Understanding EQ

wahrez

Well-known member
I've been trying to find a simple explanation of how to get a decent mix for ages and came across this on another site and thought I should share it here.

I've just applied some of the techniques (very liberally) to a film I'm working on at the moment and the results are instantaneous!!! Does anyone have any other tips?

Credit goes to a Jon Fairhurst and Jay Rose for the original postings : http://www.dvinfo.net/conf/all-things-audio/73903-eqing-video-film.html

We face the problem that we want our films to have music, foley, effects and dialog, and we need the dialog to be clear, natural and understandable. We also want the music and effects to sound powerful, but not bury the on-screen voices. What to do?

Under 150 Hz
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In this range you can pull down the dialog. It will help reduce plosives, handling noise and echo in large rooms. If the voices get too thin, lower the cutoff frequency.

For music, you can cut things like bass drums a bit at the lowest frequencies (say under 60Hz) to ensure that you have no sub-sonics, and to give you more headroom.

Low cuts are nice for safety, but if you're too aggressive, things get thin. Find the right balance.

150Hz - 300Hz
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This is where the fundamentals of voice and many important instruments exist. I like to give the voices a slight boost and the music/effects/foley a slight cut here. If your voices are boomy, back it off. If thin, boost away.

One trick is to send your music to two sub-busses. When you're underscoring dialog, use the cut version. When standing alone, use the flat version.

300Hz - 600Hz
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This region is less critical for voice. You can boost your music/etc here and get away with it. Cut the voices here to make room.

600Hz - 1200Hz
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This region is critical for consonants. Boost the voices and cut the music. You lose some fast attacks on your music, but it's more important to understand the talent.

1200Hz - 2400Hz
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This area isn't critical for voice. Cut the dialog, boost the music a bit.

2400Hz - 4800Hz
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This region is important for distiguishing voices and instruments. Boost the voices and cut the music - especially if there are multiple voices. The downside is that your oboe will start to sound like a clarinet. You can push this range back up for the music when it stands alone.

4800Hz - 9600Hz
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This is the *sizzle* region. I boost both the music and voice heavily here.

9600Hz and up
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Don't worry about higher frequencies too much. It's mostly noise. If your tracks have HF noise, feel free to cut with a heavy hand.

The overall sound
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I mixed with this technique last weekend for the 48-hour film project. I didn't have time to think about it, so I just threw the above EQ rules at everything, modifying each band by +/-2dB to +/-4dB, being less agressive on the lows and more aggressive on the highs. You can actually be much more aggressive with the cuts and get away with it.

The voices sounded *great*. We used a long shotgun (our best mic) indoors, and the ambience was very natural. It didn't sound boomy, in a cave or anything like that. In fact, it sounded very intimate. It gave the feeling of being very close to the actors in a quiet invironment. You could hear lips, tongue and breath. There was just enough room effect to sound in-place.

The music sounded a bit hollow. This was great for my forelorn score, but wouldn't work in all cases. If this happens, just back off the EQ adjustments to taste. During the swells when there was no dialog, I wish I had gone with a more neutral EQ to give more power, but it wasn't in the time budget.

The bottom line is that I could run music peaks simultaneous with dialog and never lose an ounce of intelligibility.

The other "rules" I used were:
1) Mix nominal dialog so it peaks around -12 dB. Find the loudest normal speech, and set your fader for the -12dB peak goal (ignoring plosives and the odd loud sound).

2) When the dialog is too loud, use an envelope to cut only the offending syllables. This keeps your noise floor consistent between sounds.

3) Copy the dialog track and apply heavy noise reduction. Only mix this in when the dialog is too faint. Mixing this in won't affect the noise floor, and you've still got the unprocessed stuff from the main track in there, so the NR artifacts will remain somewhat hidden. You can be sloppy with the envelope, as there should be little noise between words. For dead syllables, mix up both tracks on just that syllable. (Fortunately, the EQ tricks help avoid dead syllables.)

4) Mix the music as needed. Rather than use compression, mix down the offending instrument or envelope down just the loud hits.

5) When done, especially if you are the composer, mix the overall music down another 2 to 3 dB. No one loves your score as much as you do. ;)

6) Review the whole thing. Envelope the music back up in the dynamic swells, if needed. Step 5 gave us more headroom - let's use it.

7) Check your peaks. The maximum should be about 1.5dB below full scale, just to be safe. You can peak higher on an explosions or gun shots (which are just a loud noises), but not as high on a loud voice or music, which have understandable information.

There are countless other tricks as well - especially if you have a multiband compressor on hand. But we're not mixing the world's loudest CD here. We're mixing for a film. We've got dynamic range. Use it.

In any case, if you're not a professional audio mixer, just go with the above rules, and your DVD print will have understandable dialog, safe levels, room for dynamics and a consistent level of background noise. The result should sound professional.
 
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Nice post Huck. I think that will be of help to many. You might want to post a link to the original work to give those guy's proper credit and traffic...imho.

Cheers
 
I must preface this by saying that I've been making a living as a recording engineer for over 30 years. I've done dozens and dozens of feature films as music scoring mixer, hundreds of pop, jazz and classical albums, more commercials than I care to remember, and countless voice over, foley and ADR sessions...nuff said?

So...please beware of any kind of "recipe" for good sound. Source material variations can make every single recommendation on this list wrong.

A couple stand out in particular:

"1200Hz - 2400Hz
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This area isn't critical for voice. Cut the dialog, boost the music a bit."

