Believe it or not, front- or rear-mounting a speaker on the cabinet baffle can make a difference to your tone. There is a lively debate surrounding how big a difference this actually makes, and the amount can vary depending on whether the cab has an open or closed back, as well as the thickness of the baffle itself.
We can see this from the frequency response measurement shown. The blue curve shows the response of the speaker mounted at the rear of the baffle, and the red curve shows front mounting. The difference is noticeable.
Tonally, front-mounted speakers will exhibit greater clarity and sound a little more open and neutral—attributes that are particularly beneficial for clean tones. For the rear-mounted speaker, the baffle creates a subtle horn effect that boosts the lower mids while making the speaker sound darker off-axis. Additionally, the “acoustic mass” of the air cavity shifts the overall tonal balance for a further perceived midrange boost. This can be beneficial if you need to beef up high-gain amp sounds.