Wiggum Posted December 31, 2001 Share Posted December 31, 2001 Hey all, I've become obsessed with compression lately (trying to learn as much as I can), but I can't quite grasp the concept of expansion. If compression reduces dynamics in a recording, does expansion (the opposite) increase the dynamics of a recording (?) I guess the more important question is: [b]Under what circumstances would you use expansion?[/b] Can you give me an example? If compression "brings up" the softer sounds in a recording, does expansion push them down into inaudibility? I thought I read that you can use it for shortening decay times, but I could be wrong. Any thoughts? Wiggum [ 12-30-2001: Message edited by: Wiggum ] Link to comment Share on other sites More sharing options...
fantasticsound Posted December 31, 2001 Share Posted December 31, 2001 Let me answer part of your question. Expansion IS used to increase dynamics. In analog wireless, both VHF and UHF, compression is used to create a low dynamic signal for most powerful, reliable transmission, then, upon reception, the expansion circuit attempts to recreate the dynamic range of the input signal. I've yet to see an analog wireless that does this well, so analog wireless always ends up sounding slightly compressed. That's the beauty of digital wireless. Compressing the data signal doesn't alter the audio data. Dolby noise reduction for tape machines used the same principle to encode signal on magnetic tape. by compressing the input, the signal was "placed" further from the tape hiss (the noise floor). Upon playback, the expansion affected [i][b]both[/i][/b] signal and noise, reducing the tape hiss. Dolby products used multi-band compression/expansion, targeting the areas where tape noise is most noticable. Many frequencies were left alone. I'm not sure how expansion is used, if at all, by itself. Anyone else? It's easiest to find me on Facebook. Neil Bergman Soundclick fntstcsnd Link to comment Share on other sites More sharing options...
Danny M Posted December 31, 2001 Share Posted December 31, 2001 [quote]Originally posted by Wiggum: Hey all, If compression reduces dynamics in a recording, does expansion (the opposite) increase the dynamics of a recording (?)[/quote] Technically speaking, yes. An example might be a recording with a noise floor at -30 dBFS (not so good, but it's just an example), and a signal that goes all the way up to 0. If you set the threshold of the expander to -29 dBFS and and set the rest of the box up so that you get 10 dB of attenuation, then you would effectively increase the dynamic range of the recording from 30 dB to 39 dB. (Of course, when the expander isn't performing any attenuation the noise floor is still there. Obviously, the expander isn't capable of putting in signal information that isn't there to begin with.) Also, gating and expansion are the same thing, with the exception of gating being a much more severe attenuation than expansion. [quote]I guess the more important question is: [b]Under what circumstances would you use expansion?[/b][/quote] Some folks have problems with things like having their tom tracks receive a lot of leakage from cymbals. (Some people also consider it anathema to expand/ gate toms, but nevertheless.) You could also use expanders/ gates in live sound situations to help keep control over a number of mics that have to be open at once. Expanders/ gates are also nice to put before compressors, to keep the noise floor from getting pushed up too severely. Just as in compression, the use and abuse of expansion/ gating is limited only by your imagination. [quote]I thought I read that you can use it for shortening decay times, but I could be wrong.[/quote] Given the right setup, expansion/ gating can certainly be used to shorten decay times. (How much trouble it takes to get the effect you want is, of course, effected greatly by the envelope of the sound.) -Danny Grace, Peace, V, and Hz, Danny Link to comment Share on other sites More sharing options...
Magical Pig Posted December 31, 2001 Share Posted December 31, 2001 Expansion is when you have a bowl full of stink bud or hash and you think you took a normal hit, but when you try and hold it in you start coughing like a muthafucka...THATS what expansion is. Glad to help... ;) Scott Benson www.syborgstudios.com Link to comment Share on other sites More sharing options...
Hippie Posted December 31, 2001 Share Posted December 31, 2001 [quote]Originally posted by Magical Pig: [b]Expansion is when you have a bowl full of stink bud or hash and you think you took a normal hit, but when you try and hold it in you start coughing like a muthafucka...THATS what expansion is. Glad to help... ;) [/b][/quote] Funny, I thought that was a local Michigan thang...ya know, the phone call that goes somethin' like, "Hey dude, I got some expando you may be interested in" :D In two days, it won't matter. Link to comment Share on other sites More sharing options...
Wiggum Posted December 31, 2001 Author Share Posted December 31, 2001 Interesting... So it is used as a corrective measure, rather than to get a certain sound. Chaining an expander before a compressor is an interesting concept. You are then reducing the noise floor before the compression, thereby amplifying the signals you are trying to reach, and not the noise. This all came about when I was reading the manual for my Waves C1. The manual is a phone book, and Waves provides numerous details for setting up compression, expansion, etc, but they assume that you know exactly what all this stuff does. Some of the presets are combination compression and expansion, so I assume this is mimicking the set-up Danny mentioned (lowering the noise floor and compressing the result). Thanks for the help guys, Wiggum Link to comment Share on other sites More sharing options...
Uh Clem Posted December 31, 2001 Share Posted December 31, 2001 [quote]Originally posted by Magical Pig: [b]Expansion is when you have a bowl full of stink bud or hash and you think you took a normal hit, but when you try and hold it in you start coughing like a muthafucka...THATS what expansion is. Glad to help... ;) [/b][/quote] LMAO :D If you don't cough, you don't get off. Steve Powell - Bull Moon Digital www.bullmoondigital.com Link to comment Share on other sites More sharing options...
Danny M Posted December 31, 2001 Share Posted December 31, 2001 [quote]Originally posted by Wiggum: Interesting... So it is used as a corrective measure, rather than to get a certain sound.[/quote] Well... Actually, it's whatever you can make the box do. For instance, you can gate a snare reverb (that only has the snare in it) to get a sound that several people on this forum have an almost irrational hatred for. You can also do fun things like running a continuous signal (like a 50 Hz tone) through a gate, and then have the gate keyed by a split from a kick drum. Blend the kick and the gated tone to taste for the classic rap boom. An instructor of mine at the Conservatory once asked the class if anyone played bass guitar besides him. One guy raised his hand. The instructor pointed at the poor student and said, "You play too much s!@#." He then proceeded to gate the bass guitar, keyed by the kick drum. It definitely kept the kick and the bass in lock step. (It should be noted that this instructor is a highly professional guy with an appreciation for good musicianship. He plays bass himself. I'm sure he wouldn't do this without permission [b]and[/b] good reason.) -Danny Grace, Peace, V, and Hz, Danny Link to comment Share on other sites More sharing options...
MixterRader Posted December 31, 2001 Share Posted December 31, 2001 Think of an expander as a gate that doesn't close all the way Be a professional musician. Or just sound like one! Produce music with THOUSANDS of loops and effects. Link to comment Share on other sites More sharing options...
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