Compressing, Amplifying, and Equalizing Some Older Recording

Special Interest Groups Audio Processing
1

I love the band Styx but some of their recordings leave much to be desired. When I listen to “The Grand Illusion” CD on my iPod, the volume is lower and the low end is weak compared to other music. I have toyed around a little and determined that I can make it sound better with a few tweaks. There are only a few peaks that reach -3dB but that’s not quite enough to amplify and boost the bass. I believe I need to use a hard limiter very lightly so that I can equalize, amplify, and compress the tracks but in which order? Also, which tools are the best and how do I determine the best compression settings. I have the 1.2 and 1.3 beta versions of Audacity so I can use either. I’ve also used http://pdf23ds.net/software/dynamic-compressor/ for some podcast listening so I have it.

Chris

2

Use Audacity 1.3.12
Set the track format to 32 bit (click on the track name and select “set sample format” from the drop down menu, then “32 bit”)

Try running Chris’s compressor on it’s own, just to get an idea what difference it makes. Compression ratio settings between about 0.5 and 0.7 will usually work well and the other settings at default.

Not enough bass? Undo the compression effect.

It may be useful to amplify the track by a negative amount (say -12 dB) and turn up the volume on your speakers - this will provide a lot more headroom so that none of the effects cause clipping while you are working on the piece. Audacity 1.3.12 can actually handle audio above 0dB without clipping, but some effects will automatically clip at 0dB.

Use the Equalizer effect and push up the bass frequencies - lots of experimentation here - test it out on short sections. You can increase the “Preview” time by going to “Edit menu > Preferences > Playback”

When you have the Equalisation as you like it, use the Amplify effect with the default settings.

Now apply Chris’s compressor.

How’s it sounding?
If it is now sounding good, use the Amplify effect again and set the “New peak amplitude” to about -1 dB
Listen to the whole thing and if you like it, export the finished piece as a WAV/MP3 file

Do not delete your original version - tomorrow, when your ears have rested, you may decide that you have overdone it and want to redo the whole thing.

3

Styx, nice choice.

I know what you are talking about with the CD’s. For some reason many new re-released cd albums that were once on LP now on CD, don’t seem to have what it takes.

You don’t have to compress or amplify. It is a matter of Equalizing. But not just turning up the bass and down the highs. Actually leaving the highs where they are is best. Try this EQing.

Before I give you the table, let me say that you are going to have to listen to the CD original first. With whatever you are listening to it on, cd/computer/stereo/earphones, the Left channel has to be selected properly. The left channel would be the channel that has the most thump, thump to it. If you have bass and treble controls, turn the bass up, the treble down, loudness on, and listen for the channel that has the most thump to it. The other channel should be more fingered sounding, like a fingered bass guitar or something. Once you locate the “thump” channel, you now know which is the left channel. The other channel is the right channel. Placement of the channels is important.

EQ as follows:

Left channel
Frequency 30 Hz 60hz 125hz 250hz 500 1K 2K 4K 8K 16K
dB gain 24 20 16 8 12 8 4 0 0 0

Right Channel
Frequency 30 60 125 250 500 1K 2K 4K 8K 16K
dB gain 24 20 8 16 12 8 4 0 0 0

With whatever you are recording to, program, tape, or CD deck recorder, you should lower the gain on both channels before applying these EQs. So for a computer program, use a tool to lower the volume of the wave for both channels. I generally just lower it about to 1/3 of what it originally was. Then apply the EQ, and if it isn’t loud enough then you just up the wave volume until it peaks. But I don’t usually use the program to modify EQing. I use my EQ decks and feed it in and record it with a program.

You mentioned Styx. I find that the Doors CD’s are that way too. No bottom. Too bright. This should fix it. If this EQ is too powerful, then just half the values above and that will do nicely too. I would descibe the EQ settings above as a really good “Jukebox sound”. These settings also work wonders on mono tracks. There are also tricks to make mono stereo, but that is another thread.

Try it and tell me how you like it.

4

I took a totally different approach before your reply. I looked at the “plot spectrum” graphs and compared them to some recent recordings. There’s quite a difference in the low end but the rest of the spectrum looks pretty good. I’ll try your method too and see how it sounds. thanks for the suggestions and I welcome more.

Chris

5

Just a little word of caution for chris1379: unless you have some very large speakers, it is unlikely that the speakers are going to be able to handle 30Hz, and pushing too much very low bass through small or medium size “reflex” speakers can cause permanent damage such as distorting or burning out the voice coils or even causing the voice coils to become partially detached from the cones, so if you try the suggestions from LPMasterTHD%0.002, take care with the volume and if you hear any rattling or knocking type sounds from your speakers, turn the volume down.