I’m in process of rebuilding the crossovers in my 70’s vintage advents. For years i had monster cable from my maranta 2230 to speakers. When i opened up speakers the wiring from speaker connections to crossover and speakers is 20 gauge wire. I’m looking at this and thinking why have such heavy cable especially since I’m running about 10 ft. Started reading people opinion on strand vs solid and was curious about other folks results. I realize these are not 10000 dollar speakers
The effect of the wire gauge is directly proportional to its length, so.....
When your equipment was new, most stereo stores gave and sold 18 ga speaker wire, up to about 30 feet and if it was a longer run/higher power, it was 16 ga. There was no 12ga speaker wire unless they just wanted to make more money, there was no star quad, no cables with batteries, cable pants and the speakers didn't have binding posts, so banana plugs weren't gonna happen. Even brands that are seen as 'classic' and collectible didn't have much more than terminals with spring clips.
Also, crossovers don't usually need to be rebuilt because the caps are mostly non-polar and most aren't electrolytic. High voltage electrolytics in tube equipment, mainly amplifiers, need to be replaced when they sat for long periods or just failed, but it's OK to leave the non-polars in crossovers. The coils and resistors don't go bad and if you replace the components, it will likely change the sound of your speakers in ways that you can't predict and might not like.
Read Roger Russel's article on wiring.