Impedance measurement box
I used 100W power resistors, gave it 4 channels, 2 XLR and 2 RCA. I used symmetrical power resistors on the XLR to give it extra power handling capabilities. 10 Ohm as a reference for both. And then I put it all in the smallest box I could find to house it all.
Now I'm under no illusion that I can pump 600W into this tiny thing for more than probably a couple seconds tops, but I just tried it at 2x40W and it took maybe 15 minutes to reach 70°C on the outside, which is when I stopped. The thermal adhesive seems to be doing a fine job.
I wanted to be able to test drivers at higher voltages to check how the impedance would change. And simply have a nice box for impedance measurements.
Why? Because earlier all I had was just a 1/4 W resistor that I soldered between two RCA cables with another RCA as a source input. Thin wires as leadouts. All of the cables very short. It was terrible and I'm glad I no longer have to deal with that.