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Gear / Technical Help => Ask The Tapers => Topic started by: Rand0mRoll77 on February 19, 2005, 01:10:55 AM

Title: Question about compression/normalization...
Post by: Rand0mRoll77 on February 19, 2005, 01:10:55 AM
Ok so I taped Sage Francis, a hip hop artist, at The Metro in Chicago the other night...I run AT853s>SPCMC6>NJB3 and the tape sounds pretty good the bass isnt very distorted like it sometimes gets when I tape hip hop shows...maybe cause it wasnt too high in the house but the problem is the volume varies so much throughout the tape. I have normalized it but still most tracks are at a pretty weak level. If I normalized the tracks individually it would sound weird and the volume would vary for each song right? He was backed by Sol.Illaquists of Sound on vocals and 2 MPC2000s (drum machines/sample loopers) and a guitarist so sometimes the vocals and insturments are very high but other times like when he does acapellas or the beat is quieter then the volume is very low....

I don't know much about compression, but remember reading a few things about it on this board, woulld it be able to help in this situation?? I have cool edit pro and I was thinking the dynamics processing effect may work but I havent messed around with it....

here is a picture of the wavform......this is before normalization

Title: Re: Question about compression/normalization...
Post by: Brian on February 19, 2005, 01:15:26 AM
compression techniques definitely help "evening out your levels". As a matter of fact much better than normalization. compression works a couple ways but your case you will want to compress so that the softer parts seem louder or closer to the levels of the loud parts.  I could go on and on about different compression techniques but I think i'll turn to google for some good info.  be right back :)

also.  I'd upsample to 192kHz before performing any DSP.  It will help keep any "anomolies" from DSP up in the supersonic frequency range where it is inaudible to the human ear.  also make sure you are in 32-bit float mode.  this all helps makes for better results when performing DSP.

edit: i can see your pic now.  definitely compress.
Title: Re: Question about compression/normalization...
Post by: Rand0mRoll77 on February 19, 2005, 01:22:49 AM
what kind of settings/compression ratio do you think i should use...i dont really know anything about using compression
Title: Re: Question about compression/normalization...
Post by: Brian on February 19, 2005, 01:23:09 AM
alright...check out this site for signal processing basics

http://www.rane.com/note134.html

here is hte bit on compression:

"Compressors are signal processing units used to reduce (compress) the dynamic range of the signal passing through them. The modern use for compressors is to turn down just the loudest signals dynamically. For instance, an input dynamic range of 110 dB might pass through a compressor and exit with a new dynamic range of 70 dB. This clever bit of processing is normally done using a VCA (voltage controlled amplifier) whose gain is determined by a control voltage derived from the input signal. Therefore, whenever the input signal exceeds the threshold point, the control voltage becomes proportional to the signal's dynamic content. This lets the music peaks turn down the gain. Before compressors, a human did this at the mixing board and we called it gain-riding. This person literally turned down the gain anytime it got too loud for the system to handle.

You need to reduce the dynamic range because extreme ranges of dynamic material are very difficult for sound systems to handle. If you turn it up as loud as you want for the average signals, then along comes these huge musical peaks, which are vital to the punch and drama of the music, yet are way too large for the power amps and loudspeakers to handle. Either the power amps clip, or the loudspeakers bottom out (reach their travel limits), or both -- and the system sounds terrible. Or going the other way, if you set the system gain to prevent these overload occurrences, then when things get nice and quiet, and the vocals drop real low, nobody can hear a thing. It's always something. So you buy a compressor.

Using it is quite simple: Set a threshold point, above which everything will be turned down a certain amount, and then select a ratio defining just how much a "certain amount" is. All audio below the threshold point is unaffected and all audio above this point is compressed by the ratio amount. The earlier example of reducing 110 dB to 70 dB requires a ratio setting of 1.6:1 (110/70 = 1.6). The key to understanding compressors is to always think in terms of increasing level changes in dB above the threshold point. A compressor makes these increases smaller. From our example, for every 1.6 dB increase above the threshold point the output only increases 1 dB. In this regard compressors make loud sounds quieter. If the sound gets louder by 1.6 dB and the output only increases by 1 dB, then the loud sound has been made quieter.

Some compressors include attack and release controls. The attack time is the amount of time that passes between the moment the input signal exceeds the threshold and the moment that the gain is actually reduced. The release time is just the opposite -- the amount of time that passes between the moment the input signal drops below the threshold and the moment that the gain is restored. These controls are very difficult to set, and yet once set, rarely need changing. Because of this difficulty, and the terrible sounding consequences of wrong settings, Rane correctly presets these controls to cover a wide variety of music and speech -- one less thing for you to worry about.

System overload is not the only place we find compressors. Another popular use is in the making of sound. For example when used in conjunction with microphones and musical instrument pick-ups, compressors help determine the final timbre (tone) by selectively compressing specific frequencies and waveforms. Common examples are "fattening" drum sounds, increasing guitar sustain, vocal "smoothing," and "bringing up" specific sounds out of the mix, etc. It is quite amazing what a little compression can do. Check your owner's manual for more tips."
Title: Re: Question about compression/normalization...
Post by: Rand0mRoll77 on February 19, 2005, 03:40:47 AM
+ T thanks alot
Title: Re: Question about compression/normalization...
Post by: Rand0mRoll77 on February 20, 2005, 09:14:50 PM
i recorded this from the balcony and the mics were at foot level so occasionally there are some loud claps at the end of songs....if i zoom in really close in cool edit i can delete the claps, is it alright to do this or does it mess up the general time/delay of the whole recording, sometimes i think i notice a lil reverb in the vocals but it might just be the house mix or me being paranoid....if i delete it out on both channels will i be ok?

i should do this before i compress right?