That's an intriguing idea. I didn't realize that the back surrounds could/should be that close together. If I were to go with the 7.1 option, I'd buy a pair of di- or bi-poles for the side surrounds and move the current surrounds to the back surround position. These speakers are rear-ported, so is distance from the back wall going to be an issue?
With rear ported speakers, it is always a good idea to leave "breathing room" behind them. You are correct, however, that this matters less when using bass management to remove the bass to them, but it would still be best to allow some room behind them.
Or, by crossing them over at 80Hz, will that reduce or eliminate any concerns about exaggerating the bass output.
I am concerned about the height though. By "2 feet above seated ear height", are you using the tweeter as the reference point?
Obviously, I cannot say what he meant, but the tweeter is the standard reference point on a speaker for determining height.
I would think that the further away from the listening postion you place any particular speaker, the less important the height becomes. Would that be accurate?
Yes. You still don't want anything physically between you blocking the sound, so above is generally a good idea anyway.
The height placement will definitely be an issue. Since that section of wall is between 2 doors, it is a traffic area. I have visions of heads bashing on the speakers or the shelf. So, if I put a shelf there, I would prefer to put it at 6 feet. I'm the tallest in the house, at 5'8", so that should be safe. However, the tweeters would then be quite high - 40 or 41 inches above seated ear height and only a few inches from the ceiling.
The further away it is, the less it will matter. What sort of distance are we talking about?
Finally, that section of wall is 30" wide and off-centre by about 18", i.e. 58" from one side wall to the far edge of one door opening and 40" from the other side wall to the far edge of the other door opening (Hope you can picture what I'm trying to say). At 12 feet from the back of the couch, would being off-centre by that amount be an issue? I wouldn't think so, but opinions are welcome.
I would try to get it as close to centered as possible, though the rear matters far less than the front (see below). I would not place the speakers next to the doorways, but spaced with reference to the seating position, insofar as that is possible. In other words, I would probably place one of the speakers next to the doorway, and the other one 18" away from the other doorway (due to the 18" off center of the space; I hope you can tell what I mean by this).
I appreciate anybody's input.
So, is it worthwhile to go the 7.1 route - or stick with 5.1?
Only you can decide if it is "worth it" or not. In most cases, 6.1 or 7.1 is not a dramatic improvement over 5.1. There are many reasons for this, which depends upon speaker placement, the fact that humans hear better in front of them than behind them, many movies are only recorded in 5.1, and even those that do have 7.1, the sound in the front is the most important part of the soundtrack anyway. When I went from 5.1 to 6.1, I was underwhelmed by the difference. I now have a 7.1 receiver, and I already have the speaker to add for 7.1 sound, but I have not bothered to add the speaker, so I am still running 6.1. If my speaker placement options were better than they are, I would go 7.1 (because I already own all I need to do this), but it really is fairly trivial.
Obviously, when placing speakers and such, you must deal with what is possible in your space. Something less than absolutely perfect can still sound quite good, so I would not let slight imperfections in placement bother me too much, particularly when dealing with surrounds.
