I have a Yamaha RX-V1800 and one of its features is that it allows you to run 2 additional speakers mounted above and outside the mains. What they do is add ambiance information derived from Yamaha's DSP functions to simulate the spacial effects of different rooms that Yamaha has recorded. I understand that other receivers offer this same feature.

I tried the DSP both through the main speakers and through the extra presence speakers. The difference is huge and there is no comparison between sending the DSP to the mains as compared to using extra presence speakers. I also compared each to straight feed through the Dolby decoder. Running the 2 extra presence speakers gave me the most bang for the buck, so that will be where I concentrate this post. By running the extra 2 speakers for presence, I loose the ability to run 7.1, which is okay in my case because I don't have the room for those speakers in the back of my room.

The main thing when running in this configuration compared to straight Dolby is that the front wall seems to disappear and the soundstage gets very deep. It's like the screen is sitting in the middle of the soundstage. It also gives more separation to the recorded sounds in a big way. It doesn't seem to change anything coming from the center channel so the voices are still anchored to the screen. When I switch back to Dolby, the room seems to close in and everything sounds dull in comparison.

The more technically minded might point out that sound aberrations might occur from using this feature, but I cannot detect anything worth mentioning. The added spacial imagery is worth the price of admission. Of course, it might be different if your room is huge to begin with, I don't know.

I did show this to several people and all preferred using the extra channels.

So, have you tried it? If so, what is your take on this?