Here is my issue: I recently re-setup my studio so its shooting the long way down the room pictured here: http://www.goldphoenix.9k.com/Studio.html

I calibrated my speakers with pink noise played through one at a time so that -20dBFS pink noise comes out at 82dBc on each speaker.

The issue is that the stereo image is off...to the left to be exact and everything panned C seems like its coming slightly from more to the left. If I raise the output of my amp's right channel TWO clicks then the phantom image moves perfectly C. However this is not the calibrated levels.

I've measured the distance to the speakers from my ears and it forms the equilateral triangle to within one inch.

I'm guessing its some sort of room mode thats causing a null at the listening position comb filtering?? I just can't figure it out and was looking for some input.

'04 Tony Iommi Signature SG
'66 Harmony Bobkat
Is the room set up how you have it pictured now? If so, straight away I notice you're boxed in towards one corner - that will typically make the speaker nearer the corner's low end more pronounced and boomier, which in turn may be making you hear the left speaker as brighter, and psycho-acoustically hearing the left speaker to be wider out and thus the image shifts to the left slightly.

If not, then do your monitors have an oboard EQ? Perhaps this is colouring the sound in a similar way to above?

Also, worth noting that for a few hours into a project a couple of years back, I suddenly noticed my stereo image was off and the right-hand side sounded a lot duller and bassier... after a few tests with songs I knew well, I discovered that the tweeter wasn't performing properly - to be precise, I couldn't hear anything coming from the tweeter. Turns out a capacitor blew in the circuit leading to the tweeter, effectively cutting it out of the circuit, so one (free, as the speakers were months old and in warranty) repair later and the issue was solved.

Then a couple of months back, in my current place, I noticed a similar sensation though not as pronounced, so fearing for the worst I dug out the receipt... anyway, before giving the store a call I decided to check the speakers over myself a little - turned out that while positioning the speakers how I wanted them to be, the EQ on the back had mysteriously been tweaked and the left speaker was brighter, creating the illusion I described above... I still have my suspicions the EQ was moved by my girlfriend trying to find the switch at the back to turn the monitors on, but hey, I can't be too mad really - she's even learned to call my interface 'the Duet', which was a big step up from 'the shiny box thing' (oh, how I love her)
Hey, look. Sigs are back.
Thanks for the response, I will shift the speakers to the left, and no there is no EQ on board the speakers are passive.
'04 Tony Iommi Signature SG
'66 Harmony Bobkat
Also consider something simple... is your master fader accidentally panned slightly?

Could I get some more talent in the monitors, please?

I know it sounds crazy, but try to learn to inhale your voice. www.thebelcantotechnique.com

Chris is the king of relating music things to other objects in real life.
thanks guys, I found the root of the problem though, it was something simple, as I listened to headphones while music was playing through the mixer, I noticed that with all the faders down except the masters I could hear the bleed between the channels still and I noticed that the left channel was louder than the right channel so I adjusted the outputs of my compressor (which runs in parallel through the board on all playback channels except my DAW) and now I have a good stereo image.
'04 Tony Iommi Signature SG
'66 Harmony Bobkat