That is interesting. What disc is it? What are the output settings of the Sony player? What sound mode was used for playback in the 7706?
7.1 analog for playback. That is what the 7706 says, but as you know SACD actually only supports 5.1. So the disc is actually playing in 5.1. The disc is from the complete Beethoven symphony set under Osmo Vanska with the Minnesota orchestra, recorded by the Swedish BIS label. This is from the time, when the UK Gramophone magazine awarded the Minnesota the title of Orchestra of the Year. It is an absolutely outstanding Beethoven symphony set. This disc is BIS SACD-1416.
These discs I know are mixed 5.1 but with the surround in the rear position not the side.
If you play the disc via HDMI then the rear become the sides. However I don't think this accounts entirely for the improvement in that in the 7.1 analog I have set to the three fronts the rears and the sub channel. May be these receiver DSD decoders are a bit io an afterthought as SACD is a dying format, if not dead. The fact is that it should never have seen the light of day. We have the Audiophools to thank for that, with their total misunderstanding of PCM. But that is another story.
My side speakers are my old location monitors from my radio broadcast days. They date 1984. They are really good speakers. The musicians would gather in the room to have a listen after the concert. Some of them were persistently trying to buy those speakers from me.
The rear backs have the longest genesis of any speaker I designed. The design was started in 1976. I would say it was about 13 to 14 years before I was really happy with them. We had an impromptu music club in Grand Forks and would go to each others homes. In the end they decided to always use my basement. Bob Carver came to Grand Forks to personally deliver and set up a set of his hybrid Ribbons ordered by one of our cardiologists. The cardiologist told him he had to those speakers now in the back of my room. He came on a Saturday afternoon and just loved those speakers. I thought he would never leave!
So those rear surrounds are way overkill, but the side surrounds are can also hold their own. So it must be optimal to have the speakers in the right place.
The recording companies are really reluctant to make demands on any speakers other than the front three and subs. I would really love to have some good antiphonal discs of Italian Renaissance antiphonal music to illustrate the possible. The fact that a prominent reviewer stated that Aho disc was unplayable did not help.
