Expander question

[Danny Wyatt]

I've never used any expander plugin, but my thoughts were always that an expander is just a compressor with an auto-gain. Is it more than that? Wouldn't we be able to achieve the same results by using a compressor and since Logic comes with several types of compressors, we would be better off with the compressor only?

Edited July 27, 2022 by Danny Wyatt

[des99]

An expander pushes the signal below the threshold down. It *increases* the dynamic range of a signal.

A compressor pushes the signal *above* the threshold down. It *decreases* the dynamic range of a signal.

They are not the same process.

[Danny Wyatt]

1 hour ago, des99 said:

An expander pushes the signal below the threshold down. It *increases* the dynamic range of a signal.

A compressor pushes the signal *above* the threshold down. It *decreases* the dynamic range of a signal.

They are not the same process.

Oh ok. I tried on a drum loop and I indeed experienced that increase in dynamic range, but thought I was maybe experiencing something weird. It makes sense.

I was maybe thinking about downward compression vs upward compression then...? Would those be what I was referring to?

[des99]

24 minutes ago, Danny Wyatt said:

I was maybe thinking about downward compression vs upward compression then...?

"What is upward compression? Upward compression is a type of dynamic range compression that boosts the amplitude of an audio signal below a certain threshold while maintaining the amplitude above the threshold. Upward compression is available in digital plugins and via parallel compression with hardware or software."

So upward compression is compressing the signal below the threshold and turning it up (rather than compressing the signal above the threshold and turning it down).

Compression always reduces the dynamic range, expansion always increases it.

Edited July 27, 2022 by des99

[Danny Wyatt]

54 minutes ago, des99 said:

"What is upward compression? Upward compression is a type of dynamic range compression that boosts the amplitude of an audio signal below a certain threshold while maintaining the amplitude above the threshold. Upward compression is available in digital plugins and via parallel compression with hardware or software."

So upward compression is compressing the signal below the threshold and turning it up (rather than compressing the signal above the threshold and turning it down).

Compression always reduces the dynamic range, expansion always increases it.

I see. I guess it's the first time I understand what that actually does.

So basically in upward compression, the audio above the threshold is ignored and the threshold now acts like a "ceiling" for the audio below it, so it compresses all the audio below (like a normal compress would) and then turns it up towards the threshold. Right?

So a practical use for that would be to compress the "meat" of the sound, while preserving the transients, for example.

How to achieve upward compression in Logic?

Edited July 27, 2022 by Danny Wyatt

[des99]

Upward compression as a single process is not that common. ADPTR Sculpt has an upward compressor, as well as a regular compressor.

What most people do to achieve this effect is use parallel compression - compress heavily (which brings up the low level stuff but also compresses the transient peaks), and then mix in the dry signal, which brings the transient peaks back in.

Edited July 27, 2022 by des99

[Danny Wyatt]

59 minutes ago, des99 said:

ADPTR Sculpt has an upward compressor

I was asking more about stock plugins...?

I was thinking about parallel compression as well, but if we think about it, it's not exactly the same, even though it's similar. When you add the parallel/super compressed version, you are also increasing the amplitude of the transients on the original source, whereas with upward compression it seems that the transients (when above the threshold, of course) will remain intact in terms of amplitude and only the audio below that threshold will be compressed and pushed up. Does it make sense?

[des99]

56 minutes ago, Danny Wyatt said:

I was asking more about stock plugins...?

I know. And the fact that I could directly recall *one* compressor plugin that has a proper upward compressor (and there's probably a few more I can't recall right now), but yet I know of probably hundreds of regular compressor plugins, should go someway to indicate my claim that "pure" upward compression is not that widely used.

If Logic had one, I would surely have noted that

56 minutes ago, Danny Wyatt said:

if we think about it, it's not exactly the same, even though it's similar.

I'm well aware 😉 and if you read my words, I deliberately didn't claim it was exactly the same (I did expect you to raise the point though  ). If you google it, parallel compression is regarded as "a form of upward compression", and that it is.

And it's a very widely/commonly used method, supported by many plugins (including Logic's own), and is sufficiently similar that it's a perfectly acceptable tool to use to achieve this effect (which is all about bringing up low-level detail and density), and consequently not many people seem to bemoan the lack of upward compressors.

In practice, while it's not exactly the same, it's close enough that it doesn't really make that much difference, at least in my opinion.

But go ahead and play with a compressor that has a proper upward compressor (and one that doesn't just implement a regular parallel compressor for this internally, I wouldn't be surprised if some naive implementations do) and see what you think. I think Sculpt is a pretty unique tool on things like drum loops and can bring up low level detail really nicely (you can pick it up for $6 if you're quick), but I'm sure I could do a lot of those things with regular parallel compression if necessary - it's just more convenient in the plugin as the workflow is simpler.

Again, upward compression is an approach and, like many audio processes can be implemented in many different ways, so isn't going to sound the same between plugins, just like different compressor plugins don't sound the same.

Edited July 27, 2022 by des99