Dual 15" Sub

This is the only one of my early designs to be still current - must have guessed it right! Around the early Eighties, most PA systems were large separate box 3-way monsters crossed over typically at 250Hz and 1.6kHz.  Whilst these frequencies made sense for octave spread between bands, the commonly used W-bin subs just weren't capable of handling the job.  Their tight folds made the lower mids sound muddy and indistinct, and the compact designs had trouble getting below 80Hz. I figured a design with fewer and gentler folds would give better top end performance, even if it meant sacrificing horn path length.  I also reasoned that lack of ubrupt steps in the horn profile would also be of benefit.  Utilising all the generic horn calculations I could find at the time, and lots of paper, I came up with a design that used 2 15" speakers side-by-side firing into a gentle "C" shaped flare (hence these boxes became nicknamed "C-bins").  It used throats of 600cm^2, mouth of 4750cm^2 and path length of 100cm (1m), giving a flare rate of around 37Hz.  Design was centred around commonly available Australian Etone 805 speakers, rated at 250W RMS and capable of handling plenty of abuse. Although the overall efficiency did not quite match many W-bins (short path and all), the design goal of bandwidth was met quite well.  The box would happily go higher than 500Hz if needed ("hey, what did you do? - I can hear the bass guitar..."), and had kick down to 50Hz in direct radiator mode.

Box completed and ready for paint.  Note the cross bracing in mouth area to prevent excessive vibration of larger panel areas.

Two views of the throat assembly during construction.  The attention paid to mating the individual throats to the horn can be seen here, and I feel is one of the reasons this box sounds as good as it does.

Side panel left to install here.  This shows the gentle curve of the horn path.  Note that although path from throats narrows in vertical direction, it widens considerably to outer cabinet walls, giving the correct expansion.  Height of the cabinet is 1m, width 88cm and depth 67cm.

The boxes in 1990 (left) and 2002 (right) Since originally fitting these boxes with Etone 805 speakers, Etones went up markedly in price, while Eminence got more powerful.  Therefore current boxes use Eminence Omega Pro 15 drivers.  Four of these stacked as at left with 1200W pumping into each box certainly has some punch.

Construction plans for this box now available free !  email me to request them.

Here is the response using the Omega Pro 15 with 1W input power.