another stock stereo question..

[Vinman]

does anyone know what kind of crossovers are the stock ones (at least thats what i think they are..they're in the wire that i think goes from the tweeter to the 4x6, its hard to explain i'll put a pic up later). what happened is that i accidently cut the one on the passenger door off, and now..6 months later...the pass. door speaker is pretty much junk( mind you its a brand new pioneer..er 6month old pioneer)...and yes i spliced the wires back together like nothing happened

What would be a good replacement to just do a mild stereo upgrade?..I.E..new 6x9's in back (done) new door speakers(was done, but am re-doing), maybe new tweeters(don't know if i really want to do the cutting just yet), and new h/u...

Are having these "crossovers" really that crucial for a basic stereo?

thanks