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wattz 20th April 2005 03:31 AM

Switching car audio enclosure to home enclosure
Hey guys,

I just sold my car and now I have my dual 12" subwoofer box with no place to put it in. So now I hooked it up at home and obviously the box wasn't designed for home use. The box is a dual ported 1.75 cu foot per driver using 2 Infinity Kappa Perfect 12D VQ dual voice coil subwoofers. These drivers are rated at 400W RMS/1600W peak!

So what I really want to do is redesign a ported enclosure using both subwoofers. Preferably facing outward (too nice to be hidden) and stacked vertically. Placement of the box will be in the basement, against the wall in the middle with approximately 6.5' space on each side. Any tips on how to design this? eg port size, dimensions, stuffing materials. I'm also using a QSC RMX 2450 amplifier powering it at 2 ohms with 1200W output. Gotta be careful tho.. this amp could blow them at full power.

I know what you're thinking... These are car audio subwoofers and they aren't designed for home use. However, I'm stuck with them now and there's no use selling them for the right kind of drivers. Not to mention, these subs can be dangerous for your health :P If anyone could help me it would be greatly appreciated.

richie00boy 20th April 2005 08:09 AM

Car audio subwoofers can be fine for home use. We need the Thiele-Small parameters of them before we can tell you anything though, especially if you want to go vented.

simon5 20th April 2005 09:52 AM

Perfect12d VQ
Diameter 12" (300mm)
Sensitivity @ 2.83V/1m 92dB
Power Handling 400W RMS/1600W Peak
Frequency Response 23Hz 400Hz
Impedance per voice coil 4 ohms
Voice-Coil Diameter 3" (77mm)
Mounting Depth 7" (178mm)
Overall Diameter 12-3/8" (315mm)
Cut-Out Diameter 10-7/8" (277mm)
Basket Displacement .108 ft^3 (3.06 L)
Voice-Coil DC Resistance Revc 1.66 ohms
Voice-Coil Inductance Levc .81mH
Driver Radiating Area Sd .441 ft2 (.0491M^2)
Motor Force Factor BL w/LowQ Insert 11.86
w/MidQ Insert 9.6
w/No Insert 8.28
Compliance Volume Vas 3.31 ft3 (94.28 L)
Suspension Compliance Cmd 275.39uM/N
Moving Mass, Air Load Mms 189.8g
Moving Mass, Diaphragm Mmd 183.54g
Free-Air Resonance Fs 22.01Hz
Mechanical Q Qms 10.52
Electrical Q Qes w/LowQ Insert .31
w/MidQ Insert .47
w/No Insert .64
Total Q Qts w/LowQ Insert .30
w/MidQ Insert .46
w/No Insert .60
Magnetic-Gap Height Hag 3/8" (10mm)
Voice-Coil Height Hvc 1-11/16" (43.5mm)
Maximum One-Way Linear Excursion Xmax 11/16" (16.75mm)

richie00boy 20th April 2005 10:10 AM

Intertesting. Seems like there's quite a few possibilities with the choice of Qts. You will need the low Q option if you want to use a vented box. What kind of sound and SPL are you looking for?

wattz 24th April 2005 10:41 PM

Problem creating WinISD profile for Infinity Perfect 12D VQ
Ok, I tried inputting the manufacturer's Thiele-Small parameters. However, several ones are missing including:

Rms _____ Ns/m
Dd ______ in
fLe ______ Hz
kLe _______H*sqrt
Vd _______ in^3
Xlm _______ in
Pe _______ w
no _______ %
Znom_______ ohm
USPL_______ dB
SPL ________ dB

Also advanced parameters were missing. WinISD won't let me save it b/c there are parameter errors. If someone knows the missing values or has an Infinity Perfect 12D VQ driver file then please help. Pretty pleeeease :D

Thanks in advance

simon5 25th April 2005 12:34 AM

If you use WinISD Pro, you need to check the "autocalculate parameters" box.

You need to enter the parameters in the order stated in the help file. WinISD Pro will calculate the missing parameters if you entered enough parameters.

