What is stereo imaging?

[Diffusion]

Im not a newbie or nothing, but lately I heard a lot of people talking about stereo imaging... What exactly is stereo imaging? Also, what does it mean for monitors to be "out of phase"?

[mshilarious]

Originally Posted by Diffusion

Im not a newbie or nothing, but lately I heard a lot of people talking about stereo imaging... What exactly is stereo imaging? Also, what does it mean for monitors to be "out of phase"?

It's basically how realistic a stereo image is created, either by a mix, or a pair of monitors. If stereo monitors are "out of phase", it probably means one of two things: the stereo image of a mix is so exaggerated that the left and right channels are carrying opposite or somewhat opposite signals. That might sound cool on headphones, but in a mono mix large chunks of the sound might disappear

Or more simply, it might be because the monitors have reversed polarity, because the speakers leads were swapped on one speaker.

[gecko zzed]

1 stereo imaging in recording is essentially about placing an audio signal somewhere between the left and right speaker, where this placement is determined by the 'pan' control. One of the arts of mixing is being able to use all the space between left and right in an acoutically satisfying and sound way through the skilled placement of all the audio signals that make up a song (including the derived signals such as reverb).

2 Speakers work by pushing air. If speakers are connected 'in phase', it means that both, on receiving a signal, push together. They are connected in phase when the positive output of amp is connected to positive input of speaker. If the speakers are 'out of phase', when they receive a signal, one will push, and the other will pull. The effect is that they tend to cancel each other, resulting in loss of volume. This happens when positive output of amp is connected to positive input of one speaker, while positive output of amp is connected to negative input of the other speaker. This can easily occur if the speaker cables are wired incorrectly.

[whjr15]

damn good explination gecko ... i had no idea exactly what "out of phase" was, other than it being a bad thing

[LOUD1]

I found this definition of Stereo Imaging on the web:
"The production of stable, specific phantom images of correct localization and width."
I always thought it was the relative positio of an instrument or voice sitting in the mix.
Regarding "out of phase" - That would be when the stereo monitors are wired backward with respect to each other. For example: one speaker having the + and - corresponding to the + and - of the amplifier and the other channels speaker wired reverse where the + from the amplifier is connected to the - of the speaker and the - of the amplifier is wired to the + of the speaker. The sound produced by the speakers would be out of phase. The cones of the speakers would be moving air in opposite directions. One speaker would be moving air forward while the cones of the other speaker would be moving in the opposite direction. This would cause phase cancellation creating at best very poor sound quality and at worst loss of sound where equal sounds (amplitude and frequency) of opposite phase would cancel each other out. This is the principle used in the noise cancelling headphones where they amplify the surrounding sound and invert it in the headphones to cancel the loud surrounding noise.
I hope this helps answer your question.

[bennychico11]

not to get into semantics or anything...'cause I know a couple of guys who are going to jump all over my ass for this
but mshilarious' definition of "out of phase" speakers is closer to the actual interpretation.

quickly:
Switching the leads on a speaker will mean that one has had its polarity reversed from the other one. In other words, the + of a waveform is now -

Phase is a proponent of time. It relates to where the waveform is at in its current point in time. A change in the phase is equivalent to a shift in time.

Two speakers being out of phase with eachother is similar to two microphones being out of phase. If one of the speakers is further back from your ears, then the sound will arrive later than the one that is closer.

[gecko zzed]

mshilarious and bennychico are exactly right. I wasn't too sure about how complicated to delve into the topic. Being 'out-of-phase' has only one point of reference, which is when the sound hits your ears. Reversing polarity is a mechanical way of getting something out of phase, and is a very common way of doing it, but, as you say, if the distance from each speaker to your ear is different, by the time it gets there (at least for some of the wave lengths) it will be back in phase.

In a recording situation, out-of-phase problems can occur with mike placement, in which case they are embedded in the recorded material.

[rayc]

Diffusion,
Quite a few CD lense cleaners have bonus tracks on them for L & R separation, phase test etc. VERY handy & something that SHOULD be used every time you connect some new stereo gear to the rig OR make changes.
Oh, by the way a compressed, diffused sound is an indicator of phase problems.
Cheers
rayC