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Lum Tham

Does it make sense to use compressor at master bus

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Dear all,

Goodday.

I watched youtube videos and the application of compressor seems to be limited to only apply as FX on vocals. 

I wonder if it make sense to use compressor on master bus? to smoothen the volume of the entire mix.

 

Thank you

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Compression is also applied to things like drums, (parallel compression), guitars, whatever tracks need taming.  I myself try to use it sparingly.  I purposefully use dynamics in my songs, so not a big fan of compressing at the master bus level.  Others may choose to do it.

Bob Bone

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A limiter is also a compressor. It is most often found on the master bus. 

 

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Multiband compressors are sometimes used lightly on the master, or a limiter, as John points out, but i never use a single band compressor on the master.

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Posted (edited)

It's fairly common to run a compressor over busses, even the master buss. Some people use these as "glue" compressors since it kind of crushes the sound to tame some transients and make it seem thicker, and "glues" the mix together more.

I personally don't like to use single band compressors on the master too much, preferring to use a multiband so I have a bit more flexibility for what frequency area I want to crush, how much attack and release, etc., but I've been in a lot of mastering studios where it's common to use a gentle single band compressor first to "knock the tops off" of the transients before you send that to the final limiter. Running a series of compressors rather than trying to do that all with one set more aggressively can make things sound a lot more natural.

For anything I master here from other clients, though, I'd really recommend hardly any to none on any mixes I'm given. You can't bring back the dynamics on a mix that's been squashed too much, and it's really easy to go too far if you're fairly new to using compressors on the master buss.

Edited by Lord Tim

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5 hours ago, Lum Tham said:

Dear all,

Goodday.

I watched youtube videos and the application of compressor seems to be limited to only apply as FX on vocals. 

You might say there are two ways to use compressor - as an effect or to even out levels.

On guitar you have a nice sound strumming chords and you push your amp in one way, then filling in single notes may become thin. A compressor can remedy that so much weaker power of single notes are lifted in level for a bit.

Some kind of limiter on master is common I think. As said could be seen as compressor with very high ratio, 10 or more.

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Most of the time, I run a normal compressor on the master bus, very gentle settings, a multi-band compressor, again with very gentle settings. Top-down mixing approach says to do this after you get a static mix, and mix through these effects. The limiter comes later, as the very last thing to do.

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5 hours ago, Lum Tham said:

Dear all,

Goodday.

I watched youtube videos and the application of compressor seems to be limited to only apply as FX on vocals. 

I wonder if it make sense to use compressor on master bus? to smoothen the volume of the entire mix.

 

Thank you

As others have said, it's really up to you. You can put a compressor anywhere really. They're all different color crayons in the box, its up to you to make something with them. Some people put them on master buses, some people don't. Personally, I tend to just run a clean limiter on the master bus, but that's just what works for me. Try different ones. See what you like. To borrow a tagline, "if it sounds good, it is good". 

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Many do. What mix engineers do at the Master bus often depends on whether they are attempting to master the music themselves or whether they are preparing it to be mastered by someone else. Another party will likely wish to have the dynamic range preserved.

My mastering chain includes a "soft knee" compressor (currently I'm using Cyclone by Soundspot) right before a limiter.

An important thing to do is to just try it and see what you think. Put on your headphones, put your mix on in loop playback mode, close your eyes, put the compressor on your Master bus and switch it in and out, try different settings, close your eyes and switch it in and out again a few times, see what little differences and details you can notice.

Then you'll have an opinion of your own, and more experience with critical listening. Compressors in general are in my experience the most difficult and most important processors to learn how to use. You need to train your ears to hear what they are doing, what effect the different controls have on everything. Attack, Release, Ratio, Makeup.

When I put a compressor on a bus, it can change the sound of everything in that bus: instrument balance, EQ balance, panning, reverb level, stereo image.

They started out as a device to prevent signals from overloading other devices, like not getting too hot a signal on tape or into a mixing desk, but a funny thing about compression is that our ears have it built in, and if we apply the effect to artificially created sound, we can help make it sound more natural to our ears. As far as I know, this was an unanticipated side effect of using the devices. But that's just one of the things you can do with a compressor.

