Few questions...
- How are you connecting the source to the 805? (hdmi, optical, analog?)
- What listening mode are you using? (stereo, direct?)
- Do you want your subwoofer to be in the picture for 2-channel listening?
- Audyssey enabled, yes?
I've had the 805 for a little over 3 years. Most of that time I was using somewhat sub-par mains (mid-level vintage 3-ways). During that time I always listened to music in Stereo mode, never Direct or Pure Audio, because I couldn't live without the subwoofer in the picture. I had always assumed that Audyssey was the bee's knees across the board. Thus, Audyssey was always enabled - and in the Stereo mode, Audyssey was working its magic.
Fast forward to this summer. I finally finished my mains. They are plenty capable down to the upper 30's in-room. Suffice to say I spent a lot of time playing around with configurations; sub yes/no, Audyssey on/off, Stereo/Direct, hdmi, analog, etc.
It was quickly evident that Audyssey was crippling the sound with music. With the mains in the receiver set to Large, they send nothing to the subwoofer. With this configuration, I can easily toggle between Stereo mode and Direct. This essentially toggles between Audyssey on and off with just a brief gap in the playback. It was very clear to my ears that Audyssey was NOT improving the sounds - it was making it worse.
After some searching, I discovered that the 805 only has the Audyssey Reference target curve, which is not flat. There are more modern receivers that also have a flat target option, but the 805 does not. Onkyo even names this flat target "Music" and the Audyssey Reference target "Movies" in their such enabled devices. You can read more about that
here and
here.
Try it for yourself and see. If you find a similar result, you have a few options.
If you need a sub, you would need to disable Audyssey (a hassle assuming you like its results for movies, like me). OR use bass management in your source (if it's an option) and send 3 analog signals to the Onkyo in Multich-Direct mode.
If you don't need a sub, just use Direct or Pure Audio mode on the Onkyo.