Infinite baffle vs Large sealed - AVS Forum
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post #1 of 11 Old 09-26-2012, 07:46 AM - Thread Starter
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Since my theater build is taking so long, I've had lots of time to look at sub options. Right now, the Fi IB318 seems to be the best displacement-per-dollar by FAR.

My question is this: Will there be any issue (sound-wise or mechanically on the driver) with using the IB318 in a sealed enclosure at about 2.5x vas versus a true 5-10x vas infinite baffle arrangement? Qtc for the large sealed comes out to about 0.66 (no leaks, well stuffed) for roughly 900 liter enclosure and with the performance of that driver, I'd really like to go that route, unless I change my mind yet again. rolleyes.gif I understand that it may not be as 'good' as a true IB. Has anyone used the IB318 in a large sealed? KryptoniteWhite used them in VERY large ported, I know.

TL:DR - Will a large sealed perform well versus true infinite baffle?

Thanks.

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post #2 of 11 Old 09-26-2012, 08:38 AM
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While the boys are formulating an answer, can i ask a few questions ? Whats the size of the room ? What amps and XO/EQ do to plan on using... You said theater, is this 100% theater use, not that it matters any, just curious....


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post #3 of 11 Old 09-26-2012, 10:42 AM - Thread Starter
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Most of that info is in my theater build thread in my sig, but to put it somewhere easy to find, the room is 13 ft wide x 20 ft deep. Not sure on amp, and we'll see if I need any eq after my receiver takes a crack at it (miniDSP if I need one). And it will be 100% movie/gaming.

I'm planning on doing two large sealed boxes 2 ft x 2 ft x 8 ft in the front with my mains all behind an acoustically transparent screen.

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post #4 of 11 Old 09-26-2012, 11:10 AM
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is your goal to go LOW more than it is loud? That big of a sub you can make some nice horns

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post #5 of 11 Old 09-26-2012, 12:53 PM - Thread Starter
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My goal is to go low. My room is small enough I don't need a whole lot to go loud. People hit very impressive levels with two of these in much larger rooms in an IB.

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post #6 of 11 Old 09-27-2012, 07:04 AM
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IB and sealed boxes are a continuum with output determined by cone displacement. With no EQ, the tendency will be for the lower Q IB to provide slightly more VLF output than a smaller box with higher Q. Download UniBox or one of the other box programs to run the numbers for your driver.

Paul W

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post #7 of 11 Old 09-27-2012, 07:09 AM - Thread Starter
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I guess I should have mentioned that I already ran winisd simulations. Response curves and group delay are very similar. Power handling needs a bit more juice for the sealed box vs IB, as expected. But I was hoping to get a bit of insight on the sound. I guess it's hard to describe how something sounds with words, but people talk about IB being 'no box, just bass'. So I guess I'm asking if having large sealed will help to remove the 'box' influence on the sound.

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post #8 of 11 Old 09-27-2012, 08:00 AM
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Quote:
Originally Posted by SilentJ20 View Post

I understand that it may not be as 'good' as a true IB.
Not necessarily. First off, sealed and IB is technically the same thing. Infinite Baffle defines an enclosure where the front and back waves do not meet. Originally that meant sealed. Fairly recently the IB name has been applied to in wall/in ceiling/in floor etc applications which are infinite baffle as well, though in truth they operate more as open baffle, with said baffles being very large.
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I guess I should have mentioned that I already ran winisd simulations. Response curves and group delay are very similar.
Then they'll sound similar. Ignore group delay, it can't be heard in subs. What can be heard is over-excursion, so the maximum SPL and excursion plots are pertinent, and may show that a sealed cab works better, especially as few IB 'rear chambers' are airtight.

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post #9 of 11 Old 09-27-2012, 08:43 AM
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Quote:
Originally Posted by SilentJ20 View Post

KryptoniteWhite used them in VERY large ported, I know.

Yes and he destroyed the drivers.

The motor structure of the IB3 isn't designed to be used in anything but an IB/OB.

If you want to use a sealed or ported box get the Fi .Q18's


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post #10 of 11 Old 09-27-2012, 11:01 AM
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Quote:
Originally Posted by pnw View Post

IB and sealed boxes are a continuum with output determined by cone displacement. With no EQ, the tendency will be for the lower Q IB to provide slightly more VLF output than a smaller box with higher Q. Download UniBox or one of the other box programs to run the numbers for your driver.

+1

Unless you already have the 900 liter enclosure, I'd suggest going with multiple smallish subs. The bottom line is that you need lots of displacement. Depending on how much enclosure size you shove that displacement into you will need either a large amount of power or a small amount.
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post #11 of 11 Old 09-27-2012, 11:30 AM - Thread Starter
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Quote:
Originally Posted by Thomas-W View Post

Yes and he destroyed the drivers.
The motor structure of the IB3 isn't designed to be used in anything but an IB/OB.
If you want to use a sealed or ported box get the Fi .Q18's

Thanks Thomas-W, I wasn't aware he destroyed them.

The Q18's do still provide very similar performance and price-wise, it's not too bad.

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