Nonsense...complete, utter, off-the-wall rubbish. Am I being clear on this? This frequency range is an absolutely critical one for voice clarity and its ability to cut through other sound, like music and effects.

"9600Hz and up
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Don't worry about higher frequencies too much. It's mostly noise. If your tracks have HF noise, feel free to cut with a heavy hand."

Not as wildly insane as the previous, but still very inadvisable. For starters, the human voice, especially male, covers a very wide frequency spectrum - almost all of it in fact, but more so in the extreme high end than the extreme low end. Routinely rolling off frequencies above 9KHz will make most voices, male and female, sound dull and lo-fi on a high quality playback system. It might be fine on an iPod, but maybe not there either.

It's worth noting that world-class microphone designers spend vast amounts of time and effort refining and extending high frequency response, in substantial part for *just this reason* (voice). It's one of the main reasons top recording studios will routinely pay $10,000+ for some of these mics. A vintage Telefunken ELAM-251, renowned as perhaps the greatest vocal mic ever, can cost well over $20K. It's high end extends beyond 20Khz, and sounds absolutely divine up there. Many top singers and voice talents *exclusively* use mics that have similarly extended high frequency response.

Ok...so getting back down off my high horse here, I don't mean to say that the article is useless. For those with little experience, evidently like the OP, some of it can be helpful. Sound recording, acoustics, and mixing can be very elusive arts. I know - it took me many years to become expert at them.

But again - there is no...let me repeat that...*no* 'recipe' for eq-ing things. You could follow the instructions above and get nice results, or it could simply hammer your audio into oblivion.

Sorry, but like most anything in life worth learning to do well, there is no substitute for actual knowledge of the craft gained by doing it and meaningfully evaluating the results. Then rinse, and repeat until you can reliably produce good work. The solution will be to a very significant degree different almost every time. Believing there's a cookie-cutter approach for something as elusive as great sound is like believing fortune cookies are prophetic.

And yeah...I'm sure I'll catch a whole boatload of flack for this. So be it...
 
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You evil dooer, you mean I can't print a cheat sheet and get a job at Warner?
Ted good points all around. In defense of the cheat sheet, it's better than twirling knobs at random. Other than the big oops in the dialogue zone it should be useful as a general guide for those who are not going to do an audio post. And as much as it pains me (in lost work but also in the theatre experience) to say it there are a fair number of folks who will not do an audio post. Some for reasons that make sense but most because they just don't understand what audio post will do for their films.
 
I found it particularly useful in giving me some idea of what to look for when mixing my films. Thanks for offering some further insight into those frequencies!!

I would love to be able to afford a sound mix but when, as with my most recent project, the budget was approximately £200 it wasn't possible!!!
 
Well I didn't understand a word of it. Wish I did. I need that kind of knowledge.

What does it mean to "pull down the dialogue"?

"It will help reduce plosives, handling noise and echo in large rooms. If the voices get too thin, lower the cutoff frequency." What are 'plosives'? What does it mean if a voice is 'thin'? How do you 'lower the cutoff frequency'?

I guess a crash course in audio engineer terminology is going to be first on my list. :)
 
What does it mean to "pull down the dialogue"?

"It will help reduce plosives, handling noise and echo in large rooms. If the voices get too thin, lower the cutoff frequency." What are 'plosives'? What does it mean if a voice is 'thin'? How do you 'lower the cutoff frequency'?

Well I have no clue about audio, but I'm trying to learn, so correct me if I'm wrong:

  1. Pulling down means pull down the volume.
  2. Plosives are explosives, and can be circumvented by popfilters - 'p' will create a noticeable airflow, that can be heard.
  3. A thin sound is either low or some frequencies are cut.
  4. You may feel that "frequencies for voice recordings below 120 herz don't belong to the voice itself, thus must be noise" so you'd cut off everything below 120 herz.
 
Well I didn't understand a word of it. Wish I did. I need that kind of knowledge.

What does it mean to "pull down the dialogue"?

Just lowering its volume : )

What are 'plosives'?

Consonants like B's and P's that push a lot of air make microphones "pop" when used close up. It's shorthand for "explosive". Hold your hand in front of your mouth and say "bring me the paper" and you'll know exactly why mics have that problem.

What does it mean if a voice is 'thin'?

It means it lacks lower frequency content or has too much upper frequency content, e.g. the opposite of what would be called a "booming" male voice.

How do you 'lower the cutoff frequency'?

The cutoff frequency would be the audio frequency (in Hz or KHz) below or above which the sound is filtered out. If you were filtering out frequencies above 15 KHz to get rid of hiss for example, and it wasn't getting the job done well enough, you might 'lower the cutoff frequency' to 10 KHz. For unwanted low frequencies (rumble, hum and uh...'plosives), you might raise the low frequency cutoff for similar reasons.

I guess a crash course in audio engineer terminology is going to be first on my list. :)

Couldn't hurt. "Modern Recording Techniques" by Robert Runstein has been a long-recommended book on the subject.
 
If you don't have a pop filter handy, a quick and dirty solution that can provide decent results is the use of a #2 pencil (eraser side up) a couple of inches away from the capsule of the mic, between the capsule and the speaker (or singer). The pencil tends to break up the air column and prevents it from maxing out the capsule.

Plosives are really only an issue when the talent is addressing the mic on axis (head on) and fairly close. If you are booming above or below them they won't be blowing into the mic in most cases.
 
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