Pe is the maximum power in W RMS, so you enter 400.
WinISD will be able to calculate the rest. Some parameters aren't needed for simulation, they are there only for reference.

wattz 26th April 2005 06:04 AM

After messing around with these #'s for 3 hours, I finally got winISD Pro to work it. It was really difficult to get these values closest to the Mfg. spec. I created 2 files for LOW-Q & MID-Q. Could someone check these out and see if they're ok?

It seems that winISD shows that the MID-Q option gives a lower roll off and higher SPL. Maybe I'm just reading the graphs wrong b/c I thought having a higher magnetic flux (LOW-Q insert is larger) would output higher levels at lower frequencies. In other words.. the bigger the better.

simon5 26th April 2005 07:40 AM

Usually, as you can see, the parameters given by the manufacturer are not perfect.

Usually, small variations are not important. The important parameters are Qts, Vas, Fs, Xmax, Re, Le, Pe and Sd. So, even big variations on other parameters are not that important. It takes quite a big variation on Qms to change Qts significantly.

It's better when the manufacturer give accurate specs, but you can do quite a good simulation if important parameters are off by less than 10%.

You did your work very well, the sheets are perfectly good.
You only exagerated Xmax a bit.
If you enter Hg = 10 mm and Hc = 43,5 mm you'll see 16,7 mm Xmax versus the manufacturer stated 16,75 mm. You can also enter 16,75 mm Xmax and Hg = 10 mm and they will autocalculate Hc to 43,5 mm.

Everything else is perfect.

You can see that if you use a box of the same size, that the rolloff on the lowQ is slower. The midQ rolloff is faster after ~40 Hz than the lowQ. Usually, a slower rolloff is better, but it depends on how you like your sound.

lowQ is also usually better if you want to build a ported box.

Depending of the size of the sealed box, the lowQ SPL is higher over 70 Hz and higher under a certain frequency. For a 1 cu.ft box, the lowQ have better deep bass under 25 Hz. For a 2 cu.ft box, it's under 17.5 Hz.

In a 2 cu.ft box, you will see that the lowQ can take more power before going in overexcursion. If you use the full 400W of power, under 25 Hz the lowQ will be in overexcursion, but in the midQ it will be under 33 Hz.

I hope I helped you a bit hehe! :)

wattz 27th April 2005 04:55 AM

Thanks for the tips Siimon5 :D I did the modifications to Xmax and it's right on the money! If anyone plans on using Infinity Kappa Perfect 12D VQ's. I'll keep these files online in case they want to use them.

I'm still indecisive about what configuration to use. Since I'm going to be listening to electronic music.. specifically house & techno music which uses a slightly tighter bass response than stuff like hip hop. It also has a faster beat, a lot of punch and deep deep basslines. In addition, this will also be used for my production studio which requires a more accurate and tighter frequency response. Hell, these are 400 W drivers x 2 and I don't need to sacrifice quality and gain more SPLs by putting ports in it or even making it bandpass. I been reading lots of reviews on these subs and a lot of ppl say they sound better in a sealed design.

So I might just make it sealed at 2-3 ft^3 each. But if a great vented design works better then I'm up for that too. Still haven't made my decision. I have been racking my brain trying to find the best possible design with the proper Q configuration:smash: Any more input would be appreciated.

simon5 27th April 2005 05:58 AM

Ported is good if you want your subwoofer to be flat in room down to about 20 Hz without EQ. You could do that with a 3.25 cu.ft internal box tuned to 18 Hz. It would need to be build with a very long dimension to accomodate a 29 inches long 4" diameter port. You could build a big 6.5 cu.ft box and put both speakers inside it. If you like the look of sonotubes, it would be a great idea. By tuning it under 20 Hz, you put the group delay out of the passband, so you won't have the usual ugly sound of a ported subwoofer and you will have all the precious output.

For sealed, I would go lowQ in a 3 cu.ft box. You would gain about 1 dB in the 30-40 Hz band using midQ, I think it's not worth it IMHO, especially if you plan to crossover your subwoofer higher than 50 Hz, because the lowQ take back the lead over that.

If you choose midQ, it will be good anyway, you may prefer the sound of it, I don't know. It's easily swapable anyway! Same thing if you go ported, not hard to block the port if the sound is not correct for you.

Good luck!

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