No deterioration in sound quality
I did not buy these reducers for my Electrocompaniet ECI-5, but I tried them with this integrated amp first. I did not perceive any deterioration in sound quality compared to a connection with the bare speaker cable (Supra Cables Classic 4.0).
There is only one drawback: when using a cable with a large cross-section (in my case, 4 square millimetres), the screw used to secure the end of the cable cannot be screwed completely into the plug. This renders the sleeves (which are only slightly elastic) unusable. Instead, I simply used gaffer tape in two different colours.