"Market maker" is quite a specific term and is typically used to describe companies providing liquidity in a market for a given good/asset/etc. They are almost by definition not speculating, they are in the business of liquidity, and are compensated for providing liquidity.
Speculators would (try to) buy low and sell high, whereas a market maker could well buy high (when speculators are trying to sell) and sell low (when speculators are buying). That sounds counter intuitive, but of course speculators aren't always right, and market makers typically aren't holding assets for enough time for prices to move much, and they make money off a small spread.