Finally! The end of a long road to speaker placement

[Varun]

Hi everyone,
A few months ago I had my sl3's perfectly placed, and sounding amazing. The soundstage was ginormous and imaging was laser-pointer accurate. Then I moved the speakers to make room for a projector. A month later I put them back, but the soundstage is completely gone, the speakers sound terrible.

So these past couple of months I've been fiddling around with the placement, moving my sound absorbers and diffusers everywhere trying to get it right, still nothing. Then today I check the polarity the cables, turns out the high frequency was backwards on one of the speakers. I flipped it and now I'm back to audio nirvana!:rocker:

Why didn't I check this earlier? I have no idea, but the reason for this post is the interesting effect that flipping the polarity had.

Sounds that normally came from center came from the sides of the speakers. Now, this didn't apply to all the sounds, only those that normally came from beyond the separation width of the speakers.

So I guess I have 2 questions, can any technically savvy person tell me how stereo speakers can create sounds that seem to originate outside the speaker separation width? This seems kind of magical to me.

Secondly, why would flipping the polarity on 1 speaker change the origin of only the sounds that seem like their coming outside the speakers' periphery? I'm referring to the case where the soundstage extends beyond the speakers' separation. I'm only able to achieve this effect with proper placement of my bass traps and diffusers.

I've read numerous articles on room acoustics and speaker placement, but I've never come across something that explains this phenomenon.

Thanks!

 

[Wickfut]

So I guess I have 2 questions, can any technically savvy person tell me how stereo speakers can create sounds that seem to originate outside the speaker separation width? This seems kind of magical to me.

While the panels are in phase then the sound comes from further than the speakers as an effect of the room. The reflection off side walls and ceiling/floors mix with the direct sound and feeds your brain with false spatial information.

Also you can simulate this effect in the recording by using doppler effects (slight delays either left or right side sounds) ... Roger Waters - Amused To Death shows this effect off really well.

Secondly, why would flipping the polarity on 1 speaker change the origin of only the sounds that seem like their coming outside the speakers' periphery? I'm referring to the case where the soundstage extends beyond the speakers' separation. I'm only able to achieve this effect with proper placement of my bass traps and diffusers.

While they are out of phase, the direct sound from each speaker cancel each other out so you hear the effects of the room more.

Some TV surround processors use this "out of phase" effect to give you a psuedo surround sound from 2 speakers.

Hope that helps.