[VienH]

im not sure if i want to put my speakers in my ceiling and the attic would act as an IB. i heard the biggest benefit for OB is lack of box coloration. i would believe IB would have the same benefit + no baffle diffraction.

any input would greatly appreciated.

[mcgsxr]

IB is usually used for bass.  It allows for the air space "behind" the woofer to act as the enclosure.  The rule of thumb for the amount of space is 10X VAS of the woofer.

OB are often/usually run full range, and therefor the rear wave off the driver is used, after it reflects off the room and furnishings etc.

[JohnR]

It's a good question, and at one level there are similarities, but really they are completely different fish kettles. IB is essentially a very large box, so there is no interaction between the front and rear waves, and thus no cancellation at low frequencies, but also no side nulls which can (can, not necessarily, IMO/E) help reduce room interaction. As Mark says, IB is limited in frequency due to the structure.

I think there are probably two common elements, one being (perhaps) lack of "box coloration" as mentioned by the OP. although I could see some care would be needed to avoid issues related to vibration/pressurization with an IB, and the minimal air loading of the driver resulting in a "desirable" Qts of around 0.7 (or higher or lower depending on who you ask).

That's my 2c on an interesting question

[JLM]

Sound staging is affected which is why it's typically used only for lower bass (subwoofer) frequencies.  In open baffle (dipole) designs at those frequencies front and rear sound waves (versus directly sound rays, search Audio Circle for "constant directivity" and "Swarm") are large enough to cancel each other out along the plane of the baffle.  Mark is right about the 10 times Vas rule of thumb, but the space behind at that arbitrary point is large enough to not act as any kind of enclosure.  Some use attics or even exterior walls (preferable in temperate climates due to thermal transfer) as outdoors the bass energy quickly dissipates.  If using an interior back space care must be taken not to use rooms with hinged doors (swinging of large surfaces could pressurize against the driver and blow it out) or loose contents (sympathetic vibrations), so attached garages can be a viable option.