To this end, Vox adapted the standard AC-30 speaker enclosure for use with the AC-50 head. A horn would be added to the enclosure to boost the treble response. After listening tests were completed, the Goodmans Midax horn
was selected. It is important to note the Midax is a mid frequency, not a high frequency horn.
A 2 uf oil filled capacitor was wired in series with the horn as a mid/high pass crossover.
The location of the horn near the top of the speaker board required that Vox cover the entire front panel with grill cloth, a departure from the traditional AC-30 vinyl and grill cloth "split-front" cosmetic treatment.
When it was discovered that the Midax horn was too deep for the slender AC-30 cabinet, a hole was cut into the rear panel, allowing the horn to protrude about 1/2" outside the rear of the enclosure (see picture below). Vox considered this modified AC-30 enclosure to be a short term fix to address the immediate needs of the Beatles. Vox planned to design a larger AC-50 Mk II enclosure sometime in the future that would fully enclose the horn.