NOT TRUE... A Larger sealed box will give a much warmer, true sound. Look up the SQ specs on many subs, the bigger the better(within reason) You are trying to tune the resonant frequency of your box to the sub. Smaller is NOT better, this is why when you use a small enclosure you're told to use polyfill, to increase the apparent size of the enclosure, but also to add some dampening to smooth out the response. Also a larger box will be more efficient. Also angles? where does this come from. angles cause refelections which will cause standing waves, which will in turn will degrade sound quality, also you may have phase issues doing this. If you mean angles on a port, such as a folded horn design enclosure you had better know what you are doing before you even start, arbitrarily adding angles to your box will do nothing but cause trouble.

Also it depends on what you are looking for. If you're looking for SPL(which I was) a large tuned box is you key. If you're looking for a very warm sound in your car, a large sealed box is for you. If you are worried about size, then go small, but be forwarned, while midbass extension is great in small sealed boxes, they won't cover the entire gammut of "bass"