[cowparsleyman]

Whato

Just thought I bring this to the forum, about compressors, I know there a quite a few members on the forum that know all about these but there also might be some that really might appreciate a little help.

I'm no expert...basically compressors allow one to bring something up in the mix without it sounding distorted and rubbish.

Why are there so many and what are they good for? One can pay loads of wallop for compressors, but really there is no need.

From my experience they DO sound very different, take these 4 examples from Waves (of course they are available from other Vendors, such as UAD, even free versions Molot CCCP Army version? etc.)

UREI 1176
LA 2
Fairchild 670
dbx 160x

I won't go into the scientific stuff about threshold, ratios and make up gain, as that's been explained better elsewhere.

But to my ears/experience: (based on Waves plugins - not the real hardware)
UREI 1176 and LA2a- subtle but good for Vox
Fairchild 670 & dbx 160x - superb for drums

Overall If I had to go for just one it would be the Fairchild, Waves call it the Puigchild wait long enough and it'll appear in the specials page for a handful of $$$ - (such a daft name.)

The really do sound different enough to justify buying them. Most have enough advanced features on them so you can do more later on...

Channel strips are a section of famous mixing desks from manufactureres like Neve or Solid State Logic, they often come with some kind of compressor in, and can be very good indeed, but it comes with all the colouration of sound that the strip brings, which can be a real treat.

I have tried a bunch of others, such as the Magix AM-munition, and AM-Track are really good too for drums. and some free ones , but to be honest they didn't set me on fire. (to my ears)

The other thing about compressors is that the difference is normally VERY subtle, so don't expect huge differences.

....and one more thing (as Columbo would say) don't fall for the 'Louder is Better' mistake.

Hope this helps

cpm

[cowparsleyman]

btw 'on drums' I mean on individual drum tracks, very often looped drums don't need much at all....

[Ramshackles]

To add a bit more detail - all of the compressors you mention are based on different hardware which had different 'topologies' - i.e they each employed a different electronic technique to get the compression effect. They were:

1176 - FET compressor
LA2A - Opto Compressor
670 - Variable Mu compressor
DBX 160 - VCA compressor

These different topologies affects the sound in different ways.

FET  - Uses a jfet transistor(s) to detect peaks above the threshold (and therefore reduce the volume) FET's are fast, so you can get very fast attacks with them. You can get a real punchy sound with this...regularly used on drums, but can be used on anything that needs some bite. Not at all transparent.

Opto - These used photocells to detect when to reduce compression. The light required for the photocells to react was generated by....a light. Basically louder signals made the light glow brighter. Regularly used on vocals and you will hear it on a lot of 60's records, along with the 660, since that is about all that was available then. The LA2A used tubes for its make up gain which gave it just a little harmonic distortion or 'warmth'. Some opt compressors offer ratio control, the LA2A doesn't.
Because of the use of the lightbulb/photocell, it is much less sensitive to transients than a VCA or even a FET - it sees more of an average over time. So it is used more for 'macro dynamics' rather than 'micro dynamics'; i.e not useful on percussive stuff where you want to reduce or enhance that initial snap. It is also very transparent. So you can use it to tighten up a mix as a whole. It is also often used on vocals since these don't tend to have sudden spikes and benefit from the much more transparent sound.

VCA - Very very fast attack and release - really only used to keep huge transients (e.g. percussive stuff) under control. Very linear - gives a hard knee. Super transparent.

Vari Mu - A tube compressor and (I think) pretty much the first compressor design. Here the tubes are used for the actual compression (unlike the LA2A which has tubes for the make up gain stage but used photocells for the compression). So you get a very non-linear, 'smooth' compression. You don't get seperate threshold and ratio controls and unlike the LA2A its not fixed ratio either. Here, the ratio increases as the gain reduction increases. It responds slowly and so is pretty good on the mix bus to add some 'glue'. It won't give you any real 'punch' like the FET and is not ideal for solving serious dynamic issues.


There you have it...the 4 basic types of compressors. Obviously Waves has modelled some specific hardware units which vary in their distortion/noise/freq response aswell. Play around and see what you like.

Your observations are fairly correct except I would say the 1176 is not at all subtle (it even has the 'all buttons in' mode for extreme punch) and I would particularly use the 670 on drums since it won't really respond to the transients.

[cowparsleyman]

Hi Ram

This is the best explanation I've ever seen regarding these comps, thank you very much, a great help, and kind of explains why I use them, I go by how it sounds not the tech.

I've heard about transient shapers, like MAgix AM_pulse and Waves Transx, have you got a Shackles explanation for them too, would be very useful.

cpm