Post by: George_ on December 09, 2005, 02:40:19 am
Have some problems about understanding compressors:
Signal (80dB)=>Compressor[inputstage (example 80dB)=>treshold (-10dB)==> Ratio f.e. 4:1=>outputstage(20dB)==> makeupgain (by 10dB)==>outputstage(treshold+10dB)]==> Signal (80dB)
I dont know if this treshold+makeupgain is right.. please excuse
if I have a change by 29dB in the inputstage it will be only a 6/7dB change in the output.. I am cutting dynamics
so.. in principal I have a compression.. the signal is getting compressed.. smaller, less dynamic.. if I use the makeupgain I have the same signal as before?
dont get me wrong.. I hear a clear diffrence between compressed and not compressed.. but I wanna understand it in detail.
cheers George
add: I read through this and its becoming clearer http://www.epanorama.net/links/audiocircuits.html#compressor
Post by: j.hall on December 09, 2005, 10:34:34 am
so let's say you put a kick drum to a comp. you set ti all up to something you like, but the gain reduction meter is showing you -6 of compression on the kick drum. you love the tone you got, but now the kick drum is 6dB quieter coming back to the console.
you grab your "make-up gain" knob and simply make up the difference of that 6dB. the output make-up gain is to simply get you back to where yous started. you can use it however you like.....make it louder, quieter....whatever. but don't think of it as a "uncompression" knob.
Post by: Fig on December 09, 2005, 11:57:16 am
| noGearslut wrote on Fri, 09 December 2005 01:40 |
dont get me wrong.. I hear a clear diffrence between compressed and not compressed.. but I wanna understand it in detail. |
Mr Hall is right on.
However, I have always found it to be useful to explain that a compressor changes the dynamic RANGE of a signal.
The make-up gain just brings the top of the newly compressed RANGE back to where it was originally (or sometimes past that, or below that - depending, of course).
The ratio determines what a resulting output will be based on a given input. For example 2:1 compression (regardless of make-up gain setting) requires a 2dB input to give a 1 dB output. If the dynamic RANGE of the input is, say, 10 dB from its queitest sound to its loudest sound, a 2:1 ratio will compress that RANGE (sorry to keep emphasizing it, but it is the most important aspect, methinks) to merely 5 dB.
That being the case, the loudest sound may need to be turned up (via make-up gain) so that the overall output is the "same" as the uncompressed version of the same thing.
However, sometimes one will choose to compress and NOT adjust make-up gain, instead trying to "knock down" the peaks.
Does that help at all?
Warm analog regards,
Fig
Post by: j.hall on December 09, 2005, 12:24:20 pm
| Fig wrote on Fri, 09 December 2005 10:57 |
The ratio determines what a resulting output will be based on a given input. For example 2:1 compression (regardless of make-up gain setting) requires a 2dB input to give a 1 dB output. |
i have to correct you fig. when educating people you have to make sure you spread the most accurate information. this is a slight correction but i think it's very important.
your example is only true if you rise above the threshold by 2dB. inputing 2dB will not cause any compression unless the parameters are set for that. so, every 2dB rise above the thrshold the compress will output only 1dB, hence 2:1.
so, ratio is based solely on audio rising above the threshold
the attack time tells the compressor that once the threshold has been exceeded exactly when the compressor begins to actually compress. the release knob tells the compressor when to "let go"
you also need to note that ratio, attack and release are parameters that are not always present on every single make and model of compressor and some comps have variable ratio based on how much you have exceeded the threshold (vari-mu comps).
Post by: A.J. on December 09, 2005, 12:50:03 pm
I think this link was posted somewhere in these forums a while back, but it may come in handy for you:
http://www.dbxpro.com/literature.htm
scroll down to white papers and get the Compression 101 pdf. It's a great little pamphlet to help you understand compression.
Post by: Fig on December 09, 2005, 12:56:58 pm
My bad. No compression occurs (ie: a 1:1 ratio, or unity gain) below threshold.
Make-up gain is still active below threshold, however - so DO be careful out there.
Fig
Post by: George_ on December 09, 2005, 02:14:50 pm
| Quote: |
However, sometimes one will choose to compress and NOT adjust make-up gain, instead trying to "knock down" the peaks. Does that help at all? Warm analog regards, Fig |
yes sir:)that helped much!
cold digital ITB regards;)
cheers George
| Quote: |
so let's say you put a kick drum to a comp. you set ti all up to something you like, but the gain reduction meter is showing you -6 of compression on the kick drum. you love the tone you got, but now the kick drum is 6dB quieter coming back to the console. you grab your "make-up gain" knob and simply make up the difference of that 6dB. the output make-up gain is to simply get you back to where yous started. you can use it however you like.....make it louder, quieter....whatever. but don't think of it as a "uncompression" knob. |
thanx J.. things are becoming much clearer now:) sorry for my stupid question.. I read a lot of books and read along the internet, but the last time I turned my virtual knobs I was not shure what I am doing;) so I wanted to correct this.
| Quote: |
I think this link was posted somewhere in these forums a while back, but it may come in handy for you: http://www.dbxpro.com/literature.htm scroll down to white papers and get the Compression 101 pdf. It's a great little pamphlet to help you understand compression. |
will read it tomorrow. I am a littlebit tired for literatur now;)
thanx anyway A.J.!
thanx a lot guys