SDA 2 SPEAKERS

I have a set of these they have three meds they have the Chrome two tweeters the 12-in passive radiator on the back they have for the internet interconnection cord they are spades and I thought that they had a fuse on the back connection but these do not have a fuse and I also need to know where I can pick up a set of crossovers or an upgrade for these speakers. I also have a Harman Kardon AVR 520 at 8 ohms and I know I've read that these do get down to 4 Ohms is it possible to run them on the Harman Kardon without any harm done
[ibJimmymac1965[/i]

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