I have basically the same problem with an onkyo 609 and acoustech pl-76/pl-26.. I got these as a cheaper alternative to klipsch heh. I posted in my speaker owner thread but maybe this will get more attention:
I noticed there's slight hissing with slight crackle, especially from the center.. I can barely hear it but when I put my ear near the center I can hear it easily.. it happens even when I turn off my source(mac mini) and my projector.. I tried switching to stereo listening mode because that disables the center channel but I could still hear it.. what should I be checking? should I re-run the speaker wire from the receiver to the speakers? it's 18 gauge thin wire that came with my htib. i have my onkyo 609 set to dynamic eq enabled, dynamic volume off, ran audyssey and raised crossovers to 80hz.. thx loudness plus on.. could it be one of these settings?
edit: i have them in a small room and audyssey mostly set the speakers like -7db etc.. would I get less hiss if I changed it to louder.. like 0db.. and then I could turn the volume knob lower with the same amount of actual loudness?
should I buy new speaker cables? I don't hear any hiss from my htib front speakers which I'm now using as rears
edit: just ordered some 12 awg cables from bluejeanscable and some banana plugs.. we'll see if this has any effect
Gear list: Main setup - Kef Q900, Svs sb12-nsd subwoofer, onkyo 609 receiver, epson 8350 projector, elitescreens sable 92" screen, mac mini htpc
bedroom setup: PSB Image B5, maverick tubemagic a1 amplifier, hifimediy sabre9023 dac, ZMF Fostex T50RP modded headphones
preordered gear: Light Harmonic Geek Pulse X dac and headphone amp