Lots of stuff going on with cables that can cause a noticible difference depending on cable construction, length, guage, etc as well as how an individual cable interfaces electrically with the amp and speaker. No easy answer to your question, unless........
You forgot to reinstall the jumpers in your speakers when you connected your single runs. You may not have operative tweeters. Wouldn't that be embarrassing? :-)
You forgot to reinstall the jumpers in your speakers when you connected your single runs. You may not have operative tweeters. Wouldn't that be embarrassing? :-)