Im building an enclosure for 2 12 BLs with 2500w RMS and I want to put a window in the back, Im not sure what the best material to use is, Ive heard different things but it seems my two options are 3/4inch Plexiglass or 1/2inch Lexan... Which is better?

lexan is strong stuff. i would go with that if you can afford it. its close to bullet proof IIRC.

Given the thicknesses of both materials, either would work fine.

How big is the window going to be?

The window is gonna be 12x24... I cant seem to find 3/4 inch Lexan but 3/4 Plexi is around the same price as 1/2 in Lexan so im up in the air still

For a window that big I would personally go with the 3/4" plexi.

once you get to 1/2" or greater, plexi is pretty damn strong, at 3/4", that should work out quite nicely, just do us a favor and post some pics when it's all done would love to see it!

Plexi won't scratch as easlily as the Lexan will Its harder. Lexan is more flexible , which helps with its bullet resistance.