negative compression ratios

losthighway · Post by **losthighway** » Sat Oct 25, 2008 11:16 am

Do you ever use this?

Has it any handy applications in the recording studio, or is it just something designed by crotchety FOH sound guys to punish bands for turning their amps up mid set?

0-it-hz · Post by **0-it-hz** » Sat Oct 25, 2008 6:58 pm

uh... negative ratios = expansion I think... not good for anything in Live sound except blowing up everything.

I use light expansion to bring "pop" to dead or poorly recorded demos/4-track/???

It's a dangerous tool, 1:1.3 is a BIG change so be careful.

losthighway · Post by **losthighway** » Sat Oct 25, 2008 7:30 pm

I was talking about-
-1:1 like on a dbx unit.

But I do have some plugins w/ those expansion type ratios. I'll keep that in mind.

thunderboy · Post by **thunderboy** » Sat Oct 25, 2008 7:31 pm

0-it-hz wrote:uh... negative ratios = expansion I think... not good for anything in Live sound except blowing up everything.

Oh, come on.

Compression:Limiting::Expansion:Gating

Expansion can be very useful, and more musical than gating IMO.

Any dynamic process can be dangerous if you don't know what you are doing. Brick-wall limiting used improperly will fry your drivers very nicely.

jt

rwc · Post by **rwc** » Sat Oct 25, 2008 8:40 pm

losthighway wrote:designed by crotchety FOH sound guys to punish bands for turning their amps up mid set?

OMFG

i never thought of using it this way before

you could have the mic on the guitar amp going to an expander's sidechain via aux send. the expander is on a richard simmons exercise tape loop. the richard simmons is fed directly to guitarist's monitor.

I hate to be all would love teaching but hates students, but that scenario made me laugh!

@?,*???&? · Post by **@?,*???&?** » Sun Oct 26, 2008 8:34 am

Maybe it's just me, but I've found that negative ratio on the Renaissance compressor plugin sounds great.

FlowersForHuman · Post by **FlowersForHuman** » Sun Oct 26, 2008 11:56 pm

I'm not following so maybe someone could help me out. If it isn't "expansion" then I'm not sure what -1:1 would mean in the physical realm...what is actually happening during "negative" compression?

rwc · Post by **rwc** » Mon Oct 27, 2008 1:21 am

the only thing i can think of is back in time.

in compression, as you raise the ratio, what it is doing is acting on the waveform afterwards.

like so

turning

/
/
/

into

-`"
/

that's an absolutely terrible fucking picture. look at it in a plugin. you see the line come down as you increase the ratio, clockwise.

maybe it comes down the other way, counter clockwise.. as in, audio going above the threshold at 0:35:500 will compress audio at 0:35:200

backwards compression.

obviously, impossible in analog. but perhaps achievable with a plugin.

I really wonder what that would sound like now.

0-it-hz · Post by **0-it-hz** » Mon Oct 27, 2008 6:59 am

I insist that we not define what this thing is... but keep the opinions comin!

losthighway · Post by **losthighway** » Mon Oct 27, 2008 11:38 am

Ok....

On a Dbx 160 unit you have standard comp ratios up to inf:1. A full on brickwall limiter. After that you get -1:1 which means that signal over a certain level actually gets reduced more. So louder after that threshold coming in, means quiet coming out. The manual actually references its application in live sound.

No one has seen this?

I don't mean to be on a high horse, obviously I have no clue what it would be good for. I just noticed it on the unit and had to say hmm......

GooberNumber9 · Post by **GooberNumber9** » Mon Oct 27, 2008 11:56 am

losthighway wrote:On a Dbx 160 unit you have standard comp ratios up to inf:1. A full on brickwall limiter. After that you get -1:1 which means that signal over a certain level actually gets reduced more. So louder after that threshold coming in, means quiet coming out. The manual actually references its application in live sound.

This is negative compression, which is different from expansion. If I could post a graph it would explain so much better.

2:1 Expansion: 2 dB increase of input leads to 4 dB increase in output
2:1 Compression: 2 dB increase of input leads to 1 dB increase in output.
-1:1 Compression: 2 dB incease of input leads to 2 db decrease in output.

What is it good for? Umm....
Ok, suppose you want to hear the snare drum really well when the drummer is playing quietly, but when the drummer plays loud, it bleeds into all the vocal mics and you need to basically turn off the snare. Negative compression on the snare mic will turn that mic down as the drummer gets louder.

the finger genius · Post by **the finger genius** » Mon Oct 27, 2008 12:48 pm

GooberNumber9 wrote: -1:1 Compression: 2 dB incease of input leads to 2 db decrease in output.

What is it good for? Umm....
Ok, suppose you want to hear the snare drum really well when the drummer is playing quietly, but when the drummer plays loud, it bleeds into all the vocal mics and you need to basically turn off the snare. Negative compression on the snare mic will turn that mic down as the drummer gets louder.

Really? But wouldn't you just limit the snare in this situation? Would you really want to reverse the drummer's intended dynamics? Maybe I'm just nitpicking, it could probably be a cool effect....

joel hamilton · Post by **joel hamilton** » Mon Oct 27, 2008 2:03 pm

I use negative compression ratios in parallel situations frequently.
Like if the direct snare sound (close top mic, lets say) is what you really want to hear when the drum is struck, but then you want to hear the aftershock from the ambient room mics... you can get the room mics to essentially "shut off" during the snare hit by using the snare top multed to the key in of a compressor on a buss. so you have the whole kit getting ducked by the snare mic. i will put an aux into the sidechain, so i can get a kit balance working in the parallel return that works well with he tempo/song/etc/etc by putting MORE kick into the SC to make it duck a little more of the cymbals, or maybe less so it doesnt pump on the kick but des duck for the snare and toms so they appear a bit closer.
Reverse ratios are totally great for mutant situations.. think of it more like "intentional overshoot" so when a snare drum is hit 1 db louder, you can get it to drop 2 db in level. WHenever we talk about compression it sounds like it would make things worse, but if you semantically reverse your thinking and say "I can turn up the snare volume 2-3 db overall average without getting any nasty spikes in that one place when the drummer really hits the heck out of it" then it sounds like a better idea. A lower ratio makes for a more natural sounding snare drum in this case, but with a time constant applied to the sound. So you can do some envelope shaping of the snare and have it hold still for you to place it in the mix. It is rare that i will use a neg ratio for anything other than old school portishead swampy/mushy ducking type of drums, but when it is the thing, the couple of feed forward comps I have that are capable become very valuable to me...
Couple an inverse ratio with a good limiter and you can get some surreal sounds happening along side of some very big sounds... like those times where unfettered is not as real as messed with a lot, which can happen a bunch...

losthighway · Post by **losthighway** » Mon Oct 27, 2008 3:05 pm

Wow. Thanks Joel. That answer was so good I might save it and come back to it again later. That is a very sophisticated method, but the way you explained it I can see the application.

Schooled.....

the finger genius · Post by **the finger genius** » Mon Oct 27, 2008 3:10 pm

+1 to thanking Joel for the response. Makes sense now.

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