The manual of my devil Impaq 8000 receiver states that speaker cables with at least 1.5 mm2 should be used. However, cables with 1.0 mm2 are included in the scope of delivery*,

The cause is an error in the operating instructions.

You can use cables as small as 1.0 mm2 for this system to connect the Impaq receiver to speaker cabinets.

*Cables only included with certain offers.