Newby wants a book! (or something)

[wad4ever]

Hi, I'm building my basement next month, and I keep hearing that I should build an "Infinitely Baffled" subwoofer.

I looked at the photos here, and noodled around a bit, and I have learned a couple of things, I think.

Basically, IB just means that you use part of the house as a speaker box, right?

In my basement, there is an area under the stairs (at the back-left side of what will be the seating area) that when enclosed will be 3' x 3' x 6' in volume. The 3' x 3' area faces the projection screen, though it is on the left wall.

I'll draw a picture:

--------------
|   screen   |
|*    *     *|
|            |
|            |
|           R|
|*    P     *|
|            |
|            |
|   *    *   |
-------      |
|^^   |      |
|     |-------

This is a top view of the room. People sit in the middle, facing the top of your screen. The ^^ marks where the IB speakers would face. It's right on the floor. The * are speakers, the R is the receiver (on a high shelf), the P is the projector, and the screen is where it says "screen".

Anyway, this seems like it would be a good candidate.

I need a guide, a book, or something I can use to teach me how to build an IB, how to select an amp, how to select a speaker (or speakers?), and how to wire it.

The most urgent thing I need to know is what wiring to put in before I sheetrock. I want all the wiring to be accessed by wall plates on the wall next to the receiver, so I need to know what kind of cable to buy (it will need to be 32 feet long, minimum) and what kind of jack to buy to go on the wall plate. I do know that subwoofers take line-level signal, so I need good shielding on the cable that runs in the wall. I think it's just an RCA plug that connects the receiver to my wall jack, right?

Thanks!

\/\/ /-\ [)

[formica]

I think this is what you are looking for:

Main IB FAQ page
home.comcast.net/~infinitelybaffled/

Generic Design/Build/ Install FAQ Pages
home.comcast.net/~infinitelybaffled/page2IB-IBmanifold.html

It's much shorter than reading a book and most of your questions already made it to those two FAQ pages...

[lhreeves]

This site is pretty much the closest thing you are going to find to a how to book. Look in the Frequently Asked Questions section. Also read some of the other threads to see what problems others have had and what the solutions were. Typical configuration is LFE/Subwoofer out from the reciever to a parametric equalizer (usually a Behringer BFD 1100 or 1124). From there you go to an amplifier sized appropriately for the number of drivers you intend to use. Then you have your speaker leads that go out to the drivers from the amp. The volume of the area for the back wave of your drivers should be 10x the VAS of your drivers optimally but no less than 4x VAS. Amp and Cable sizes are matters for debate. Personally I am going to be using a BFD 1100, a Nady XA900 amp, 4 AE IB15 Drivers and 14 gauge wire runs.

[wad4ever]

Okay, it looks like the location I was considering will not be good. Right behind the screen will be a "window seat" under a window. I can take that box, and mount a bunch of speakers on the front of it.

My question: According to the link provided, "it can take 2 to 4 times more drivers in an IB, to equal the output of a box sub". So, why IB? Why not just a sub? Is it the expense, the sound quality, what is it about IB that is "better" than a boxed subwoofer?

Thanks!

[cjd]

IB for the sound quality and the bass extension.

IB's play with ease MUCH lower than most systems usually do, which takes displacement. ANY sub will require the same displacement to reach a given SPL at a given frequency.

Now, were you to port you may be able to get the bass extension on fewer drivers but you give up other things - among them you usually have a very large box in-room and the sound quality is not really there.

An IB is just kind-of effortless sound.

For reference, I built a sealed Tumult (Adire 15" with 34mm XMax IIRC) with the Adire ADA1200 amp for my dad. It goes low - it has the displacement. At the time, the driver was $500 and I got the amp on their early bird special - so $1000 into the project (plus box).

It did not manage the sound quality of my dual Dayton 15" IB sub with 240W plate amp. It was very VERY good, but still just not there.

That's the other thing about an IB. You don't need a lot of power relatively speaking.

C

[ThomasW]

In a standard 'sub' the output of the driver/drivers is colored by the interactions with the smallish box. Since an IB basically has no 'box' there are no box induced colorations.

There's more to it than this, but that's one basic reason why IB's sound so much different and better than a standard box sub.