Read this: https://www.passlabs.com/technical_article/speaker-cables-science-or-snake-oil/
Ideally, one wants to use short speaker cable lengths, but 20ft is not going to murder your system, and certainly not in comparison to acoustic distortions from reflections and room modes. Treat the room. Get the right speakers for your placement restrictions, sonic preferences, and room size.
All speaker cable degrades through loss of high level signal, and more so when running into a passive crossover where it can interact with the filter responses. In pro audio, they prefer to use active speakers so no passive crossovers, and no speaker cable rather than long, balanced interconnects, which are better for long runs being low level signals.
Ideally, one wants to use short speaker cable lengths, but 20ft is not going to murder your system, and certainly not in comparison to acoustic distortions from reflections and room modes. Treat the room. Get the right speakers for your placement restrictions, sonic preferences, and room size.
All speaker cable degrades through loss of high level signal, and more so when running into a passive crossover where it can interact with the filter responses. In pro audio, they prefer to use active speakers so no passive crossovers, and no speaker cable rather than long, balanced interconnects, which are better for long runs being low level signals.