Thomas Juth shares a habit he picked up assisting Tony Maserati on a Craig David mix: Maserati kept an old ghetto blaster set up in an awkward spot just to check vocals on it. The reasoning is simple. Most people hear music in a car, an office, or off a small Bluetooth speaker, almost never sitting in front of studio monitors.
He still cross-checks on headphones and big speakers, but treats small, cheap speaker playback as the priority test for vocal decisions, not an afterthought. It's a quick way to catch balance issues that only reveal themselves once you leave the studio bubble.