Im not sure what makes these speakers work better on a long wall than the short. Its just how they were designed. I own the Dunlavy IVa, and owned the IIIs prior to that. They work on the short wall, but not as well as the long wall. Dunlavy as well as Audio Physics are designed to be put as far apart as possible with a large amount of toe-in. they still require thought on placement from the wall (distance into the room) and work best at 1/3 distance into the room like other speakers. They also work at 1/5 or 1/7 points (distance is measured from tweeter back through speaker to wall) the distance to the side wall needs to be at least 1/3 more or less than the back wall dimension. In your case with one side open I would make the other side 1/3 greater than the measurement to the front wall.
So given your room (15x12.5) the speaker if set-up 1/5 into the room would be 2.5 into the room (tweeter to wall) and the left speaker will be 3.4 from the side wall (min.) It is recommended to have the speakers 8 apart (this can be less, but your ear must be no closer than 8 to the tweeter to keep the time coherence correct) but something less can work. The couch on the back wall with an absorbent material on the back wall should work fine; in fact this is how I have seen two showrooms (one for Dunlavy and one for Audio Physics) laid out. I should mention Dunlavy is no longer made, but they are excellent speakers still.
The biggest down side of the speakers being placed this close to the front wall is a loss of soundstage depth. You can increase the apparent soundstage depth by using a highly absorbent material on the front wall. The TV is an issue, so you may need to keep the speakers at the 1/3 point like you have them now. TVs and two channel are tough, this may remain an issue???
One major downside of this type of speaker placement is the size of the sweet-spot. This layout tends to favor a single listener for perfect imaging, but this is not to say you both will not enjoy.
If you want to discuss this further, send me an email and I can send you my phone number
jade
So given your room (15x12.5) the speaker if set-up 1/5 into the room would be 2.5 into the room (tweeter to wall) and the left speaker will be 3.4 from the side wall (min.) It is recommended to have the speakers 8 apart (this can be less, but your ear must be no closer than 8 to the tweeter to keep the time coherence correct) but something less can work. The couch on the back wall with an absorbent material on the back wall should work fine; in fact this is how I have seen two showrooms (one for Dunlavy and one for Audio Physics) laid out. I should mention Dunlavy is no longer made, but they are excellent speakers still.
The biggest down side of the speakers being placed this close to the front wall is a loss of soundstage depth. You can increase the apparent soundstage depth by using a highly absorbent material on the front wall. The TV is an issue, so you may need to keep the speakers at the 1/3 point like you have them now. TVs and two channel are tough, this may remain an issue???
One major downside of this type of speaker placement is the size of the sweet-spot. This layout tends to favor a single listener for perfect imaging, but this is not to say you both will not enjoy.
If you want to discuss this further, send me an email and I can send you my phone number
jade