# Stereo Imaging and Irregular Room Shape



## Twolions (May 21, 2014)

Hi all,

I have done quite a bit of work on ensuring that all drivers are time aligned correctly for the listening position. Phase/polarity looks good too. Measurements seem to be correct and are easily verifiable in REW/HolmImpulse. With that said, I have an odd issue due to the shape of my listening room. To quickly explain - when looking from the listening position to the speakers, the first third of the room has a large hallway on the left side (15m length) and a wall on the right side spawning the entire length of the room. Acoustically this makes it so that when aligning all drivers correctly the imaging is simply off. The position of the instruments is off, the coherence of the sound stage, etc. 

The way I (subjectively) correct this is that I add a 0.4-0.6ms delay for all speakers on the right side (where the wall is) and this (for some reason) greatly improves the imaging. When measurement mic is placed at the listening position (which is in the middle between the left and right speakers - some 3.5m away), both REW and HolmImpulse are showing that the sound arriving from the right is delayed by 0.4-0.6ms. So in some ways it may seem counterintuitive to me that delaying one side's arrival time (the right side) corrects the stereo imaging. My assumption is that the hallway to the left has something to do with it.

I was wondering if anyone has an idea why this is so.


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## bpape (Sep 14, 2006)

The asymmetry is providing more, stronger, quicker reflections from the right hand side than from the hall side. Trying to address that with phase will 'fix' it in some ways but cause other issues. The best way to address it is to damp the reflections on both sides as you can to minimize the differences in reflections/lack of reflections.


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## Twolions (May 21, 2014)

Hi, thanks for the response Bryan. In your opinion would it be better to treat the right wall with diffusors or absorbers?


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## bpape (Sep 14, 2006)

If there are essentially no reflections on the hall side, I would absorb the right side.


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