What are good ratios for cold brewing coffee?

I’m using a mason jar + inserted filter method to brew cold brew concentrate. My normal method is 2L water per 110 grams of coffee, left in the fridge for 24 to 48 hours. Is this good for a concentrate or should I adjust my ratios/time/temperature? I’ve heard that room temperature is better, but I haven’t seen anything to back that up. Seems like it would be better to maintain lower temp for bacteria. Any advice?