Learn English – Which one is better in a technical manual: “to obstruct” or “to hinder”

Neither term is more technical. There are certain contexts where there is a difference between the two words. COCA is a good resource for answering such questions in the future. Yes there are objective criteria.

Generally speaking loudspeaker and speaker (in the context of a stereo system) are synonyms. However... I've heard many aficionados use the term loudspeaker pejoratively to indicate the sound quality isn't good enough for them.

The pejorative quality comes from the comparison to speakers used for public announcements. (ie a PA system) Speakers used in PA systems are loud, but otherwise not very good. A corpus search shows that loudspeaker almost always refers to sound systems used by activists, police, firefighters, stadium sports announcers, etc. They are used in public places both outdoors and indoors where loudness is more important that their dynamic range.

I agree with John Lawler. "System shall require customer to take a ticket first in order to enter the highway, and shall not allow customer to enter the highway without taking a ticket first." That is fairly typical specification language.

For those of you not familiar with specification language, typically you use shall to express something mandatory and may to express something that is optional. Using will (as you more likely would in common speech) can be confusing because the fact that something will do something in the future does not clarify whether it is required or optional.