Why infinite baffle? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 12 Old 12-12-2019, 10:13 PM - Thread Starter
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Why infinite baffle?

Can someone explain in very basic words what is Infinite Baffles any why it is popular? Pros & cons. Where does it shine and are their draw backs? I’ve had a few people recommend IB subs. However all the discussions are always way more advanced and I grasp some of it but I feel I’ve missed some of the basics.

I have some further questions but I’d like to have a thread that starts at with the simplest concepts then can gradually get deeper into the topic.
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post #2 of 12 Old 12-12-2019, 11:01 PM
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Hoffman's iron law states, pick any two of the three categories at the expense of the third; size, freq response, efficiency.

So if you want a box that's efficient and small, it won't go deep.

If you want a box that goes deep and is small, it won't be efficient.

If you want something that goes deep and is efficient, it'll be very large.

Infinite Baffle falls into this category; essentially a huge sealed box, you just don't have the issues reproducing low frequencies that you do when put in a small box (not much/no air spring to contend with).

If you have the option to do so, it's awesome and worth a shot.
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post #3 of 12 Old 12-13-2019, 01:33 AM
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building on what chris said, the point of a sealed box is to block the front wave of the bass from the driver from contacting with the wave from the rear of the driver.

a sealed box however has air that the cone has to move against--pushing the cone inward raises pressure in the box and requires more amp power the smaller the enclosure.

with a large sealed box that air pressure is reduced, so less amp power is require to move the cone to its full excursion.

an "infinite baffle" concept is just turning the room into one giant speaker box.

as a result very little amp power is required to move the cone.

without all that air pressure fighting against the cone motion, some folks report a cleaner sound too.

the biggest practical advantage of infinite baffle is that it doesn't require putting big boxes in the room.

big boxes can have their advantages though too. ;-)
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post #4 of 12 Old 12-13-2019, 02:05 AM
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Quote:
Originally Posted by Mharper3 View Post
Can someone explain in very basic words what is Infinite Baffles any why it is popular? Pros & cons. Where does it shine and are their draw backs? I’ve had a few people recommend IB subs. However all the discussions are always way more advanced and I grasp some of it but I feel I’ve missed some of the basics.

I have some further questions but I’d like to have a thread that starts at with the simplest concepts then can gradually get deeper into the topic.
Pros:
- Deepest bass possible
- Cleanest bass possible
- Natural sound of drivers no colorization by box
- Actually pretty inexpensive compared to many other alternatives. My 4 Fi drivers + amp was about $1300 total.
- A pretty easy DIY option much simpler than building a box.
- Great for movies and music.

Cons:
- Lots of space required for baffle
- A DIY option, you must build the baffle, secure the drivers etc.
- Ruins the enjoyment of all other subs. You will hate the subwoofer in your car or office after hearing an IB setup.

I have built 4 infinite baffles arrays and they all sounded awesome.

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Video: JVC RS4500 135" screen in pure black room no light, htpc nvidia 1080ti.
Audio: Anthem mrx720 running 7.1.4, McIntosh MC-303, MC-152, B&W 802d3 LR, B&W HTM1D3 center, B&W 805d3 surround, B&W 702S2 rear, B&W 706s2 x 4 shelf mounted for atmos, 2 sub arrays both infinite baffle: 4x15 fi audio running on behringer ep4000 + 4x12 fi audio running on 2nd ep4000.
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post #5 of 12 Old 12-13-2019, 08:06 AM
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One of the biggest cons is that your house will get the back wave of bass or the same bass your room is getting with the driver. To combat this I built a giant wall inside my room. Another con is placement is crucial, make sure you know the spot the drivers are going in have a good response!
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Building the room, speakers, and subs.
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post #6 of 12 Old 12-13-2019, 08:35 AM - Thread Starter
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Placement just feels like a shot in the dark. I know a lot of people will do the crawl test with subs but when you are planning on having your subs in the ceiling it’s not like you can just move them if you don’t like where they are going to go.

Any suggestions on how to figure out placement in this application?
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post #7 of 12 Old 12-13-2019, 09:05 AM
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I agree with the above, especially that all other bass doesn't sound as good. I have had multiple sealed and ported set ups but the best sounding bass in my opinion is my IB set up. For location, I placed a capable sub at my MLP and measured around the room with REW to find the spots. My results weren't perfect but much better than guessing. In addition, I was able to run 12, 12" drivers off an inuke1000DSP with ample head room.
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post #8 of 12 Old 12-13-2019, 09:32 AM
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Comparing sound all depends on the quality of the build. We build something and it sounds poorly, is it the driver, cabinet, design, a combination? Do we have a leak, wired correctly, etc.. I would not say my IB was my best sounding sub as once everything was done correctly they all sound pretty much the same, especially using the same drivers. Right now I am using two RE XXX 18s, I had them in my wall which was 250 cubes, sealed and ported to 10hz. I had a flood and ripped my theater apart so now I built two 17 cubic foot sealed boxes. They sound better now, is it the box, the alignment, the quality of the build, who knows, they all sound great, this one is much smaller but still big enough to use the power necessary to get close to x-max at 10hz, it worked out great. They all rattled my upstairs equally bad. The nice part is I can run my two subs taking up 34 cubes just as loud(12 dB over reference) as my 8 18s taking up 250 cubes.

Building the room, speakers, and subs.
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post #9 of 12 Old 12-15-2019, 03:41 PM - Thread Starter
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Would it be better to have (4) 18s in 4 separate boxes or 2 boxes with (2) 18s in each box?.
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post #10 of 12 Old 12-15-2019, 04:31 PM
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If you do two boxes of two with opposed drivers, you can have significantly less mechanical vibration.
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post #11 of 12 Old 12-15-2019, 06:55 PM - Thread Starter
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Quote:
Originally Posted by markmon1 View Post
Pros:
- Deepest bass possible
- Cleanest bass possible
- Natural sound of drivers no colorization by box
- Actually pretty inexpensive compared to many other alternatives. My 4 Fi drivers + amp was about $1300 total.
- A pretty easy DIY option much simpler than building a box.
- Great for movies and music.

Cons:
- Lots of space required for baffle
- A DIY option, you must build the baffle, secure the drivers etc.
- Ruins the enjoyment of all other subs. You will hate the subwoofer in your car or office after hearing an IB setup.

I have built 4 infinite baffles arrays and they all sounded awesome.

Is there a reason you went with 15s instead of 18s?
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post #12 of 12 Old 12-15-2019, 07:11 PM
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Quote:
Originally Posted by Mharper3 View Post
Is there a reason you went with 15s instead of 18s?
Yea, my physical space was an issue. I didn't have the extra foot in width required and still fit my equipment rack in next to it. The Fi 15's and Fi 18's have the same sensitivity at 1 watt 1 meter away and most the time even when cranking these, the drivers are hardly moving anyway so there's tons of headroom. I could have tried to build more of a manifold but then they'd stick out more and my closet is only 3 feet wide so I wanted room to walk by and carry in things like that Mc303 which was ridiculously large and heavy. So really it was all just for physically fitting them in the space I had.
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Video: JVC RS4500 135" screen in pure black room no light, htpc nvidia 1080ti.
Audio: Anthem mrx720 running 7.1.4, McIntosh MC-303, MC-152, B&W 802d3 LR, B&W HTM1D3 center, B&W 805d3 surround, B&W 702S2 rear, B&W 706s2 x 4 shelf mounted for atmos, 2 sub arrays both infinite baffle: 4x15 fi audio running on behringer ep4000 + 4x12 fi audio running on 2nd ep4000.
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