The Main Squeeze

The other day I happened upon a discussion in a live audio forum where a fellow sound engineer posed this question:

“Limiter On Mains?” Does anybody else do this and if so, why or why not and how?

Now, the term he specifically used was “limiting” however, based on his wording, I came to the conclusion that compression/limiting on the LR Master Bus (as a mixing tool) was indeed that to which he was referring.

A few of the responses were adamantly against it, insisting that it took away from the performer’s dynamics. One went as far to say that most of us “live sound” folks frown on it it altogether unless it’s use was for a specific effect. (It was nice to see someone speaking on all of our behalves for a change.) Some openly admitted to using LR Master Bus limiting as a type of overall system protection too. One other lone responder (besides myself) openly admitted to using (multi-band) LR Master Bus compression as an actual mixing tool.

One thing for sure, almost every school of thought on its use was represented!

One question that immediately popped into my mind was this: So why then does almost every digital console today have comp/limiters on both every input and output? Not to mention the wide availability and use of plug-ins!

There was still that question about the LR Master Bus comp/limiter though…

So, if one uses compression and/or limiting in the recording, mixing and/or mastering process, doesn’t it stand to reason that one may use it in a similar way (if not identical) to achieve an equal end result in the live mix relative to to the original recording? I for one both think so and do so.

The following was my response to the original question in the thread “Limiter On The Mains?”

I've been using compression on my live master LR bus for many years. I typically (but not always) will use a 2:1 ratio with a medium-ish attack and a somewhat slower release. Attack and release times will of course vary, depending on the type of music I'm mixing, for sure. Whether I need the kick drum or the bass guitar to drive (push/move) the track/mix will also dictate how I arrive at those final LR settings. I consider obviously audible compression on the LR mix buss as "too much" already though. That's just me. I do find however, that when correctly applied to my mix, it does both tighten and thicken an already well-structured musical mix. I use it as an overall effect, similar to the mastering/finalization process of a recording.

There's nothing quite like the natural sounding dynamic smoothness of a great finished record, I think.

Don't get me wrong though, that's not to say you can't get there without using compression. That's not what I'm saying at all. (I’m answering a question here)

As with all audio equipment however, each piece has it's own unique flavor. Therefore, I believe that there are endless potential combinations and or pieces that will do exactly what you want in this capacity. There is no absolute right or wrong, just either a satisfactory or unsatisfactory end result.

As a note (from experience), inserting a comp on the LR bus may change the sound of your mix too, simply by becoming an addition to the signal path, even without the use of compression. Many of the higher end (and lower end!) analogue comps definitely add a tonal element to the sound. "Personalities" is how I like to refer to them.

One great way to experiment and learn how to use LR master bus compression (or discover that it's not for you at all, for that matter) is to use a favorite board mix as a source, play it back and insert different comps on your mix buss or playback inputs. Start first with a very low ratio, say 2:1.

Adjust the threshold, attack and release times. Listen to how a faster attack time affects your mix, then slow it down and hear what happens. Then bypass the insert altogether and listen to the difference without compression. Repeat the bypass process over and over until you arrive at a satisfactory end result. Use your ears to arrive at a musical setting, not your eyes!

My release time will typically be behind the attack by some amount, say 1/4 to 1/3, relative to attack. But I've also heard a good (broadcast) end result with the attack and release times both straight up at 12 o"clock high, so go figure! It really depends on what you're using as a comp and you want to accomplish sonically.

Try changing the style or type of comp you're using. Try a tube comp, opto-comp, modern, vintage, multi-band, no knobs type, etc.

This is obviously much easier to accomplish in the digital domain, to be sure.It's really worth the effort to experiment, though.

Remember, it's just a tool to be used where and when applicable. Not just because it's the bag or the box...