Well thanks everyone for your contributions to this debate, it has certainly moved on my thinking with regard to the best volume levelling process. Perhaps inevitably though it has raised as many questions as it has answered, and so I thought that I would post this message, a summary of my understanding of the different software and the pros and cons. May someone wants to let me know if I’ve got the basics right, or answer some of the questions raised………
Sound quality issues/processing of original file:
In both programs (L2 or Wave Hammer plug-ins and replay gain) the original file is unaffected, but obviously it is processed by these programs when burning to cd. The best description I have found of what L2 (or Wave Hammer, I will use L2 only from now on, but could of course be referring to both plug-ins) is actually doing is from the user guide:
“the maximum level of a digital signal is governed by the highest peak in the file. simple normalisation finds the highest peak, then raises the entire signal so that this peak is at the maximum value. However, many of these peaks may be of a very short duration and can usually be reduced in level by several dbs with minimal audible side effects”
so L2 is actually making changes not only to the overall signal level, but also to the range of the signal, limiting its highest levels, so that the db level of the overall signal can be increased. To put things simply then it is effectively changing the character of the signal as well as its amplitude. Now of course the aim is to do this without changing the perceived sound or quality of the original source. The danger is that music processed through L2 will sound ‘flat’ because the range of the signal has been limited or reduced. I presume that the skill here is to apply settings that boost the signal without changing the sound. Personally I have not found my processed tracks to sound flat, but I have heard this complaint levelled against Wave Hammer on forums.
Now in replay gain, because there is no function to limit the very high levels, it needs to find a lower overall gain level in order to avoid clipping. The disadvantages of this process are relatively higher noise levels as the signal is (nearly always) being pushed down relative to the noise level. Is there also a second disadvantage here, because I will not be getting the best out of my amplifier by putting in a lower signal (i.e. the quality of the output of amps is better at lower settings on the volume dial), or am I talking about the same process here? The advantages of replay gain is that it only alters the amplitude of the signal, and not the character.
Time issues:
Obviously given that I need to make individual settings for each track in L2, Replay Gain is much more time friendly. Furthermore, because all of my music is compressed as .ape files, I need to convert to .wav format before applying L2, which is more time.
Storage space:
Because L2 does not change the actual file, I cannot re-compress to .ape and keep the L2 information (is this right?). So this has implications for storage capacity – all of the tracks that I want to use for burning compilations will need to be stored as .wav files, so that they can be burned accurately using CD Architect. I am aware that there is a lossless compressed format for Sonic Foundry software (.pca), but this is not supported in MC9, which I want to use as my media player.
Fine adjustments to sound levels:
From my experience of using both replay gain and the plug-ins, it is rare that these processes leave all of the tracks in a given playlist exactly the right volume levels. Maybe one or two of the tracks still sound louder. At present I am not sure how to make fine adjustments to tracks after processing (and even if it is possible to do this). Obviously I cannot reduce gain level in L2, so is there another plug-in/process for making small adjustments (to either increase or decrease the signal)?
DJing on my laptop:
OK, here is another potential spanner in the works. Up until now I have been using CD mixers to DJ. With this in mind I am tempted to use L2 just for my DJ tracks where a high signal level/punch is important, and replay gain for stuff I’ll listen to at home (because of the time saving factor). However, now I have some rather tasty DJ software, and I am going to experiment using my laptop for DJing. Now, if I want to have my DJ tracks at a high and relatively equal volume level, both L2 and replay gain will not help me as the information from these processes will not travel with the file to DJ software programs. What I need is a process similar to L2 that will permanently change the original file. Can L2 or replay gain do this? I am aware that MP3 gain does this, not sure about Wave Gain. What do you suggest? I don’t mind changing the files for DJ tracks permanently because I can make copies of files first. Of course I can change gain levels within DJ software, but it does make life easy to have tracks about the same level from the start.
Well, I think that’s about it, a bit of a missive I know………
Nick.