Voigt’s design is a tapered tube, tuned to a quarter-wavelength of the lowest frequency to be reproduced. It is a simple, straight taper but has elements of horn-loading and is designed for corner-loading. The BIB maintains the corner position but goes a step further, tuning to a half-wavelength (twice as long) with the opening – or mouth – pointing upwards. The BIB still utilises corner-loading but the sound radiates unobstructed across the room by utilising the ceiling.
Builders in the DIY community have reported excellent results. The BIB calculator is available here and we have produced two enclosure designs for the Jordan Eikona 2 full-range drive unit.
The first Eikona BIB is designed for a single Jordan drive unit. Although the enclosure is over 2 metres tall, it is an elegant column (28cm deep by 18.25cm wide) which is easy to integrate in most modern living rooms.
A second design uses two Eikonas per enclosure for greater bass and power handling. The height is similar but with a slightly larger footprint (35cm deep by 24cm wide) – not substantially more than a stand-mounted bookshelf speaker but with considerably greater performance.
You will find both designs in a PDF here. The design lends itself to considerable fine-tuning depending on the amount and placement of the internal wadding. Much of this will be dictated by the finished loudspeaker’s performance in your own listening environment. It is also worth considering some form of grille over the mouth of the enclosure – you don’t want to lose the cat in there!*
As ever, if you decide to build one of our enclosure designs, we are happy to answer questions along the way and help where we can.
* A DIY horn loudspeaker design in Hi-Fi News magazine in the 1960s or 70s featured the feline damping technique. The author said his cat often slept in the mouth of the horn and claimed that the loudspeaker always sounded better when it did! He never found wadding to match the effect of a curled up cat snoring quietly in his loudspeaker.