Long Wall Speaker Placement: Pros and Cons?

There have been a few threads on tweaking speaker placement for imaging etc, but (at least for Magneplanars) it seems most people position them on the short wall firing down the longest dimension of the room.

Decorating and architectural considerations will now be moving my Tympanis to the LONG wall of my rectangular room (approx 18 x 25) where they will be firing across the 18' dimension of the room.

I am imagining - just a guess - that the bass response will suffer in this move which is a concern. Also, this will make it trickier to bring them out 3 feet or more from the new "rear" wall.

However, I suppose this might make it easier to move the speakers farther apart which could enhance the width of the image?

Or offer some other benefits from sitting several feet closer to the panels?

I really hope I can get them to work well this way and would appreciate any insights or advice.
While I have never owned planars, I prefer long wall placement. I suspect that your bass resonse will actualy improve. Having greater distance from side wall reflections may improve clarity. My only suggestion is to place some foam padding to aborb refletions from the wall behind the listening position. You can hide the foam with a decorative wool covering. Be generous with this room treatment and you may be able to sit further back and maintain a nice distance between speakers and the wall behind them. Good luck, you may be in for a pleasant surprise.
They'll work. You may need something behind those speakers to damp the rear wave of them. I had maggies years ago with this placement. Check my system pics, my Wilson's are on the long wall now. My audio buddies say it sounds pretty darn good, in fact one, with a much more (and frankly better) expensive system loves my bass.

Just play with it. Good luck !
Audio Physic always used to be a big proponent of long wall placement (and prob'ly still is). They had a very detailed mathematical procedure for optimizing sound in a long wall placement. Check out their website, they may still have info on how to set this up properly. I have heard their Virgos set up like this, and it is truly spectacular, some of the best sound I have ever heard. I heard home theater in another shop that had a very modest system set up on a long wall, with a large space between the speekers and the side walls. It presented one of the most spectacular (in a subtle realistic way, rather than in an obvious, overdone way, which is waht made it so spectacular) sense of spaciousness I have ever heard. I envy you, as my room dictates a short wall placement, and my sound stage suffers for it. I think you are in for a pl;easant surprise!!!
Con: looks weird.
I have had AP Virgo's set up on the long wall for several years and they sound great. Definitly go to AP website, their long wall set up instructions will be helpful.
since your speakers are dipoles, they have a very unique output pattern...front & rear (figure 8 pattern) and no output to the sides... dipoles can be placed very, very close to a side wall..front / back wall setup is critical..
Mikesinger and others

I need to read the audio physic text again on placement.

It all seems very interesting, but would you say it is not appropriate for dipoles?
i dont think it would be...
I have the same situation as your room layout...I tried placing my speakers on the short wall of the room but never liked their sound as much as I do having them placed on the long wall now...The bass from the subwoofer is impressive especially after some wall acoustic treatment...
Unsound and others

I finally got everything moved to the long wall yesterday.

Good news -- even before dialing the panels into tweaked position, I can tell it is going to sound just fine and probably even better. This is a real news flash for me after 20 years of putting Maggies on the short wall.

My listening chair is closer, the speakers are farther apart, and I am using a bit more toe-in to adjust for the width.

So far, the imaging seems very good, the bass is initially less impressive but actually just less boomy, and everything sounds much more pulled together and coherent.

They are only about 2ish feet out from the rear wall, however, which may be hindering front to back depth.

Will report any interesting observations and try to update my system photos soon.

Thank you.
Cwlondon, thanks for the update. I always appreciate it when those who pose a question respond with their decision/results. I don't know about your room and living requirements, but, if you can move your seating position as far back as possible (say about a foot from the rear wall), use the room treatment I've previously suggested (for different reasons than I'm about to discuss) and move your speakers out from the wall behind them (perhaps, for a total of 3'). I think you will achieve the best possible bass response. Let us know what you do. Good luck!