Master buss compression - what's the point?

[David Polich]

I've been working with the Stillwell "Bombardier" compressor
lately and have been very impressed with it. It does sound nice
on a master buss.

However, even though I've been reading for ages about the use
of a master buss compressor, I have yet to come up with a
reason to actually do so. Wouldn't it always be better to
put a master compressor on in mastering? And wouldn't it be
the exact same thing as putting it on a mix bus?

I would think that most mastering engineers would not want you
to run the mix through a master compressor of any kind.

[KEVORKIAN]

I tend to agree with you.

I love compressing busses/subgroups. Love me some parallel compression on busses but I have yet to hear a master bus compressor strapped across an entire mix that I truly like and think is important. (I've mixed on some nice SSL's in NYC, in some great rooms and honestly never thought the buss comp was helping while on the entire mix).

Some of the history of the practice is likely program/genre dependent.
Some of it is engineers looking for a crutch or a leg up.
Some of it is Legend.
Some of it is tonal.

I'm not sure what people are really after with it though. I also think that the current loudness war actually hurts the effectiveness of such a practice. I wasn't there, but I would assume that the use of a master bus comp on many classic rock recordings would have helped greatly, judging by the uncompressed source material and more generalized mic placement practices. Now a days, with so much specificity, signal gain and compression on the tracks themselves, there is so much less for a buss compressor to really do.

If you look/ask around, you also see that a lot of people who swear by master bus compression are just barely touching the mix with their compression settings. When you factor in the use of a hardware buss comp, then the benefit may be akin to something like external summing (where the analog hardware makes a tonal impact), which, it true, would make master bus compression in the box pretty much irrelevant at this point.

[KEVORKIAN]

I'm not a mastering engineer, but I don't prefer a single compressor across an entire mix even when I do make a master. I like parallel-compression techniques, multi-band comps and limiters (man, I love a good limiter... they are like a good whisky, smooth and to the point).

[bongo_x]

For people who use it, like myself, It is the sound of the mix. You don’t do a mix you like and then put a compressor on it, at that point maybe you should just let the mastering guy do it. I put it on at the beginning of the mix and mix into it. This is the way I learned.

I don’t use it as a utility. It’s part of the sound, the “glue". If I turn it off it becomes a different mix, if I decide I don’t like it I have to replace it and start over, or at least adjust. If you already have a mix and then put a buss compressor on it you probably won’t be that impressed. You already had a mix you liked, right? It’s going to change with the compressor.

Depending on the material I’ll have totally different things happening. Maybe barely hitting it with a high ratio, hitting it hard with a low ratio, attack, release, knee, all different. It gets adjusted all during the mix. And there may be more than one.

I’ve probably never done a mix without a buss compressor, I don’t really know anyone that has, except in rare cases. I know because the some people have mentioned it to me when they have as an oddity.

When you give your mix to the mastering guy, or do it yourself, the point is not to change the character of the mix. The ME is not going to put a put a compressor on there that changes the whole mix, assuming you would have done that if you wanted it, and at that point it doesn’t really do the same thing.

I do find that most software compressors rarely have the the settings in presets that I would ever use. Then again, the idea of compressor presets is about as silly as EQ presets.

bb

[KEVORKIAN]

I don’t use it as a utility. It’s part of the sound, the “glue". If I turn it off it becomes a different mix, if I decide I don’t like it I have to replace it and start over, or at least adjust. If you already have a mix and then put a buss compressor on it you probably won’t be that impressed. You already had a mix you liked, right? It’s going to change with the compressor.
bb

Just to interject regarding my comments. I was talking about using the bus compressor throughout the entire mix just as you describe. Not using it on an established mix as an effect.

In enough instances, I have heard behaviors and artifacts during the mix that resulted from master bus compression that I didn't find favorable (in some cases these settings were created and implemented by more experienced engineers than i). In these cases, turning off master buss compression was the fix.

I'll have to give it another shot soon when I have time.

Are you using hardware or a plugin for your master bus and in either case, what general settings do you prefer for rock material?

[bongo_x]

If I’m in the box I use software (because I’m lazy), in a studio I use hardware.

It all really depends on the material. Of course I have starting points, but there’s no way a any settings are going to work for different things. If I’m doing a rock mix I’ll start with the Sonalksis on with 45ms att, 60,90,150 release depending on the tempo and song, 3:1 ratio, 90 crush, the wide mid sidechain, and about −3 reduction. I’ll see how that’s working and figure out where to go from there.

Different compressors are going to react differently to the attack and release times, and everything else actually. That’s why they’re different.

Compressors can be a difficult thing to learn to use to get the results you want. There can be a lot of subtlety involved, and using one on the mix takes a little more work or experience than on a vocal or other single track. Are you trying to bring down the peaks of the hits, or open them up? Smooth out the whole mix, or make it pop? I might have one barely touching the peaks with a high ratio and quick attack to level the hits, the another after with a slow attack hitting a little harder to glue the whole thing and make it pop a little.

I’m always going to hear the compressor. There are those who think a compressor is great because “you can’t even hear it”. Except in rare cases I’m not one of those, I want to hear it. You have to be careful when comparing it in bypass to have as close an apparent volume as possible to be able to judge the effect. It’s usually going to “open up” when you take it off, but does it sound more like you want the finished product to sound?

