Probably the worst bit of "soldering" i've ever seen.
An intermittant fault with one channel speaker lines 2.7mm diameter over the
insulation, 1.5mm or so core, the 4 wires go to a rear board for speakons
and 1/4 inch outlets. Each wire is stripped neatly , leaving some whitish
thin coating over the copper core wires that probably holds the filaments
together until solder temperature melts it . Pushed through the large holes
in the solder pads and "soldered" on the blank side of the board with little
blobs of solder relying on melting of the board composite to hold in place,
and unmelted coating plainly visible on the other side. I assume the holes
are plated through or there would be no electrical connection possible. The
assembler must have soldered the wrong side.