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Need help : sealed infinity kappa perfect 12.1
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Old 9th July 2018, 11:53 AM   #1
gadut is offline gadut  Indonesia
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Default Need help : sealed infinity kappa perfect 12.1

this is my first subwoofer build, hence I'm still guessing and relying on modeling software. Previously i read on my friend's built which used DVC of this subwoofer, when looking at good price of this item without breaking my wallet and good result on simulation, i think my friend had a good choice on drivers.

However they are discontinued, but I'm lucky to get second hand item - 3pcs already, looking for 1 more - but they are single voice coil version. When I put into online simulation, it seems SVC has lower Fb than DVC but double in box volume which is not an issue since this is for home subwoofer.

When i google on recomended box, most of the thread lead me to car subwoofer which ended between 1-1.25 cu.ft volume but simulation give me 2.2 cu.ft. I have no issue up to 3 cu.ft box volume.

Can i rely on software simulation for box volume? which volume should i build? i will use 2x18mm plywood with internal bracing and powered by nu3000dsp.

It will be very helpful if anyone can share any experience on using SVC of this item for home sealed subwoofer.

btw this is just for stereo music, no plan to make any home theater
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File Type: jpg IMG_20180703_084546.jpg (54.0 KB, 73 views)
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Last edited by gadut; 9th July 2018 at 12:11 PM.
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Old 9th July 2018, 01:26 PM   #2
snappyturtle is offline snappyturtle  United States
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go with 2 cubic feet and let it rip. the rec'd box volumes on the spec sheet are for car audio purposes. they rely on cabin gain to boost the low end, and use smaller than normal box sizes for sustained abuse.
so unless your listening room is about the size of a normal sedan, better off with the larger volume.
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Old 9th July 2018, 02:26 PM   #3
gadut is offline gadut  Indonesia
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thanks for the advice, i just remember about target Qtc of sealed which is usually targeted as 0.7 which seems i might use 2.2cu
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Old 12th July 2018, 06:36 AM   #4
gadut is offline gadut  Indonesia
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Default series push push

my original plan was to build 1 driver on each box, but i think why not build push push directly. but the problem is that with 4ohm driver and nu3000dsp, i have no choice to put them in paralel and I rarely or maybe never read anyone post on their build by series connection.

I read that it might cause driver imbalance because voice coil act as voltage divider, but how significant is it for below 80Hz duty?
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Old 12th July 2018, 05:05 PM   #5
GM is offline GM  United States
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Nothing wrong with series other than inductance increases, which with SS and a low XO point is not an issue. For individual driver protection though, I would wire them in 4 ohm stereo.

As for a target [damped] Qtc, if these will be driven hard enough to get/stay heated up, then system Qtc [sysQ] will rise, so the cab can further protect the driver at a loss in sound quality, which may not be noticed down this low; or for HIFI/HT, start with a larger cab/lower sysQ.

GM
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Old 13th July 2018, 01:31 AM   #6
gadut is offline gadut  Indonesia
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Thanks GM

I have attached WinISD simulation for this dual series arrangement. however WinISD only give parallel option, it can't be changed. with Q 0.707 the volume will be 112ltr, do you have any target Q estimation for that compensation? increasing the volume into 140Ltr resulting Q into 0.664.

btw, I find that T/S parameter for Vas provided by WinISD (83Ltr) vs is different with downloaded PDF (100Ltr). which one is usually correct?
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File Type: jpg IMG_20180712_205125.jpg (611.8 KB, 34 views)
File Type: png kappa.png (66.6 KB, 33 views)
File Type: jpg Capture.JPG (102.2 KB, 31 views)
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File Type: zip Infinity Kappa Perfect 12.1 - Dual.zip (1.0 KB, 1 views)
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Last edited by gadut; 13th July 2018 at 01:39 AM.
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Old 13th July 2018, 08:49 PM   #7
GM is offline GM  United States
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You're welcome!

Not really beyond make it as large as you can tolerate since in some HIFI/HT apps the driver's Qts can double in [sub]bass heavy soundtracks, requiring this driver to be tuned to the transient perfect 0.5 Qtc and maybe still technically too small, so some form of hi-pass EQ is normally used.

Probably neither since apparently WinISD calculated Vas Vs the pub's measured spec; IOW they should have matched and a good way to check accuracy if enough specs are provided; so again, when in doubt go with whichever calculates the largest cab for any baseline cab alignment to start with if for no other reason than it's a lot easier to 'shrink' it than enlarge it, though sealed is much more tolerant of cab net Vb tolerances than vented alignments.

GM
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Last edited by GM; 13th July 2018 at 08:54 PM.
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