Since I have been here I have noticed that the word "compression" comes up a lot. It's like compression has been linked to distortion, so it's probably a good idea to start talking about this because compression comes in a few forms as well as distortion.
You could take the approach that because compression is changing the audio signal from it's original state, this makes compression a form of distortion. However if you go this far, you would also have to say that microphone pickup patterns are also a form of distortion.
I prefer to look at distortion from a more practical view point. My view of distortion is any time the oscillating patterns in energy go out of tune. This makes it a little easier for us in this hobby because we know what happens when instruments go out of tune, but this same thing happens with equipment, rooms, speakers, along with anything in the audio pathway.
the sound of distortion
It's important to know the sound of distortion, or should I say sounds. In this hobby a lot of guys pull out the distortion flag without knowing the cause or what it even sounds like. For example they will claim that a recording is distorting when it is actually their play back system. Along with this we need to take a look at system compression vs recording compression. If you have a system playing a recording that is 30'x30'x12' in size and the system is playing it back at 12'x4'x7' this is system compression not recording compression. Recording compression (limiting) brings the middle dynamics up to meet the extremes, and many times cuts the tops of the extremes so that the music is easier to play. On a piece of vinyl you want the lows chopped so the grooves are not to big making it tough on the needle. There are also other EQ's put in place to compensate for the materials natural sound.
With digital, FM and other "mass" media medium, compression is use so that the music can be played on a wide range of sources. It's troublesome for those who want more dynamics, more of the extremes.
Some where along the way though, digital compression and system compression have intermingled when they are two separate issues. Any type of recording compression happens within the domain of the frequency values, but this has very little to do with recorded space. The overall space of a recording remains the same in the signal pathway, even if compression is use on the values on the frequencies. Example, that 30'x30'x12' stage doesn't change in size, it changes content within that size.
fat compression and chop compression
With limiting (to make it easy) there are two main types. One is to chop the extremes, and the other is to raise the floor to fatten the middle. There's more to this but if you can picture these two that's good enough.
fat compression
Picture the signal being a 1" hose. The hose itself isn't going to get bigger or smaller but the content within that hose is being compressed, like turning up or lessening the amount of water going through it.
chop compression
Chop compression is like going from a 1" hose to a 7/8" hose. The extremes are cut giving more of an concentrated sound, but not as relaxed as the 1" would be giving.
All mediums do chop compression so you don't blow the drivers, and in high end audio part of this type of compression is built into products. (look at build vs sound)
soundstage space
Space of stage is the measuring tool for compression. The bigger you make your stage the easier it is to see the different types of engineering that goes on inside of that recording. The closer you get that stage to "real space" and "real size" the easier it is to see the tonal balancing, the pickup patterns, the physical parts of the recording and all the fun attributes audiophiles love to listen for. Space is what host those attributes and they change as the soundstage is bigger or smaller.
system compression
It's important to get a grip on system compression cause this is what you are going to make your judgements by. Go back to the talk on size. 30'x30'x12' squeezed (compressed) down to 12'x4'x7', reshapes all the musical characters. All of the many things you want to name from transparency, dynamics, tonal balance, body, whatever audiophile buzz word are conditioned upon the size of the signal host, the stage.
in listening
In listening you may hear frequency clustering (a common problem). The mid to mid highs on a recording may sound bright or hard. If you hear this look at the size of your stage and you will find that the stage has colapsed in some part. The recorded signal may be there but a part of the system is causing that signal to be compressed and as a result hard squeezed highs.
Lets look at system compression
I'll get into this more in a bit but want to show you something. Play a recording on tape vs table vs Cd. Notice the change in size on your playback when comparing the same recording on these three mediums on the same system? The smallest stage more times than not will be playing the highs most congested. As the stage goes up in size with the other mediums the highs smooth out. Do this as you compare and notice not only the sonic changes but also how they relate to the actual size of the stage presented. If your system is revealing all 3 mediums will out do each other depending on the recording. Some will sound better on the tape, some the vinyl and some the CD. Look at http://tuneland.techno-zone.net/t268-the-audio-code where I will cover this more, but will lay down the foundations here (until the flamers come lol).
michael green
MGA/RoomTune
http://tuneland.techno-zone.net/
Since I have been here I have noticed that the word "compression" comes up a lot. It's like compression has been linked to distortion, so it's probably a good idea to start talking about this because compression comes in a few forms as well as distortion.
