISD impute power directly effects all other parameters but modeling is one thing, while real world results often tend to vary a great deal.

If my AP/TC coil can realistically take 2500RMS in a PR enclosure, how much xmas headroom is required for peak power and not RMS? I'd like to understand how it effects peak SPL at xmas.

In my model the smaller 4ft^3 enclosure with a 12" is only 2db lower at 20Hz then a 15" in a 6ft^3 at same 1300W impute, but at peak SPL 12" reaches 118dB at 22.5Hz, while 15" is at 116.5dB, so it's the exact reverse of the SPL graph.

That does not make any sense to me, I expected a considerably higher output from the larger box/cones of the 15/18 combo. I will EQ everything when the time comes, but at this stage I'd like to understand what the real headroom is of the entire combination, and where the linear limits really are. Deep, clean, dynamic bass is a lot more important to me then dB/SPL, and the sound of a bottoming, maxed out driver makes me flat out disappointed

While I am enjoying the learning process I would appreciate if you guys could model your versions of these combos, 12/15 and 15/18 based on EP2500/4000, and models of theoretical max power/physical limits of drivers/PRs with out limitations of the enclosure volume. I'd like to study and compare them all. Also 1400 grams of added mass on the 15 makes me uneasy - seems like a lot of weight to move.

Other aspects which I'm not aware of is how the physical shape of the enclosure will effect the PRs - does the enclosure has to be an even cube in order to balance pressure/group delay or can it be built up? I'm curious because I've seen a vid of a very large box with a forward firing 15" TC3000 with a forward facing 18" PR right on top of it - such arrangement obviously did not work and it was apparent even on the low rez vid.

TC3000 was clearly killing the PR, and even though I'm not sure if running two forward facing cones out of phase has any negative effects below 100Hz, I'm curious if a down firing driver with side firing PRs could be valid in a tower type enclosure rather then a cube.

My desired result is 70Hz to 16-20Hz, no limits on enclosure volume and naturally I'd like to see what the max clean output can be, but since I have a lot to learn so far I'm not able to model properly.

I'll keep fiddling around but looking forward to suggestions!
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