Having an imperfectly shaped room is NOT the end of the world. There are much worse things, like death, taxes, world hunger and being stuck listening to only headphones. If the latter were the only option I'd sell my gear as there'd be no reason to own it.
There's more to acheiving good sound than having two pairs of parallel walls (which I do have, btw...and then some). Though maybe not perfect, this L-shaped room does not "suck" nearly as bad as the previous, rectangular one in my old house. The new one has more floor space (speakers well away from all the walls) and higher ceilings, thus more room to set up and breathe. It has almost no slap echo (sprayed cathedral ceilings) and the floor is a carpeted, padded slab rather than a raised wooden floor (no booming resonance). The electrical system is more modern, too (cleaner, more consistent power). Oh, and the windows don't rattle in their frames, either. ;-)
The current set up, which is down the long leg of the "L", is also better in many respects than the first try here which was in near field on the long wall. That was OK, being very detailed and accurate overall, but there was a lack of ambient space and realness to the music. It simply wasn't musical. That set up was also greatly influenced by the bass accumulation in the outside corner of the "L".
Interestingly, the current set up looks like it will be very near to what the Cardas Method formula would have indicated had the long leg of the "L" been a singular room. The distance from the front wall is as the formula prescribes, the distance from the side wall is increased by 1.5 and the speaker on the open side is positioned where the formula suggests were it a rectangular room.
The keys were deciding which end to use as the front wall and where to put the listener position. The software referenced above helped with all the "what if" scenarios, thus aiding in determining where to start. Even with it there was still a lot of physical experimentation, further tweaking of the model, then actually trying the output, etc. The software is not a cure, but it is surprisingly accurate which sped up the entire process of finding the best possible positions for everything. Getting visual input supported by audio cues, and vice versa, is a powerful combination.
As set up the sound is already *considerably* more balanced and holographic than in the previous room or the referenced near field set up, even without *any* acoustic treatement. The frequency response is fairly flat with one hump of 4-5 db at the lower end of the speakers' useable range; all other fluctuations in total sound are less. That's out of the box with a well planned set up. But there's still work to be done.
Both speakers are 5.5 feet from the front wall, 7.5 feet apart and the left one is what some might call "in the middle of the floor". Ultimately, slightly assymetric positioning from the front wall might be necessary, but I'm trying to avoid that to keep the direct sound time aligned. So far with seeming success.
The first major issue to tackle will be dampening the wall on the right. It is currently untreated, with the speaker well away from it (4 feet). A wool rug will be hung here at a minimum. Then there's the bass issue; resonators may be preferable here due to the concentration and localization of the bass energy. Need to research that a bit more.
Where I played the most games was the listener position. The best spot is centered in the long leg of the "L", just behind its inside corner. This puts the corner at the point of first reflection, but also largely cuts off the influence of the other leg of the "L" from the listener. Thus, there is some reflected sound to balance with the right side and the other leg has a lesser effect than in a more forward position. This position also puts the listener centered between the apex of the cathedral ceiling and the drop down ceiling to the rear. This is 12.5 feet from the front wall and 7 from the rear one. That the slope of the ceiling is assymetric, the long slope being down toward the front wall seems to have a positive effect. Reversing the room was not a viable option sonically or decor-wise.
Perfect? No, but achieving that would assuredly entail building a custom home and I am doomed to being a renter in the San Francisco Bay Area. Is this set up a reasonable one for everyone? No, I'm single and have the luxury of spreading out as desired. Can't imagine that most wives would go for the position of the left speaker. They might in a pinch; but it's close to "in the way, honey". In any case, it's not in MY way. I did try it further to the right which was OK, but things start to get compressed when my speakers (Hales) are much closer than 6' apart.
So, don't give up on a room just because the books say it's not perfect. A lot of reading material say cables shouldn't make a difference and we know better, don't we? Use the best tools available to work with what you've got. The results can be quite surprising.