Always happy to leave a like on your content. One of the most underrated RU-vid channels in the home audio world for interesting experiments and setup tweaks. Wishing you all the best on your future content.
That difference at 35Hz seems quite unusual to me. Copper cables like that should be fairly flat down to DC. I wonder whether the mechanical construction of the cable assembly of the DIY version is physically damping out the resonance better than the REL cable? Have you tried putting a heavy slab, maybe granite, on top of the sub woofers for stability?