My overall point is that the mix compression is not at all the same as mastering for me, it’s more sound shaping, where the mastering is polishing. I tried the Bombadier and it was very nice, but too subtle for what I do. I should probably try it again. When I used that I did feel like I was doing the mastering guy’s job. To give some perspective, I never, except in emergencies, EQ the master. In that case there is something big wrong with the mix, or something subtle that the mastering guy can fix it better than I can.

I don’t think you have to compress the mix, there’s no one way to do anything. It’s just a good tool in your kit to know how to use.

bb

[KEVORKIAN]

It all really depends on the material. Of course I have starting points, but there’s no way a any settings are going to work for different things. If I’m doing a rock mix I’ll start with the Sonalksis on with 45ms att, 60,90,150 release depending on the tempo and song, 3:1 ratio, 90 crush, the wide mid sidechain, and about −3 reduction. I’ll see how that’s working and figure out where to go from there.

Cool. Thanks for going through some example settings. I'll download a demo of the Sonalksis since I don't use that comp and see how your settings compare to what I would be likely to do. Maybe, see what ballpark I'm in.

Compressors can be a difficult thing to learn to use to get the results you want. There can be a lot of subtlety involved, and using one on the mix takes a little more work or experience than on a vocal or other single track. Are you trying to bring down the peaks of the hits, or open them up? Smooth out the whole mix, or make it pop? I might have one barely touching the peaks with a high ratio and quick attack to level the hits, the another after with a slow attack hitting a little harder to glue the whole thing and make it pop a little.
bb

To a degree the points you make raise more questions for me: Specifically, are you making mix decisions regarding the master bus compressor's settings in advance of your beginning to mix the track?

For instance are you actively adjusting your master buss comp while mixing to "bring down the peaks" or "open them up" as either of those concepts could involve some aggressively different compressor settings. However, In my travels, it seems like most engineers treat master bus compression as a set-and-forget idea and just strap it across the 2-bus until done; the safest way to do that is to use some pretty light settings...

[bongo_x]

I’m changing it during the mix. Start off with a rough drum blend hitting it to get a ball park where your levels are going to be and attack and release times.

It really depends on how you want to use it. If you like the flavor imparted by a Neve compressor, just the sound of it running through the circuit might be something you like. You might set up it up so it’s hitting a little it and it’s good, no need to mess with it. That’s very common. The settings I listed for the Sonalksis will very likely be the settings I use, only adjusting the threshold. BUT, I don’t mean to imply that those are golden settings and will work for whatever you’re doing. Like EQ, there’s no way to say a certain setting will work, it’s not the nature of the beast. I can say that I usually like to boost 10k on a Pultec on vocal, it’s usually good, but not if it’s too bright already. If my settings aren’t working I dig in and figure it out, I don’t throw the compressor out, unless it’s just not working.

More dramatic tone shaping is going to take more adjusting. The people I learned with use compressors as much or more for tone shaping than level control. You can just ride the fader if you need level control.

This is the sound of records from the 50’s to the 90’s, so I’m used to it, it sounds like records to me. It’s really the sound of lots of small amounts of compression, not one big smash at the end. That would be the sound of our current century.

The thing is, if you don’t make the compression part of the mix, then someone is going to have to make up for it and guess what you wanted during mastering. If they’re really good and can read your mind that’s fine. Except it’s still not the same as mixing into the compressor. They might want to put their fat Neve on it, knowing it would sound great, but it’s making the guitars bury the vocals. I’m not saying your compression should be anything like mastering level, just get the sound where you want it.

bb

[stephentayler]

Many years ago I passed my mixes through a pair of dbx160 (VU) compressors because that was the sound I was after. Then for many years I used the buss compressor on an SSL, because that was the sound I wanted. I was just trusting my ears and my taste, nothing to with second guessing what the mastering engineer might do, or need to do.

And it does actually have an influence on the way I mix. For me it is a vital part of the mixing process and not a way of pre-empting the mastering process. I tend to use whatever I think suits the material.

Cheers

Stephen

[Kubi]

Also, sometimes there simply is no mastering - i.e. demos, roughs for review, film scores, ads, etc.

I do like to have some compression on the mix buss, especially with Bombardier, though more often I'll use it on submixes.

The more I mix the more I find I like to use a lot of instances of subtle compression throughout the mix, from individual tracks, through submixes and groups, to the master buss. Never more than a couple of dB, maybe even less, but in the end signals may go through up to 3, 4 stages of that. I find this can often yield the best of both worlds - large punchy mixes that still breathe.

[David Polich]

Well, I finally finished mixing this 5-song "Blues-and-Tattoos" girl singer project, and went back to my tried-and-true method - strapping Ozone across the Master fader and mixing into that, then removing it before running the final pass. I have to master this project, so it makes sense to me to mix into the maximizer I'll actually be using.

When I open the exported mixes in Peak and put Ozone on it - no surprises.

[mhschmieder]

Yep, a good practice, and one I used to do before Ozone got more demanding with version 4. I look forward to returning to strapping it across the master bus in DP when I get a new computer, as it definitely can help the mix to get some idea up-front of how different multi-band mastering settings might change the intra-instrument balance.

Other than that, I'm not sure why one would use a Master Bus Compressor -- although as others have mentioned, it could be program-dependent. I think it is more often used as a sanity check that a mix is at a stage of worthiness for pre-mastering.