I just think I am meant to be forever slightly confused about this issue. I'll try just listening to the music and not worry too much about it.
biz
Hi, biz,
It's really quite simple and is something you need to know, to get maximum enjoyment out of your music. Let's take the simplest situation, speaker wise, where your speakers each consist of one full-range driver. And I'm talking stereo here, although the same principle applies to multi-channel.
To get a stereo image, you need to have these speakers connected the same relative to each other. Again, let's make 3 simple assumptions:
a) your speaker terminals are coloured 'red' and 'black' - red generally means 'hot' or 'signal' and black means 'earth' or 'return'.
b) your speaker cables also have a red and a black connection (spade, banana plug ... whatever).
c) your amplifier and your speakers have all been built correctly, so wires are soldered to their correct terminals inside the cabinets.
Connecting the R & L speakers "in phase" means:
1. the red cable is connected to the red speaker terminal and the black cable to the black terminal ... for both speakers
OR
2. the red cable is connected to the black speaker terminal and the black cable to the red terminal ... for both speakers.
In both of the above cases, the speakers are "in phase" and you will hear a stereo image firmly anchored between your speakers.
However, if one speaker is reverse connected, compared to the other, you will hear a strangely muffled sound which floats around from side to side and is NOT sirmly positioned between the speakers. This is the "out-of-phase" situation.
The above is the most obvious "phase" issue and is the one most people think of when they hear the term "phase". However, it should really be called "relative phase" - ie. relative to the other channel.
However, there is another issue. Take 1. & 2. above. They are obviously two different ways of connecting the speakers which both keep the correct *relative* phase. However, 2. is reversed from 1.
We would say (all other things in the sound chain being correct) that 1. has the correct "absolute phase" while 2. is "inverted".
What's the implication here? ... if, say, a singer stands in front of you (in the room) and blows, then this sound pressure comes towards your ears. If the singer blows into a microphone, and it's all been recorded correctly, then you should see your speaker drivers moving outwards, towards you, so you experience the same forward pressure coming towards your ears.
If, however, you see the drivers moving backwards, then your system has "inverted polarity". If you think about it, what the speakers are producing is the sound of the singer sucking rather than blowing ... and this has a different sound!
If you think of the leading edge of a transient like a cymbal hit, if your system is showing "inverted absolute phase" (a better term for this is "inverted polarity"), then the cymbal hit will sound very weird!
Unfortunately, many LPs and CDs are not recorded with the correct polarity, so it's hit and miss if you are hearing them "right" or "wrong". That's why it's a boon to have a "polarity reversal" switch - at least you can flick the switch and decide if one way sounds a lot better than the other.
Regards,
Andy
