Sealed 18" DIY Sub - how much can Dirac boost? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 7 Old 07-17-2019, 01:18 AM - Thread Starter
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Sealed 18" DIY Sub - how much can Dirac boost?

Hi guys,



Don't really know if I should post this in a Dirac specific section or the DIY speaker section, so here goes nothing...


I'm in Australia so not so attractive price-wise for me to get some of the Seaton F18's but was thinking about replicating Mark's concept: high-powered, sealed and with (at least I believe that's the case) heavy EQ at the bottom end to counteract the sealed slope.

I've outsourced the cabinet making and want to have a sealed box built that's slighlty larger than the F18 and is passive so should give me a littble bit of extra internal volume.


If I fit in the Dayton UM18 and provide it with copious amounts of power along the lines of what Mark provides in his, how much would I need to EQ this sub to make it go a low as possible?

And more importantly: would this fall within the possibilities of Dirac or would this need to get done by a separate, manual EQ?



I suspect that, given that Dirac will measure the sub first and that there are inherent limitations to the sealed design, I may not be able to boost the low-end sufficiently with Dirac alone as Dirac is limited in the amount it can boost.

Am I correct in that assumption?


If so, then I will have to revisit my choice in amp to drive this sub.


Thx in advance for your insights!
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post #2 of 7 Old 07-17-2019, 05:03 AM
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what subwoofer amp and receiver/processor are you using?

- 6 BA CR6 array center channel, QSC AD-S82 L/R, 4 jbl 8330a surr , 8 jbl 12" subs w/Inuke 6000. JVC rs420, Denon x4000, Sony x800 -
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post #3 of 7 Old 07-17-2019, 08:13 PM - Thread Starter
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Quote:
Originally Posted by trilkb View Post
what subwoofer amp and receiver/processor are you using?

I'm using a NAD 758v3 as a receiver with Dirac Full.


Amp-wise currently using a Behringer EP2500 mono bridged for a DIY 18" Sonotube with a Mach5Audio IXL18 driver.
Would be great if I could reuse the amp which is why I'm wondering if Dirac would be enough to boost sufficiently to and below 20Hz in a sealed system with UM18. But am open to other options in case I would require more power...
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post #4 of 7 Old 07-17-2019, 10:23 PM
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DIRAC itself won't boost that much, but it really depends on your gains. You can perform some trickery though, both with gains and Dirac targets. Worst case scenario you can put a minidsp 2x4HD in line, use it as a parametric EQ, and let DIRAC think that's the native response. You can also reduce the main target by 5dB or so for a little extra headroom. You have lots of options.

I use a minidsp to reduce the higher subwoofer freq peaks, add some boost down low, then let DIRAC take over -i.e. get 'er close. As such I'm running a target curve that's about 15dB hot at 16hz vs. 20khz.


As far as what the ultimax will take, it's a great driver but still a sealed 18, so don't get too crazy or you'll run out of excursion in a hurry. Depending on how loud you listen, 20hz is no problem and possibly quite a bit lower.

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post #5 of 7 Old 07-18-2019, 04:44 AM
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Thats basically what I was getting at. Youd run any EQ you can before letting your receiver take over. A minidsp 2x4 HD would help a lot if the sub amps have no EQ.

- 6 BA CR6 array center channel, QSC AD-S82 L/R, 4 jbl 8330a surr , 8 jbl 12" subs w/Inuke 6000. JVC rs420, Denon x4000, Sony x800 -
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post #6 of 7 Old 07-18-2019, 01:20 PM
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Cut dont boost. A low end shelf can be used however the total level needs to be reduced by the total gain produced by your shelf or peq filters for a net gain of zero.


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post #7 of 7 Old 07-20-2019, 03:21 AM
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I have six sealed 12" subs powered by an EP4000 and I only use Dirac for the boosting. It can boost up to 10dB so as long as you place your subs wisely there is no issue at all to only use the boost provided by Dirac. I run three of my subs nearfield and three in the front and I can play to 7Hz so that the couch shakes like crazy. So I'd say it can boost enough no issues.

I see a lot of people building very small sealed cabinets and what happens there is that you get a much sharper roll off with peaky mid bass. For an 18" driver I'd not build a box smaller than 200 liters. With the correct box you don't need to boost that much and it has a lot of other benefits as well like overall sound quality, less compression and heat etc.

Room| Treated | Sound| Front: Ino Audio i32s, Center: Ino Audio i16s, Surrounds: 6 x Ino a2, 6 x Ino a1, Subs: 6 x Ino Infra-Y|
Picture | Epson TW9300, Seymour Center Stage UF 130.4" retractable 2.35:1 |
Electronics | Arcam AVR390(Dirac Live), 3x Ncore nc400 monoblocks, Emotiva XPA-2 Gen2, EP4000, Panasonic UB700, Allo Katana + Isolator 1.2(Roon bridge/DAC), ATV 4K |
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