Spoke to him and explained him - What's wrong with this sentence?

Usually 'speak with' is used for general 'talking', while 'speak to' is more when one person is addressing several others (e.g. 'Teacher speaks to the class') or one person is conveying something specific to another (e.g. "Did you say that he was not helpful ? I will speak to him") where the intent is only one is doing the speaking !


- 'explain x' and 'explain to x' are different : The former 'x' is that thing being explained (e.g. 'I explained Fermat's Last Theorem to my son' or 'I had to explain how I got hold of an iPad on the day of its release') whereas the second 'x' is the person to whom the explanation was given…
 
(From one of my brother's colleague - Radha)