Wednesday, May 22, 2013

Multiband Limiting To A Loudness Curve & NS10s


This is a mini tutorial that will attempt to explain the fletcher-munson loudness curve to get a better sounding mix.

Things you should know before we start:

1. Human hearing is not flat. Our monitoring system may be flat, but our ears aren't. The human ear canal resonates around 3k. We perceive sound between 1k and 5k as louder than it really is. Sound in this range can become painful when we turn our speakers up. This is the same range that guitars are played in.

Already knowing this will help us get better mix translation. We know not to boost sound in this area too much.

2. Humans have trouble hearing at extreme ends of the spectrum (at low volume) We can't hear treble past 10k as well as we think. We can't hear bass as well as we think either. We like to boost our stereo. BUT....

3. How we perceive sound changes at different volumes.

The large upward bass curve represents what we can't hear well. The lowest sections on the curve is what "sticks out" to us. The louder music gets (higher up on the graph), the better we can hear bass. The curve gets flatter.

If your music is meant to be played on a club system or stadium, it doesn't need as much bass boost as you'd think. Notice the top curves are flatter. That means we have no trouble hearing it. Mixing on a flatter curve could encourage the listener to crank up your music, if you desire that. Also remember that people have EQ'd their sound systems themselves. This adds a monkey wrench to the situation. Since we can't know or rely on these different systems its up to the mix engineer to use the loudness curve (and consider dynamic range).

Now on to the multiband limiter.

Limiters allow you to change audio gain for custom bands. (Top graphic). Before limiting, You may want to decrease 2k to 6k bands by as much as 10db. This can be done with the gain knob. You can also increase the bass & treble range. Since I want to play my music loud, I might only boost bass by 3.5db. However if my bass kick is already loud I will leave it alone. At this point I'm not trying to get a competitively loud mix. Adjusting the mixer is probably better than using the multiband limiter, but we may not have access to that when we master! When I'm done making the mix sound right by approximating my loudness curve, I can try limiting with the main slider (makes the entire signal louder).

Now you should have a better mix!

Why do I use a multi-band limiter instead of EQ? The ones I use don't color my mix like many EQs. They have easy band controls. I can solo each EQ zone I set up. That helps me hear whats going on seperately. Later on, the compression & limiting function can help me shape the bass and the entire mix. I'm killing three birds with one stone. One plugin to mix to the loudness curve. One plugin to compress my bass peaks. One plugin to brickwall limit my volume.

The Yamaha NS10

The reason that Yamaha NS-10 speaker  translates so well is because they have just the right frequency bump in the 1k to 5k range where we can hear just fine alerady. Its a forwardness you don't want to hear at high volume because it causes pain. As a flat playback system the NS-10 is a failure, but when mixing, the exaggerated nature of this range makes a good tool.

Don't have NS10s? Just do the opposite of this tutorial. Bump the 1k to 5k frequency range by 8-10db instead of decreasing it. Ajdust your mix. Just remember to bypass it when you are done mixing!

So why did I bother getting a flat monitoring system? 

1. Good for playback at higher volume. Great for movies & video games.

2. Mixing & mastering at medium to high volumes.

3. The flat response serves purely as mental reference. No second guessing as to what it might be.

So with this knowledge we know that mixing at low volumes could lead to error. However if we add some EQ or loudness on our playback system, we can compensate a little. Even knowing this, the end results should always be checked on a flat system at a higher volume. The multi band limiter's single band gain control might be the right tool to get you there.

Why does Tron 2's soundtrack sound like a loud piece of junk? Perhaps it was mastered at lower volume, on a small system. This caused over compensation. Or perhaps they know not everyone turns up the volume on their junky home DVD system.

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