I recently purchased an SW-15 II powered sub to compliment my Heresy II's in my home theater.  The problem I'm having is connecting it to my Sony STR-DE825 receiver (100w/ch x 5.1).  The receiver has two "Sub Outputs", if I connect my Monster Sub Cable from one Receiver sub output to either Left or Right Side low level inputs on the sub, it seems to work fine (Note: however I do have to crank the volume of the sub up to 8-10 to get decent volume).  Therefore, even this setup seems to not be 100% because I would assume that with the size of the SW-15 II it should take much volume at all to really feel the effects of the massive 15" woofer/passive radiator).  However, the real issue is if I attempt to split or "Y" the input signal as I've read about to add approx. 6db, I get a very loud thud when the center pin of the RCA cable touches the other low level input and then the sub will not put out any sound at any volume.  Could this be caused by my receiver not putting out enough signal to drive both inputs or is there an underlying problem with the subs amp??

Also, when I attempted to use the high level speaker inputs to see if they would perform any better, all I got was a constant hum????

Any help from the more experienced Klipsch Sub owners would be greatly appreciated.  Happy Holidays and Happy New Year! 

 Or Should I give up and get a KSW-15 instead??  

I had a similar problem with my SW-15 although my setup is quite different. Try this. With everything powered down, connect the Y-splitter to the input of the SW-15, and run the single end to the OTHER sub out on the sony. Now LEAVE THE SUB OFF and get into the sony menus; make sure to set the LFE all the way up to "0 DB" and make sure it is not set to "Muted". Also make sure that the Sub is set to "Yes." There are separate LFE level, Subwoofer level, and Sub yes/no adjustments on this receiver. Put the SW-15 gain up to halfway and set your speakers in the Sony to "Small." Stay in the Sony's menu system and start with the Subwoofer level in the Sony at "0 DB", NOW TURN THE SUB ON and go up or down from there adjusting the level by exiting the menu and playing some material with good bass. You may have to adjust the receiver subwoofer level, and the sub gain on the SW-15 again; but this should get you some good, workable results. I'm running analog outs from a Sony S550 bluray player through the multichannel input of a Chiro C-800 and I had to set the Sony to small to get redirected bass to the sub on anything that had no LFE channel in the mix. If the sub doesn't work with the above procedure, I would say you have an amp issue. The SW-15 is more than powerful enough to rattle the walls! You might want to upgrade your receiver if you want a more sophisticated bass management set-up since the Heresys are probably not being fully utilized by the small setting in the Sony. Good Luck and Merry Christmas! P.S. Also keep an eye out for a blown fuse.