Please give me a quick tutorial on "Compressor/Expander/Limiter/Gate/Peak Limiter". (1 Viewer)

[Tuan Le]

Hi guys,

I would like to read up more on the use of "Compressor/Expander/Limiter/Gate/Peak Limiter". Can some one please give me a quick run down tutorial on these devices for home audio applications (karaoke, recording music and such....) Any links to PDF whitepaper would be greatly appreciated.

Thanks
-Tuan

 

[Philip Hamm]

Sorry, I don't think you'll get much help here. These devices are ususally used for compression in recording in studios. For stereos and home theater in general you don't want to use devices like this. (For Karaoke they will work great) In most receivers there is a digital implementation of compression in the name of "midnight mode" or "Dynamic range compression" to tame the sometmies extreme dynamics of soundtracks.

I have a dbx unit that I'm thinking of using in my new house in the tape monitor loop fo a stereo used for "through the house" in-wall speakers.

 

[ChrisWiggles]

There aren't used in home applications really, except for the aforementioned DD night mode compression.

Compression is, IMO, the enemy of good audio.

 

[Wayne A. Pflughaupt]

Here’s what each does:

Compressor – Boosts low-level signals, and “squashes” high-level signals. The result is a consistent level of audio output regardless of the intensity (of lack thereof) of the input. Very useful in broadcast - for instance, the DJ can whisper or scream into the mic and you, the listener, don’t have to constantly grab the volume control; the level you hear remains constant. Also useful in live audio for the same reason, especially for vocals as well as other highly dynamic instruments like drums.

For the end user (that’s us) I agree with Chris that compressors are the “enemy of good audio.” Compressors are the reason that music on FM radio sounds flat and lifeless compared to the same music on a CD. Compressors are over-used in recording studios, IMO, and the result is the same – the end product does not sound nearly as realistic and dynamic as it could. The effect is especially prevalent on vocals and acoustic instruments - piano, drums and cymbals, etc.

Expander – A.k.a. dynamic range expander, pushes down residual noise floor in the absence of a signal. For instance, audible background noise between songs on cassette tapes can be virtually eliminated.

Limiter – Similar to a compressor, but evens out only high-level signals while imposing no effect on low-level signals. Typically used to prevent signal levels from exceeding a pre-set limit, to keep a sound system or the inputs of a device from clipping.

Gate – Effectively shuts off a signal when it falls below a pre-set threshold. Typically used on mics when the presence of a signal is absent. For instance, a speaker using a lapel mic: the mic is very sensitive and will pick up ambient room noise when the speaker pauses between phrases. The gate can be set for a low threshold to shut off when he is not speaking. Set the threshold too high and it will cut him off when he speaks softly. Another common use is for micing drums. In this case the threshold is set high, to pass the signal only when the drum is struck, but immediately close so as not to “bleed” - pick up the other drums as they are struck.

Peak Limiter – See “Limiter” above.

As you can see, only an expander would be useful in normal home audio. For amateur singers in karaoke, a compressor or limiter would be a big “plus” especially if they are going to be recorded. There is really no use for a gate outside professional applications.

Hope this helps.

Regards,
Wayne A. Pflughaupt

 

[Tuan Le]

Wayne: As always, your posts are very helpful and informative. You rock!!!

Philip & Chris: I really appreciated the feedback from both of you.

-Tuan




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