I've normalized my entire CD collection using AudioCatalyst and used the highest VBR setting. Is there any benefit to running this volume adjusting kernal for me?

Your question seems to come from two places:

1) Misunderstanding of the difference between "Normalization" and "Dynamic Compression".

2) Misunderstanding of the dual-usage of the word "Compression".

Let's take the second one first:

The word "Compression" is used to describe two different things: The data compression process by which a WAV file is made smaller and turned into an MP3, and the completely unrelated dynamic compression that's used in the original audio production of the albums you listen to and the television shows you watch.

I assume you already understand what data compression means, let's move on to dynamic compression. From here on out, I'm going to refer strictly to dynamic compression.

What it it? It's like a "contrast" control for the sound. A compressor changes the relationships between the loud sounds and the quiet sounds. It can make the loud sounds quieter and the quiet sounds louder, giving the overall volume a smoother flow.

This differs from normalization in that normalization simply adjusts the entire volume of the track upwards until the loudest peak in the track hits 100 percent. Most of the CDs you buy are already normalized, so hitting the "normalize" button in AudioCatalyst rarely makes major changes.

Almost all of the recorded sound you hear, whether it be on TV, movies, or record albums, is already compressed to some degree. And usually multiple times. Let's take radio stations as an extreme example: When you listen to a song on the radio, the sound has already gone through several compressors at different stages. First, the individual instruments and voices were compressed to different degrees when they were recorded, each instrument with different settings. Then, during the mixdown and engineering of the album, some of the instruments were submixed and bounced down to combined tracks (such as the drums being combined into a single stereo track), and were probably run through another compressor in the process. The final mix was probably compressed a bit before it was sent to the mastering facility, and the mastering facility probably applied even more compression to the album. Then when the radio station plays the song, they heavily compress all of the music they play so that all of the songs appear to be at the same volume. This last one explains why songs sound different on the radio than they do when you buy the CD.

Another example is television commercials. They always seem to be louder than the TV shows because they are overcompressed. Both the TV shows and the commercials have the same volume peaks, it's just that the commercials are compressed so they hit that peak more often (almost constantly, in fact). This is completely deliberate on the part of the makers of the TV commercials. The only way around it (and some TV sets will do this for you) is to overcompress the TV shows themselves so that they're now as loud as the commercials.

A great discussion of compression and how it relates to the relative volume of CD songs is right here. Read it, it's terribly informative and it's written by someone whose job depends upon being very good with compressors.

Now, how does this relate to Rjlov's volume adjusting kernel?

Well, Richard's basically written a digital compressor with a very long attack time (although there are differences which I'll get into in a moment). It runs in real time on the songs playing in the Empeg. Its job is to increase the volume of the quiet parts so that they come out closer to the loud parts. The benefit of running this program is that it'll allow you to hear the quietest parts that were originally buried in the noise floor of the car.

It behaves slightly differently than a compressor, in that it doesn't use a fixed "slope" between the input voltage and the output voltage. Instead, it slowly increases the absolute volume towards a blind target until it clips, then instantly backs down if it detects a clip coming up.

This makes it sound a bit different from a straight compressor, but the end result is similar. I like it a little better. If you want to play with a real compressor, load up a wave file into Cool Edit and invoke their compressor filter. You'll be able to see how it works in their user interface and hear the differences.

One thing that Richard still needs to work on is its ability to handle mid-level volume passages. A passage with a medium volume isn't amplified as agressively as a very quiet passage. So the old problem of all your CDs sounding like they're at different volumes is mostly still there. Since I don't currently have the ability to alter the kernel's parameters, I don't have any way of experimenting to see if that's adjustable. If this software ever gets integrated with the Empeg's main user interface, then we'll be able to play with the settings and get different results. You have to be careful of this sort of thing, though, because an overcompressed album sounds bad.

Does this answer your question?

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Tony Fabris