Best way to hook up dual sub-woofers


I recently purchased 2 NIB PSW505s by Polk audio at a ridiculuos low price and would like to know which is the best way to use both subs with my Onkyo 876. Do I need an external cross-over or the Y spitter would do the jobs?
andrewdoan
I've found the best way to connect subs is using speaker-level connections if the subs allow for it.
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Dave, good info. Thank you. Off the topics, I have listened to my friend's Duetta and they were hook up with a Classe amp with AR pre. I could actually SEE the music. The Apogee is amazing with properly set up.