I have been studying the LUFS EBU R128 loudness level requirements for all commercial music. 
I would like to know how that relates to the K20 metering system. 
If I was going for LUFS EBU R128 which states that our loudness should not be more than -24, does that mean it is -4db lower than K20?
 

The spec is -23 LUFS (dB) +- 1dB.  So yes, the average loudness would be around 3-4dB less than K20.  It seems low, considering it would allow for many dB of headroom, but with heavy broadcast compression, it maintains dynamics of compressed pop music, while still allowing dynamic, sensitive music and speech compete and retain a similar loudness without much preparation.
 
This is a scale for broadcast production managers only, a producer of music for CD need not worry about the scale, there is no standard or requirement.   I have been in broadcast production for 8 years, music came in at all levels, it was my job to make sure it went out all the same.  

Rimshot
I would like to know how that relates to the K20 metering system. 

 
If I remember the little research I did a while back, the K system is based on more or less instantaneous reading of level (the averaging is done by eye) whereas EBU R128 takes into account a larger segment of the audio for its calculation (the whole piece ?)

If the material is an even level for most of the time the LUFS reading is usually about 2 to 3 dB lower than the K level you may be working at.  For material that varies more widely over the  course of the piece then the LUFS reading will be lower still.
 
Working at K system levels goes a long way to getting a good LUFS reading. eg working at K-14 will put you right in the ballpark -16 LUFS level which is desirable for iTunes etc..(assuming even levels for most of the piece which is what is often more common)
 
K system rms levels are still way more useful than peak levels. They tell you much more.

Thanks guys for the replies. I am learning more and more about loudness these days. 
For broadcasters, when they have to be held at specific levels no mater how the source was mastered (really loud or not), they broadcast at one level that is controlled by their compressors. If a lound mix is above the standard threshold, it will most likely sound a lot worse beacuase the broadcast will be compressing it so much to get it down to standard. By comparison, the softer mix that has retained many transients but not be as altered and therefore might sound better. 
In these scenarios, the constant is that the user's playback volume becomes the active element. 
If listening to a station that adheres to this new standard, the over music, news, ads, etc, will all be broadcast at the same output level. Therefore you will not have to be turning up or down your volume as much.
 
THere is a new movement that is working on the volume issue control as well. 
It seems the bottom line is that music will have to adhere to these new loudness standards and everyone will want the best sounding tracks in the broadcast medium. As I have read, what that takes is the source to be compliant and the end user to simply turn up their volume controls to compensate. 
 

I agree with Daniel though in that for CD production there is still no standard (yet?)  If I mastered a CD at -23 or -20 or even -14 the client would still not be happy because it would not be loud enough.  I find this a bit upsetting still.  I still have to take things way up to -10 or even higher.  Attitudes are taking longer to flow onto clients and their CD's.
 
It is great in that the movie theatre world and broadcast there are some references and that to me is a good thing and a great start.  Let's hope in time things start to flow onto CD's.  It's up to us to a certain extent to try and explain the virtues of mastering a little softer, letting the music breathe a little more and lets those transients and dynamics come though.
 
I use three modes of metering in all.  K metering to start then LUFS and also the DR meter is good to run over things too.  I would love to see K-14 being a ref standard for CD.  It seems to offer a great compromise between loudness and dynamics and punch.

Hi Jeff, 
I was hoping you would comment on this (I pretty much thought you would).
I have learned a lot from you about the K system and it is all making a lot of sense to me now. It is hard to image the future without a standardization with output levels across the board. 
If the end user just needs to crank up their system a bit to adjust, it is not a rude trade off at all. 
Getting there will be hard becuase no wants their masterpiece to sound weeker than another's even though with a little volume, it could sound much better due to the better headroom and dynamic range. 
 
This is all good to get to know now. Happy New Year!
 
Update: Here is a good article on a new K System v2 standard which is trying to evolve the K System now that the EBU R128 is in force:
http://techblog.studio-compyfox.de/media/tech-doc/tech001_2012-Q2_K-System_v2.pdf
 
It is also interesting to read about the "new loudness alliance". 
 
 

Jeff Evans
I agree with Daniel though in that for CD production there is still no standard (yet?)  If I mastered a CD at -23 or -20 or even -14 the client would still not be happy because it would not be loud enough.  I find this a bit upsetting still.  I still have to take things way up to -10 or even higher.  Attitudes are taking longer to flow onto clients and their CD's.
 
It is great in that the movie theatre world and broadcast there are some references and that to me is a good thing and a great start.  Let's hope in time things start to flow onto CD's.  It's up to us to a certain extent to try and explain the virtues of mastering a little softer, letting the music breathe a little more and lets those transients and dynamics come though.
 
I use three modes of metering in all.  K metering to start then LUFS and also the DR meter is good to run over things too.  I would love to see K-14 being a ref standard for CD.  It seems to offer a great compromise between loudness and dynamics and punch.

I'm just wondering how your clients might respond if they heard their -10 or louder CD master A/B'd against the crushed dynamics version that iTunes or Soundcloud, e.g., would convert it to. Or do you create a main mix at a more suitable level, and then master the various distribution channel versions?

 
I'm more than happy to turn up the volume on a piece that has more dynamic range.  It's having to turn the volume back down on the next song that's a wall of noise that is annoying.
 
 

Well stated Paul. Volume control is all over the place. I guess in your own home you can control it. With broadcast levels being demanded, radio and TV should actually get better.