strange rel subwoofer cable phenomenon

I have found that interconnects usually make most difference at higher frequencies, as one would expect since it is the capacitance that is the key design parameter for interconnects, and the effects of capacitance are proportional to the frequency. Since the sub isn't carrying high frequency information you won't hear the difference.

The neutrik connection to the subwoofer is electrically quite different from the RCA connection so I'm not sure that you can infer from one to the other. However the neutrik connection is also from a very low source impedance (speaker terminals at the amp) to a very high input impedance (the REL input is really a voltage sensor). For this reason I would not expect a marked improvement from using expensive speaker wire, and I would even go as far as to say that speaker wire is the wrong wire to be using for the neutrik connection, since the connection to the REL is carrying virtually no current. It is probably better to use a low guage (say 24) PTFE insulated wire, not braided, to minimize the capacitive load on the amplifier.

Having said all of that the proof is in the listening, so if you have can demo the cables then give it a try and let us know what you find.

Not to worry. In objective tests most people cannot tell the difference. You're being objective, you're listening. So much (incorrect) hype and BS about wire. Save your money and enjoy.
Curt

I don't think it much matters if you can't hear the difference. Isn't that the ultimate test? I trust your judgement more than my experience- after all, your ears are in the room. One caveat- don't listen to those who say cables don't matter. They do. Luckily my wife has great ears and can hear the difference too. When I upgraded to Siltech she heard a big difference. The previous upgrade to Synergistic Research had been a big disappointment. A lot has to do with your gear. One nice thing about Audiogon, is that you can try a lot of things cheaply.

I bought a cheap cable from Best Buy for my Stadium IIIs and replaced my Cardas Hexlink with it. I didn't hear any difference in the sub. Sold the Hexlink and pocketed the difference. On the other hand, I went from Cardas NR to Nirvana X-S between my preamp and amps and noticed a large difference.