Cult of the Infinitely Baffled

IB- F.A.Q.
1)What's an IB?
For purposes of this forum, an Infinite Baffle is a alignment where the drivers are free-air mounted, in a space adjacent the listening room. They fire into the listening area through a common opening between the two areas. This can be the attic, basement, or any room with shares a common wall with the listening area.

2)Which space is best?
Any space that provides a mounting location for the baffle, offers adequate volume for the IB, and is close to the frontal boundary of the main speakers, is satisfactory.

3)How big should the space be?
The "rule of thumb" is that for each driver used, there should be a space no smaller 4 times larger than Vas of the individual driver. That is then multiplied times the number of drivers. 10 times Vas is considered optimal.

4) How many drivers should I use?
This is a difficult question to provide a general answer. In a small room 2-12"s should be adequate. For larger spaces or for high output, multiple 12"s or 15"s are desirable.

5)Won't the drivers be damaged without the benefit of being mounted in a box?
There is no more cone excursion in an IB than there is in any other "regular" alignment.

6)How do I choose a driver?
Chose a driver preferably with a 1/2 roll rubber or foam surround. Accordion surrounds are limited in their usefulness. Then look for a woofer with a Qts that is in keeping with the sonic characteristics you want.

7)Which Qts should I chose?
For an IB, the Qtc of the system is the Qts of the driver. If you like very tight bass, chose a lower Qts driver. If you like the "HT" sound, then chose a driver with a higher Qts. Dual voice coil woofers can be used with a variable resistor in series with the inputs of an unused VC. This allows the "Q" to be adjusted to the listener's wants/needs. One drawback of this is that the power handling is cut by 50%.

8)Will any driver work?
Most "normal" woofers satisfactory for sub use in sealed or ported designs will be satisfactory. Access the forum for guidance in choosing an appropriate driver.

9)Won't the heat of an attic harm the driver?
If a driver is suitable for use in a car environment, is usually acceptable for use in an attic.

10)If I need/want multiple drivers, must I cut a large hole to mount them?
There is a mounting system called a "manifold array" or "transition box". This allows multiple drivers to share a common opening. Access the forum for specifics regarding this topic.

11)Do I need a large power amp to drive an IB?
The IB will be as efficient as the woofer's rating, with expected increases if additional drivers are utilized. So chose you amp accordingly.

12)Will an IB vibrate the entire house?
Yes, especially if placed in an attic or basement.

References
- https://web.archive.org/web/20010420103214/klone-audio.virtualave.net/page101.html