Expansion versus Normalization

[paul]

[citguy]

[Derek]

[paul]

I would concur absolutely with this. It is not usually a good idea to keep reprocessing until the detected clicks drop to zero. This is because of the problem of 'false positives' The process of discriminating between clicks and music is never perfect and therefore, the more times you process, the more is the likelihood that you will pick up a lot of false positives. This may be what is causing the dull sound you are reporting.
As a matter of interest, if the reported number of clicks found is 0, does that mean that Wave Corrector has made no changes at all?

Regarding expansion before normalisation, I'm not aware of such a process. Expansion usually refers to the process of expanding a signal that has been compressed to fit into a transmission or recording medium, for example Dolby B. You wouldn't normally expand a signal unless it had previously been compressed.
Let me quote from a tutorial I found on the web:
"Vinyl recorded material suffers from a lack of dynamic range. The Cool Edit software allows you to define an "expansion" algorithm that can expand the dynamic range of the source material where you can actually create a wider dynamic range than the album had to begin with. This is another reason for the -6db initial record level. To expand the music's dynamic range, you need what is called head room to allow you the ability to increase the dynamic range without causing clipping. You will need to experiment with this to find the optimal settings. Generally expansion at 2:1 is over expanded and the default expansion offered is even more, 3:1. I generally run between 1.2:1 to 1.4:1 as a healthy value. You don't need to perform this step but it will add life to your music."
The author then goes on to specify a normalization step as well. Does this make the term "expansion" any clearer? if so, do you know what this step achieves different from normalization, and how?

[Derek]

[vinylmaster]

Hello all.

Regarding the expansion topic, before all this digital stuff came around, there were a few companies that produced hardware that performed a few of the tricks to which Paul originally referred, namely expansion.
dbx produced a few pieces of good equipment (believe it or not) that performed an expansion. For example, their "3bx" audio sound processor could expand a signal a bit.
From what I remember of the literature that came with the piece, dbx explained that vinyl had a certain compression in order to make the music physically fit on the record. Otherwise some of the crecendos we hear in classical music would literally ride off the record. The record companies "compress" the signals just a bit. The dbx processors could restore some of the dynamics. (Any errors in this explanation is solely mine.)

[citguy]

I have three Sanyo Super D noise reduction units whcih were Sanyo's answer to DBX back in the 70's. They are best used when recording on tape. The signal is "encoded" or compressed for recording then on play back it is expanded and the overall playback level is reduced thus lowering tape hiss to well over 90 dp signal to noise ratio. It is critical that the expansion and compression occur at the same "ratio" or all kinds of problems occur. When used properly it is impossible to hear "tape movement" at playback. I have never attempted to expand normal vinyl recordings. I am not sure it is possible. As I understand Wave Corrector's nomalization, the peak levels are determined and then the peaks are increased to maximum levels. But, I have wondered how the ratio of loudest to softest material is maintained. It has been my experience that when normalizing, the hiss level comes up also. So I have always applied the hiss and hum filter after normalization. I also have a Burwen Dynamic noise reduction unit which reduces noise on the fly mainly during quiet passages on fm, tape or vinyl. It also needs to be used with great care or additional unwanted effects can be introduced to the material.
Stan

[adaywayne]

[Glenn]

Hi everyone;

I recently joined this forum group and am intrigued by this ongoing debate regarding dynamics expansion. I've been recording LP to CD off and on for the past several years but kept putting it aside because I couldn't get the 'magic sound' I recall when I blasted these recordings in my youth. I've looked at software dynamic range expanders and other audio 'enhancers', but still couldn't get the rich, dynamic sound I knew was on these records.

In recent times, I've grappled with the definition of dynamics in terms of what we hear, or what impresses us as 'dynamic'. The question as to whether an LP is as 'dynamic' as a CD is becoming moot as the music on many CDs these days is recorded with far less actual dynamic range than what could be heard on LPs. Apart from the added RIAA equalization of LP's, both media apply normalization (as opposed to dynamics) to get the most sound out of them. My view now is not whether dynamic range is important; its more the normalization engineered into the recording itself that concerns me.

The question is what kind of normalization? Simple gain normalization is the same as turning the volume up to a set level. RMS normalization, on the other hand, essentially raises the average sound level of a recording within a given dynamic envelope. This tends to bring up the quieter passages more than the louder ones and is basically a form of compression, but the implementation of it is different. In this form, most of the instruments are lifted to a perceptually higher averagevolume, increasing their audibilty and the overall apparent clarity of the sound. If not overdone, it can make a recording sound more 'dynamic' by virtue of this effect. This is not news; practically every recording you've heard has had some form of what is effectively RMS equalization applied in the studio. You can see this in the waveforms in any wave editor. In the early days, it was more necessary in order to make full use of noisy recording media.

The practice of recording with a wide dynamic range, such as what one might experience with a full orchestra in a quiet concert hall, was experimented with in the earlier days of digital audio. It has fallen out of favour, as such recordings are impractical for the everyday listening environment of most consumers. In my experience, increasing the dynamics of a recording won't improve the sound. Rather, careful initial recording to the hard-disk with a mind to preserving the dynamics in the vinyl, plus the use of subtle equalization and maybe some RMS normalization (if necessary) will.

My current approach is to input the soundcard from the pre-amp as loudly as possible (metered typically within -.5db). I also apply real-time software sub-sonic filtering during recording to stabilize the written waveform for the fullest dynamic range possible. As my record player sits on the desk above the pc, I've taken extreme steps to minimize the vibration from the cooling fans, and have achieved a noise reduction of better than -10db this way. Plus, I always record with the speaker volume off. After recording, I clean the sound with Wave Corrector, doing a single level 3 scan, then make a few adjustments to the larger corrections. If the surface noise is still unbearable, I'll do a fingerprint noise reduction, but only as a last resort. In most cases with pop music , all that is required further is maybe a little bass eq, to simulate the punch that high volume feedback from the loudspeakers gives, or a bit of treble. Sometimes with quieter music, an RMS normalization of about -8 or -9 db brings considerable life to the sound. The effect is not as good as a studio track remastering, but it comes close. If I use it, I apply the bass afterwards; it gets quite a boost this way. Ofcourse, the gain has to be adjusted downward prior to this.

It has been my experience that this approach gives the best overall sound reproduction. If the vinyl groove is not too bady worn, the sound quality compares favourably against the commercial counterparts (especially the early transcriptions). If the groove is badly worn, or if the recording was poor in the first place, I haven't yet found a way to fix this. I have to agree with Derek: I don't believe that dynamics expansion will improve the sound in any way.

Glenn

[paul]

[Glenn]

[paul]

[Glenn]

[adaywayne]

[adaywayne]