Audacity Forum

I think it would be a good idea to have a sticky topic on the forum (as suggested by Gale in this post http://forum.audacityteam.org/viewtopic ... 459#p86276 ) as this would allow others to add suggestions. I realise there is a risk of it becoming a "spam magnet", but I think it is worth giving it a trial run, especially as whomper appears to be keen to add some software suggestions. As previously suggested, if the topic becomes popular, then we can look at devising a work-flow for transfering suggestions to the appropriate lists on a routine basis.

I have started a sticky topic here: http://forum.audacityteam.org/viewtopic ... 913#p86913
If any of the moderators would like to add or change anything in the starter post, please feel free to edit it.

kozikowski wrote:<<<The Hard Limiter was exactly what I was looking for.>>>

Then you win. Hard Limiting is a special purpose effect -- like a fuzz guitar -- that can do serious damage to the sound. That's why it's not right at the top of our recommendations.

Koz

I can see how sample precision lowers when you decrease the Wet level. Can you be a little more specific on the "damage" done, exactly?

Hard limiting is basically the same effect as distortion that is caused by recording too loud, though it can be made less harsh than digital clipping by increasing the "residual" level. Hard limiting distorts the peaks by squashing the tops of the waveforms, thus creating significant amounts of odd harmonics. The effect is very much like a fuzz box, except that the distortion is limited to the high peaks, whereas a fuzz box will be set with a much lower threshold so as to create distortion on lower level sounds.

To get a clear idea of what hard limiting does, try setting it to an extreme setting of "-20, 1, 0"

I already know exactly what Hard Limiter does. When there are really high sharp peaks that prevent the rest of the music from reaching an appropriate level, they need to be lowered so the track can be amplified without the peaks clipping. Hard Limiter sounds like it's exactly the tool to do that. It sounds like it could even the peaks so that through the whole song they are able to touch the edges of each channel. So to me, it sounds like audible damage can only be done if you lower the Wet level drastically, which could be compared to amplifying to -50dB and then reamplifying. But on the other hand, Wet level needs to be lowered enough to anti-alias the peak clipping. But I don't think that's a problem at all if done in the right amount since all that can be done is a re-interpolation: you won't be able to measure a difference in precision or notice that there is any noise introduced.

X-Fi6 wrote:they need to be lowered so the track can be amplified without the peaks clipping

The way that the hard limiter works is that it clips the peaks, though it can be set to do so more gently than hacking off the peaks flat. The harmonic distortion is of an identical kind to clipping the peaks, but not as much.

The hard limiter splits the sound into three components - the upper peaks (the bits above the threshold), the negative peaks (same, but negative going), and the middle bit.

If you set the "residual level" to zero, then what you get is just the middle bit. This is identical to clipping the peaks.
Here is a close-up of a sine wave that has had the hard limiter applied with settings of -6, 1, 0
The "Residual" part, is the other two parts. We can isolate these two parts by setting the Wet level to zero and the residual level to 1
Adjusting the "Wet" level scales the amount of clipped audio (the middle section). When set to 0, it is scaled down to silence, when at 1 it is at the original volume (first image) and when at 0.5 it is scaled (amplified) to half volume.

Adjusting the "residual" level scales the "peak" component in the same way.

Usually you would want to keep the Wet level at 100% and then add in a proportion of the "residual" components to "soften" the clipping effect.
Setting the residual level to about 0.3 is usually a good compromise, and produces a result like this:
If you look at the spectrum (Analyze menu > Plot Spectrum), you will notice that soft clipping produces the same odd harmonics as hard clipping, but at a lower level.

There are other types of limiters that produce lower distortion levels, but this type is simple and quick to use, and when used to just clip occasional peaks it is quite adequate. The distortion can in some situations be quite effective, for example, if used on a slightly dull recording of a cymbal or snare drum, it not only limits the peaks, but the distortion can add a bit of extra brightness to the initial hit. Odd harmonics are often described as less musical sounding than even harmonics, but in the case of percussive instruments such as these it is less important as the sound is essentially inharmonic.

Steve, you just posted what I know exactly already.

You mentioned "The way that the hard limiter works is that it clips the peaks, though it can be set to do so more gently than hacking off the peaks flat.". This is exactly what I want, isn't it?

dB limit sets the cutoff threshold. Residue level sets what percent volume the cutoff area should be, where 0 means 0% and 1 means 100%. Wet level means feathering the cutoff area, where 1 means feather only as far as -1 and +1 (meaning, no feathering at all) and 0 means feather all the way to 0 (which makes the track have no volume).

Tell me something I don't know like the negative effects.

Edit: I just read your last paragraph and it's informative. I'll look into the spectrum myself.

Maybe I missed something, but why compress? And how do you mix to make it more studio?

In what manner was your original copy recorded? Equipment wise.

Why do you need to make it more studio? Is it too flat? Or poppy or lispee?

And is it stereo?

Do you just want it to have more punch?

The reason we all like Chris's Compressor so much is that it increases the low passages of the show and suppresses the loudest ones automatically without seeming to do anything.

It's directly comparable to the "invisible" volume compression that an FM radio station does. I don't have it around any more, but I used to have A/B comparison test between the "internet" version of "Car Talk" and the version on LA's KPCC Radio. Millions of people are happy listening on the radio and compared to that the internet version is almost unlistenable. They just posted the raw feed and every time Tom would laugh, the volume increase was enough to set off smoke alarms and scare the cat.

A quick trip through Chris and the volume variations are back to where they should be for a comfortable listening experience.

You could not get that with straight peak compression.

As as I said, if you found a tool that works for you, then you win. The peak lopper-offer is much more indicated if you have a noisy phonograph record you're trying to process. Great differences between the pops and the music. Chris is helpless there.

Koz

By the way, you're speaking the advertising words of CBS Laboratories, the designer of the Audimax and Volumax FM Radio compressors. They reigned broadcasting for years. The Audimax was the slow, sloppy overall volume setter and the Volumax (or Volume-Ax in local speak) would come up behind it and surgically whack off the offending peaks.

It was OK at best, but it was the state of the art for a while.

Koz