I bought an house which came with a polk audio 5.1 speakers system.
All cable are already in the wall so that's convenient. However the left and right speakers are way too close from each other, especially the surround ones. That makes me think the previous owner didn't know much about 5.1 setups.
The surround speakers are also bigger than the front ones. I wondered if it was a mistake or there was a reason for this?
Size is not the same as quality. Without knowing what they are, it is impossible to tell whether they are better or worse than the ones up front. The better ones, if they are not all the same, should be up front. But the front three should be "voice matched," so if the current three up front all match, and the rear ones don't, then you probably don't want to simply move the rear ones up front, even if they are better. You would want to also replace the center with something that matches them, if you were to move the rear speakers up front and if they are not "voice matched" to the center speaker.
I would try listening to the rear speakers, as if they were just a stereo pair, and listen to the front right and left as if they were just a stereo pair, and decide whether I thought they sounded much different.
If you want more specific help from us, we would have to know what models of speakers we are discussing. As I stated, size is not the same as quality. Usually, though, if the speakers are not the same, the larger ones are put up front. But it is certainly possible that they are all where they should be.
I'm in a similar position, I have 3x cambridge audio x21s 2x cambridge audio x11s and an x301 subwoofer. im planning on putting the 3 x21s up front the two x11s to the side/back.
unfortunately i'm limited on where i can place the sub (apparenlty its a monstrosity, even tho i downgraded it from the x501 for peace and quiet)
The room is this shape.
Will it be okay to put the sub in the top left corner, and do you guys have any recommendations for angle/placement? Also is it best to put the 3 same x21s at the front?
I'd just say to angle the woofer towards the seating position, but you can experiment.
You'll get a flurry of recommendations to upgrade your speakers (they're pretty small for a surround setup and rely heavily on the sub), and sub (you may want more low-frequency for HT).
3 of the same speaker up front isn't a problem.
Can you provide a picture of the setup?
Generally speaking, you want the most capable speakers handling the majority of the work. In a surround setup, the center channel carries the load, then front L/R, then surrounds.
I think that the sub is more important than any speaker except the center. Did the previous owner leave that as well? If so, what model?