You could take the approach that because compression is changing the audio signal from it's original state, this makes compression a form of distortion. However if you go this far, you would also have to say that microphone pickup patterns are also a form of distortion.
I prefer to look at distortion from a more practical view point. My view of distortion is any time the oscillating patterns in energy go out of tune. This makes it a little easier for us in this hobby because we know what happens when instruments go out of tune, but this same thing happens with equipment, rooms, speakers, along with anything in the audio pathway.
the sound of distortion
It's important to know the sound of distortion, or should I say sounds. In this hobby a lot of guys pull out the distortion flag without knowing the cause or what it even sounds like. For example they will claim that a recording is distorting when it is actually their play back system. Along with this we need to take a look at system compression vs recording compression. If you have a system playing a recording that is 30'x30'x12' in size and the system is playing it back at 12'x4'x7' this is system compression not recording compression. Recording compression (limiting) brings the middle dynamics up to meet the extremes, and many times cuts the tops of the extremes so that the music is easier to play. On a piece of vinyl you want the lows chopped so the grooves are not to big making it tough on the needle. There are also other EQ's put in place to compensate for the materials natural sound.
With digital, FM and other "mass" media medium, compression is use so that the music can be played on a wide range of sources. It's troublesome for those who want more dynamics, more of the extremes.
Some where along the way though, digital compression and system compression have intermingled when they are two separate issues. Any type of recording compression happens within the domain of the frequency values, but this has very little to do with recorded space. The overall space of a recording remains the same in the signal pathway, even if compression is use on the values on the frequencies. Example, that 30'x30'x12' stage doesn't change in size, it changes content within that size.
fat compression and chop compression
With limiting (to make it easy) there are two main types. One is to chop the extremes, and the other is to raise the floor to fatten the middle. There's more to this but if you can picture these two that's good enough.
fat compression
Picture the signal being a 1" hose. The hose itself isn't going to get bigger or smaller but the content within that hose is being compressed, like turning up or lessening the amount of water going through it.
chop compression
Chop compression is like going from a 1" hose to a 7/8" hose. The extremes are cut giving more of an concentrated sound, but not as relaxed as the 1" would be giving.
All mediums do chop compression so you don't blow the drivers, and in high end audio part of this type of compression is built into products. (look at build vs sound)
soundstage space
Space of stage is the measuring tool for compression. The bigger you make your stage the easier it is to see the different types of engineering that goes on inside of that recording. The closer you get that stage to "real space" and "real size" the easier it is to see the tonal balancing, the pickup patterns, the physical parts of the recording and all the fun attributes audiophiles love to listen for. Space is what host those attributes and they change as the soundstage is bigger or smaller.
system compression
It's important to get a grip on system compression cause this is what you are going to make your judgements by. Go back to the talk on size. 30'x30'x12' squeezed (compressed) down to 12'x4'x7', reshapes all the musical characters. All of the many things you want to name from transparency, dynamics, tonal balance, body, whatever audiophile buzz word are conditioned upon the size of the signal host, the stage.
in listening
In listening you may hear frequency clustering (a common problem). The mid to mid highs on a recording may sound bright or hard. If you hear this look at the size of your stage and you will find that the stage has colapsed in some part. The recorded signal may be there but a part of the system is causing that signal to be compressed and as a result hard squeezed highs.
Lets look at system compression
I'll get into this more in a bit but want to show you something. Play a recording on tape vs table vs Cd. Notice the change in size on your playback when comparing the same recording on these three mediums on the same system? The smallest stage more times than not will be playing the highs most congested. As the stage goes up in size with the other mediums the highs smooth out. Do this as you compare and notice not only the sonic changes but also how they relate to the actual size of the stage presented. If your system is revealing all 3 mediums will out do each other depending on the recording. Some will sound better on the tape, some the vinyl and some the CD. Look at http://tuneland.techno-zone.net/t268-the-audio-code where I will cover this more, but will lay down the foundations here (until the flamers come lol).
michael green
MGA/RoomTune
http://tuneland.techno-zone.net/