Well, you wouldn't be able to secretly insert an out of phase message with this because your ear won't know the difference and would still hear all of the same information from the normal stereo speakers. Also, you only want to use resistors on the audio leads and not the ground. This is because you'll still be subtracting the channels from eachother a bit if the music is in stereo. You must therefore connect the ground directly and the audio lines through medium resistors of about 330 ohms depending on the impedance of headphones.
If any of you know what a hafler matrix is, then you'll know exactly what I've been talking about all along anyhow.
For those who don't, I'll describe it a bit:
In the matrix, the left and right stereo channels are compared to eachother. Only signals that are different in volume or phase between the two channels will come out of the matrix output.
This can be done using a transformer quite easily, or you can use transistors or op amps. When you listen to a hafler matrixed system, there is a speaker in the rear that reproduces the sounds coming from the matrix. Normally you'll hear all this information in a regular two speaker system, but having the subtraction behind you creates a surround sound effect and works very well with some music. This is exactly how Dolby Pro-Logic works, except they have a center channel. When they record movies for dolby prologic, they send the rear channel to both the right and left channels at the same level, except one of them is out of phase. Thus, these sounds appear more at the rear speakers than at the front and give the impression to the listener that the front and rear channels were discreetly recorded.
Now you may wonder how they make the rear channels sound like they're in stereo. Well... This is another elusion created by having some of the rear sound come out of a front speaker to make the rear sound like it's coming from a specific side. As for the center channel, it's just the difference between the front channels in mono and the back channel. Thus, the front speaker only emits information that is common between the stereo channels and anything out of phase or panned slightly is greatly reduced in decibels at the front speaker. This gives an extremely good surround sound picture if the channels are properly balanced and the movie/music was recorded well and balanced.
I made a special Dolby Pro-Logic decoder out of Hammond 850G broadcast quality hybrid interstage transformers and added my own improvements to make each channel sound completely discreet and clean. My own decoder works much better than most pro logic ones you'll ever find at a home theater retailer.
If any of you know what a hafler matrix is, then you'll know exactly what I've been talking about all along anyhow.
For those who don't, I'll describe it a bit:
In the matrix, the left and right stereo channels are compared to eachother. Only signals that are different in volume or phase between the two channels will come out of the matrix output.
This can be done using a transformer quite easily, or you can use transistors or op amps. When you listen to a hafler matrixed system, there is a speaker in the rear that reproduces the sounds coming from the matrix. Normally you'll hear all this information in a regular two speaker system, but having the subtraction behind you creates a surround sound effect and works very well with some music. This is exactly how Dolby Pro-Logic works, except they have a center channel. When they record movies for dolby prologic, they send the rear channel to both the right and left channels at the same level, except one of them is out of phase. Thus, these sounds appear more at the rear speakers than at the front and give the impression to the listener that the front and rear channels were discreetly recorded.
Now you may wonder how they make the rear channels sound like they're in stereo. Well... This is another elusion created by having some of the rear sound come out of a front speaker to make the rear sound like it's coming from a specific side. As for the center channel, it's just the difference between the front channels in mono and the back channel. Thus, the front speaker only emits information that is common between the stereo channels and anything out of phase or panned slightly is greatly reduced in decibels at the front speaker. This gives an extremely good surround sound picture if the channels are properly balanced and the movie/music was recorded well and balanced.
I made a special Dolby Pro-Logic decoder out of Hammond 850G broadcast quality hybrid interstage transformers and added my own improvements to make each channel sound completely discreet and clean. My own decoder works much better than most pro logic ones you'll ever find at a home theater retailer.