At first sight, the construction of the VOX 251 HE-DIPOL looks complicated, which is why it is worth looking at each internal part individually first. Note that you must always differentiate between the left and the right speakers. The mid- to high-range unit which is positioned pointing at the main loudspeakers must always be connected in phase and the one facing the other way inverted. The tunnel is also on the side facing away. In the lower part of the cabinet, you can see the tunnel, made up of the base and an upper board, facing to the rear. In the middle, there are three cross-reinforcements. At the top of the cabinet, behind the cut-out in the baffle for the mid- to high-range unit, is the enclosure required for the mid-range cone, made up of two wooden boards. There are two mid-range chambers. Fitting the TIW 250 into the side is a special feature. The mounting board for the TIW 250 (346 x 297 with a 232 mm cut-out) itself is glued in place from inside behind the square cut-outs in the corresponding side panel. This means that the bass driver can be sunken by 19 mm (19 mm = thickness of the boards). For optical reasons, and to enable the cloth-covered frame to be fitted exactly in place, the side panel cut-out must be made extremely accurately. The frame can be made from a 16 mm board, in which a cut-out is made the same size as the outer diameter of the TIW 250 outer edge. The outer dimensions of the frame should be exactly 1 mm smaller than the opening in the side panel all round. In this way, the frame is jammed in place by the fabric used to cover it and alternative fixing methods (frame dowels) are not necessary. The crossover unit is mounted on the wall behind the bass port.

The damping uses one mat per medium range cabinet. The remainder is distributed evenly throughout the cabinet. Leave the space above the tunnel opening free as far as the lowest reinforcing piece. If, as a result of the acoustics in the room, the low-range bass is too powerful, dampingthis area up to the tunnel opening will have a corresponding effect on the overall bass output level.