My brother-in-law has finished his subwoofer system using a slightly different than normal setup. The system is called "Infinite Baffle Subwoofer"

What is different with this system is not using a standard ported or sealed box but using a room wall to stop the back wave from the driver from canceling the front wave.

Most sub system try to make some use of the back wave from the woofer, either for extra sound output ( bass port and 4 order systems) or to control the resonance frequency of the speaker. (Called FS)

The Infinite Baffle Subwoofer system is super simple, just cut some holes in your room walls and mount the drivers between the room walls, or use a box to load (combined) the drivers output and use a port or duct to direct the sound in to the room.
There is, of course, a website for anyone who likes the idea.

http://ibsubwoofers.proboards51.com/index.cgi

I can't make this type of system for my house because of my brick walls with no room on the other side, and a "special" hand patterned ceiling that my wife wont let me cut up. There is one wall that might work but I have to replace my A/C first.

This is a look at the two subwoofer boxes.

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The boxes do not act a a speaker box but just let the two driver couple the output of the drivers, this allows you to use almost any number of drivers you wish. This is good because the system is the least efficient of all the subwoofer systems. It can be modeled with software like boxresponse by selecting sealed box and make the box 20 times larger than recommended for the driver.

They call the speaker boxes a manifold and the manifold can be almost any size and hold many speakers, its job is to port the pressure wave into the room and hold the speakers. It this setup the other room is the garage. This means lots of sound will go out side for everyone to hear.

The drivers he selected are by Fi-Car. link

https://ssl.perfora.net/www.ficaraudio.com/

The model of the drivers is the SSD18, that list for $239 each they will cut you a deal if you buy 4

This is the look from inside the theater room looking into the speaker box.

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and another look.

The theater room is a little small but nicely done. Here is a longer shot.


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The 108" 2.8 gain screen is really bright in the middle seats.

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The PJ is a BenQ

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The sub amp is a Europower EP2500 that is rated at 300 watts RMS at 8 ohms. 2500 watts peak. This is a copy cat amp made in chine and it looks to really put out the rated power.

My little guy showing how big a 18" really is.

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I have been making speakers for many years and have heard lot's of expensive systems like this one.

http://www.legacy-audio.com/whisperspecs.html

The room I heard the legacy's in was a lot larger but the bass from the IB 4x18" system was much better!

The main thing is the bass extension. Normally the speaker box will raise the Fs of the speaker. (the resent frequency) The Fi-Car has a Fs of 24Hz and when mounted in a bass port box it will tune to 33Hz or so and the sound pressure will drop off at 24db per octave as you get lower than 33Hz. ( thus at 16Hz the response will be 24db lower, or almost nothing).

A sealed box has a much better roll off at 12db per octave but a sealed box will push the Fs up a little higher to start with so perhaps 36Hz or so, but will make better bass at 25Hz, over a bass port system. But a sealed box is only half as loud and the woofer has twice the exertion of a bass port box, The sealed box does have better support at the lower frequencies which helps to keep the voice coil in the gap.

A Infinite Baffle woofer system will have about the same rolloff as a woofer response curve or about 12 to 6db per octave. The main thing here is the starting point of the rollloff is at about 24Hz! So at 20Hz it is not really down in response at all!

They say the response is not flat and I believe them, but the sound has a non boxy, non resonate, DEEEEEP punch that I have never heard anywhere with any system ever! It will shake all the walls and the sofa and still not seem too loud.

I do think that 2 woofers would have done fine for this sized (12x20) room. He had the power set to less than half and the subs were barely moving. He also has the speakers wired to 8 ohms so he could wire to 2 ohms and get more power but if you would have to be more than a little crazy to to that, or get a second amp for a 5000 watt system!

If anyone would like more info just join the Infinite Baffle forms and learn about the other system people have built. You will love the sound.

The OB (Open Baffle) speakers I use have the box-less sound but don’t need the extra room. The disadvantage is they are even less efficient than the IBs. To get around it you choose drivers with large xmax and a qts of about 0.6 and use brute force to power them. Might be an option for you.

DJ

I still may be able to do an IB inside if I use the closet in the back of the room. I still have yet to start the RPTV but I may just go with a single 15" in a transmission line about 6'x20"x17" standing behind the RPTV.

But first will be a 15" for the backyard theater. I am going to try a 8' long folded transmission line tuned to 21Hz or so. I will do a small plog on it too.

with the IB its alot less 'punch' am I correct? i have near heard any only read about them.

If you mean unexaggerated 50 Hz, then yes they are very smooth.