Quad 18 in-floor Infinite Baffle Subwoofer

Just finished building this project and tested it out full-bore today.

Listening Impressions:
-There is no need for tactile tranducers with this setup. The floor literally ripples, bouncing the couch upon it like a small toy.

-It sounds nothing like any other subwoofer I've ever heard. The sound is so clean and uncolored that it is... transparent. To be honest, I thought something was missing at first. It turns out, something is missing... all the extra distortion every other sub I've ever heard made. Now I can hear every part of a sweet bass line. The veil has been lifted.

Parts:
-4 Ficar IB3 18" drivers
-2 manifolds (2 drivers each) placed for smoothest in-room response
-1 Crown XLS5000 amp sending about 1000 watts @ 8ohms to each manifold.
-EQ'ed with Audyssey XT32 dual sub equalization (Denon 4311ci)
-Room is 1600cf, sealed. (13'x15'x8')

In-room appearance:

Basement view:


One thing I personally like about this type of subwoofer install, is that it doesn't require much finish work or getting the box/port size right.. because none of that matters much.
The fact there are no more giant boxes and wires in the room is nice also. Especially from a pet and child-proofing point of view.

I'm sure I'll get out REW again and eventually post the typical cool plots of flat response below 10hz.
Right now, though, I'm too busy listening.

Couldn't have made this without all the great ideas I got from all the smart people here over the years.

I used 14"x20" grates. They fit between the floor joists. You can find any size grate you want online. Generic ones like I have cost about $30 each.

I wasn't planning on posting a lot more build details on this thread, but I guess I'll throw up a few things. Maybe someone will see this and say "what the heck is an infinite baffle subwoofer??!!?" and start doing some research, as I did years ago.
Lookup "The Cult of the Infinitely Baffled" for more information.

I think its a great option for those who have the space for it. Arguably the ultimate subwoofer type.

I don't know, I just followed what others have done. They have been building subwoofers this way for over 15 years with no issues. I'm told these act like a giant compression driver, not a transmission line, whatever that means.

One of the big reasons I built this type of subwoofer is that you don't need to worry about things like port tuning. Just make a box big enough to fit the drivers, clamp it to the floor joists, and go. It's really that simple.

Some people have made these with *tiny* manifold openings (like a 4"x10" slot) and had a small reduction in response over 70hz, but that's an extreme situation.

I can't wait to demo an intense LFE scene with someone who doesn't know about these and thinks they are just air vents. Should be... funny.

As a childish experiment, I put a piece of paper over one of the grills and then played the Cloverfield scene. Pretty funny watching it levitate and ripple.

Thanks for the input, alway enjoy seeing various DIY projects.

Ok, after "breaking" these in for a few weeks, I decided to see how far I could push them.

I broke out all the "Sub-Killer" content I know about:

War of the Worlds
Bass I love u
Cloverfield
THX Amazing Life
...and a bunch more.

I played all of these at reference and sometimes a little above. This is probably at least 5 to 15 decibels higher than I would ever listen to anything in "real life". I'm hoping that with some more room treatments, this will be improved, as I really enjoyed the LFE effects at these high levels. (Turning the subwoofer channels up alone unbalances things, so I'm going to work on taming the highs)

Results: These subwoofers just laugh at any attempt to bottom them out. During War of the Worlds and Cloverfield, giant monsters are not only on the screen, they are under my home theater, punching the floor. The couch Is literally jumping up and down with the floor flexing. The "bass mushrooms" from the THX demo do their best to blow the windows out of the walls! But if you go down into the basement where the backwave is, there is really no drama except for a couple of loose paint cans rattling. The manifolds with their opposed drivers are vibration-free. The driver cones are using quite a bit of excursion, but making no noise, clicks or clacks. The clip lights on the amp are not even flickering.

I can only assume the room gain in this 1600cu.ft sealed room is quite large, and as a result, these things have plenty of overhead.

Yes, it's true, you can't really HEAR content below 20hz.... but anyone who says it is worthless has never felt the gut-wrenching physical POWER and MOVEMENT this content provides. Bass shakers and Buttkickers would be absolutely redundant in my system.

I have reached bass nirvana. Aside from adding a rotary subwoofer, it would be impossible for me to get better subwoofer in this room. Fin. Done. Perfection accomplished. Subwoofer upgraditis is no more.

First, I very much doubt you or the house would survive notnyt's at full volume. d

Both systems would have plenty of overhead, so the differences would be in the room response, EQ and any inherent differences between IB and what notnyt is using. There are two schools of thought... one says IB's sound so clean because of their design, and another says they sound so clean because of the amount of drivers they use, and the resultant low distortion. After using one, I'm SOLIDLY in the first camp. I predict you would hear a huge difference in sound because of the sealed vs. IB designs.
As to which one you would like, who knows? There are people who dislike the IB sound.
I also think one large positive of having a IB in the floor as I do is that the rear wave and front wave combine to flex the floor like a giant diaphram, which is a great effect worth pursuing, IMHO.


Looks just like my setup. I'm also using no highpass, and feeding these drivers with about 2X the safe power they can handle, but as I've said before, I've found no content with threatens them.
I'm not using any EQ except for XT32.


Hope you find a good place to install those BEASTS. Probably the most impressive drivers I've ever seen, and that includes the LMS Ultra.

There is a procedure for this? What does it measure? I've seen a few videos of it being done, but I must have missed the reasoning. Most of the videos are just kids doing it with car subs because it looks "cool". I don't think that's what you're talking about.

Someone on here said it would be a good test for IB subwoofers, but I never found out how to do this test.

Atlanta Supply Company

The 1530B model is the one I got. It's just a simple grate with no dampers. It is available in almost any size and is cheap. It's also meant to be walked on, so it's very strong. It's design means almost no air resistance. I countersunk it into the carpet by removing the carpet padding around the edges of the hole I cut in the floor. Vacuum cleaners and children run right over them with no worries or damage.

BTW, did you ever calculate the displacement of those drivers you are using? They may be an option for those who need 8 FiCar IB3's worth of displacement, but only have room for 4 18" drivers.... if they move a lot more air. (FiCar IB3 18's move around 7 liters each)