You can set them up so that they make an instrument or mix pump and breathe in time to the beat, or soften sharp transient sounds or change an entire mix' perceived loudness. In the case of the bus, you can use it to "glue" several different sounds together so that they all sound more coherent, like they belong together. The compressor tricking the ear again.

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Many highly regarded mixers use a compressor on the 2buss.  I use two on mine and a limiter and sometimes  a MB limiter so I guess you can call that 3 or for layers of compression on the Master Buss.

I think where most amateur mixers go wrong is piling too much of it on, it's more like a coat of varnish to add little vibe & thickness not necessarily squash all the dynamics the mix.

Some compressors add a nice tone even if they aren't compressing. So they are more like an effect / fairy dust than a means of level control.

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On the 2-bus I have an SSL Bus Comp set to very fast attack/release times and 2:1 ratio to get a gain reduction of barely 2dB. A bit of glue. I use a true peak limiter  to keep peaks below -4 to -4.5 dB.  

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All the old Sonar programs I have had a "final mix" setting in the standard included compressors. I always assumed they went on the master buss for some gentle taming. I would imagine a mastering house would rather do it themselves but that has never been an option for me ..

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It doesn’t matter,  mastering will do that I the end.  But At one point many proS wouldn’t track or mix without slamming the ssl buss comp on the master.  I don’t use a master buss comp or anything, but I’d be happy to use cakewalks ssl buss comp if I did.  Really nice job on that one.

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Posted (edited)
1 hour ago, Alan Tubbs said:

At one point many proS wouldn’t track or mix without slamming the ssl buss comp on the master.  

If you read any of the articles in SOS from these big name pro producers , there's often compression on the way in when it's recording , then one or two at the track level , then also on the master buss and then it gets mastered.

Edited by Mark Morgon-Shaw

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Master bus compression is pretty much standard practice nowadays. Even in naturalistic genres such as jazz, folk and classical.

But it's only become standard practice in the digital era. While making the transition from analog tape we realized just how much mixing work the tape had been doing for us. Most engineers today are using gentle compression settings that mimic the effect of tape compression. Talking 1.5:1 to 2:1 ratios with slow attack, and 1-3 dB reduction.

Which is good, because overcompression can easily suck the life out of your mix. Unless, of course, you're doing EDM or rap, in which case extreme compression is intrinsic to the genre. But for everything else, including hard rock and metal, do your heavy compression on tracks rather than on the master bus. It's a choice of "making it breathe" versus "letting it breathe".

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Posted (edited)

Every convention we have now was once formed on a "new day" in the past.  Let your ear bring you new days, and put whatever you like wherever you like, based on the audible result and your personal flair.  Heck, compressors across the board can all have different sounds due to varied phasing and frequency responses, so go for what you think sounds great.  It could be a new day.

(For demonstration of what various compressor plugins do to parameters other than compression, try Plugin Doctor.  Load 'em up and see their frequence and phase character, and other things.  It's vegetable soup -- potpourri.

Edited by Jon White

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2 hours ago, bitflipper said:

Master bus compression is pretty much standard practice nowadays. Even in naturalistic genres such as jazz, folk and classical.

But it's only become standard practice in the digital era. While making the transition from analog tape we realized just how much mixing work the tape had been doing for us. Most engineers today are using gentle compression settings that mimic the effect of tape compression. Talking 1.5:1 to 2:1 ratios with slow attack, and 1-3 dB reduction.

Using compressors on the master was often used pre-digital to get more level on vinyl...the loudness wars have been happening for a while :) But Bit's right that these days, it's kind of a given.

Personally, I prefer not to mix with a compressor in the master bus, because then you're depending on the compressor to compensate for what may be lacking  in the mix. Whenever I've tried "top down" mixing (of which I'm not a fan, either), with the compressor bypassed, the mix doesn't sound as good to my ears. 

So you might think "well if it doesn't sound as good, then just leave the dynamics enabled." But I've found that if I optimize the mix with zero dynamics processing, then add dynamics processing as the last step when mastering, the final result sounds better than if it had been done "top down" from the beginning. 

However, I also regard mixing and mastering as separate processes. Once I'm totally happy with the mix,  while mastering (which I do several days later so I can hear the mix with fresh ears), I'll always add some dynamics control.  My current favorites are the Waves L3 Multiband Stereo limiter, which I've been using forever, and more recently IK Multimedia's Stealth limiter (very transparent, but a major CPU hog). Having about 3-6 dB of gain reduction can make a good mix really come alive, and the multiband dynamics sounds much more natural than single-band dynamics processing. (Note that some people want a compressed sound, which is of course perfectly legit, it's just a personal preference that I want my music to sound like there isn't any dynamics processing, even when there is.)

I agree that bus compression on the master can "glue" (whatever that means!) tracks together, but so will adding dynamics as the last step of the process.

Bottom line is if a mix needs dynamics processing, then I feel there's a problem with the  mix. But if the mix likes dynamics processing, then you can take a good mix to the next level.

Finally, if you're giving the mix to a mastering engineer, I recommend not using anything in the master bus. Some "pro" engineers have really raked me over the coals for this, because they say I'm asking the artist not to be true to their vision. My response is I have better toys than they do :) and so do most mastering engineers. I just finished mastering Martha Davis's latest album and bless her heart, she sent me mixes with no dynamics processing. Because of that. I was able to tame some issues in the mix that would have been impossible to fix had the mix been compressed.

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^^^ +1 for Craig's observation about NOT putting the compressor on until you're ready for, or at least close to, the mastering stage. Having it there from the get-go doesn't really do you any favors. In fact, I normally place NO plugins at all on the master while mixing.

To be fair, not everybody agrees with that approach, with some preferring to mix into a compressor all the way. IMO, that's like making a cocktail underwater because you plan to add ice cubes later.

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Posted (edited)

My counter to that is you have no real idea what's going to happen at the master stage if it's the kind of music that will most likely have a fair amount of limiting done to it.

First, I do absolutely agree that if you're planning to send your stuff off to a mastering engineer, let them do their job! Like Craig says, they more than likely have much better toys and far better skills than you do, so don't tie their hands by limiting their options. Take any dynamics effects off of the master unless it's something crucial to the sound of your mix before you send it off.

But with that said ...

If you're doing a style like metal or modern "radio" pop/rock where it's likely going to be hit hard with limiting later (to whatever degree, now that the loudness wars are kind of done) then you need to have an idea of what you're giving the mastering engineer because that can *also* tie their hands. How a mix is going to react to those effects is something you need to keep in mind. Generally you'll find that any bed instruments like rhythm guitars get much louder, cymbals get harsher/washier, you lose the snare or it loses transient definition... lots of things like that.

So how do you deal with that?

One option is to send stems so the mastering engineer can rebalance the mix if things start to get lost.

The other option is to get your mix sounding great with nothing / light compression on your master outs, then strap a fairly aggressive limiter over the master and listen to the changes. You'd want to try to match the loudness levels of the commercial mixes you're aiming to get close to. Do a new mix with that on there, getting it close to what you were originally going for (with that added loudness you'd get from a limited mix) and then *take it off*. It will sound super weird and pokey sounding now, but this will be EXTREMELY dynamic now, giving the mastering engineer huge amounts of headroom to play with for processing later.

Bring both mixes to the mastering session and talk to the engineer about it. I've found the best mastering people will want to work with you to get the best product and will give you guidance about what they need. 

Every style of music will have its own requirements and goals, so don't take what I'm saying as a one size fits all thing. If you're doing acoustic folk, or jazz or something, the chance of this stuff being slammed as hard as a melodic death metal mix is kind of nil, so it's not worth going to this kind of trouble. But it does pay to at least have an idea once your mix goes off, and good communication with your engineer will really get you over the line! :)

 

Edited by Lord Tim
Sending my spelling off to a mastering engineer for fixing 😑

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Good points, Tim. For a long time, although I mixed without anything in the master bus, toward the end I'd always strap on dynamics and squash things to anticipate what would happen when it was mastered. And yes, it can mess with your mix. However, I did find that over time, there was less and less difference in the mix between the unlimited and limited versions, because everything kind of came up by the same amount. Then the LUFS thing hit, and doing too much compression actually made your mixes sound smaller when brought into conformance with LUFS standards.

So...always in motion is the future. What worked yesterday might not work today but might work tomorrow...or what worked today may never work again! I will say, though, that music's (seemingly inevitable) march to streaming has thrown a lot of the old workflows out the window. 

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