[ddots-l] Re: Graphic versus Other EQ Types
- From: "neville" <neville@xxxxxxxxxxxxxxxx>
- To: <ddots-l@xxxxxxxxxxxxx>
- Date: Tue, 21 Dec 2010 16:04:59 -0500
Thanks much man!
May the peace of God which passes all understanding guard your heart and
mind in Christ Jesus. God bless you!
Music soft sacred and soulful
Website http://www.nevillepeter.com
email neville@xxxxxxxxxxxxxxxx
phone 407-222-4488
-----Original Message-----
From: ddots-l-bounce@xxxxxxxxxxxxx [mailto:ddots-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Chris Smart
Sent: Tuesday, December 21, 2010 1:38 PM
To: ddots-l@xxxxxxxxxxxxx
Subject: [ddots-l] Graphic versus Other EQ Types
Here are some more thoughts on EQ types, starting with those that affect a
more broad frequency range.
High and Low Pass filters (hpf, lpf) allow frequencies above or below a
cut-off frequency to pass through, hence their name. For example, a high
pass filter set to 200HZ, will let everything above that frequency through,
and will drastically attenuate things below that frequency. Note that in
most designs, the cut-off frequency is where things are attenuated by 3dB,
so don't think of the effected area as starting exactly at that point.
HPF and LPF are very useful for, say, getting rid of some lows on guitars or
keyboards, so they don't interfere with the upper bass notes or the bottom
part of the vocals.
Shelving EQ affects a wide range of frequencies, but a lot less drastically
than hpf/lpf. If you want to roll off highs or lows, but not get rid of
them entirely, this is the tool to use. Adjusting the Q parameter on a
shelving EQ specifies the relative steepness of the slope.
An example might be a low frequency shelf that attenuates by around 6dB per
octave.
Parametric EQ (called peak/dip in the Sonitus plug-in), is a tool for very
precise adjustments. Let's compare parametric and graphic EQ types.
On a thirty-one band graphic equaliser, each band covers one third of an
octave. You can work this out from the fact that one octave represents a
doubling
- or halving - of frequency, and there are ten octaves between 20Hz and
20kHz.
What if you want to get more precise than that?
What if, for example, you want to boost slightly around 450HZ but you only
have bands at 400 and 500 HZ? What if you have a spike in the vocals at 3.7K
but only have bands whose center frequencies are
3.1 and 4K? What if the attack of your kick drum is around 3.6K and you want
to boost just that by a couple dB?
Think of each band on a graphical EQ as having a fixed Q parameter or slope
you cannot change. A frequency slider on a graphic EQ affects a fixed range
of frequencies above and below it.
Q represents the shape of the EQ response curve. It's the ratio of the
center frequency to the difference of the upper and lower frequencies that
are being affected.
The upper & lower frequency's are defined as the point where they are 3 dB
different in level than the center frequency.
using a single band of a parametric EQ, Here's an example. If we are
boosting 6 kHz by 12 dB , and the EQ filter curve shows we are boosting at 9
dB at 4 kHz & 8 kHz respectively, we can calculate the Q parameter by doing
the following:
center frequency divided by upper frequency minus lower frequency.
In this case, 6,000 divided by the result of 8,000 minus 4,000 equals 1.5.
Q = 1.5
So, the Q value that represents this particular equalization curve is 1.5.
This is quite a wide range of frequencies.
A more extreme example would be a Q of 0.4, which would span 3 octaves!
If your EQ plug-in describes this as bandwidth, the important thing to
remember is that Q and bandwidth are of inverse proportion. That is, the
higher the bandwidth number, the lower the Q number. The higher the Q
number, the lower the corresponding bandwidth number. You can find formulas
online to convert bandwidth to Q or Q to bandwidth, if you absolutely need
to know.
The good thing is that you don't have to do math like this to get the
results you want, only listen and practice, practice, practice!
1. Solo the track or tracks you are trying to affect. Loop a
problem area if necessary.
2. Turn the gain up or down drastically, at least 10dB.
3. Keep the Q number fairly low to start.
4. Sweep the frequency value around until you get close to your
target area.
5. Narrow the affected frequency band by raising the Q value, and
zero in on the target as precisely as you can.
6. Back the gain adjustment off to get the desired amount of boost
or attenuation.
7. Listen to the affected track or tracks in the mix, to see if
what you just adjusted improved things or made them worse.
If you are used to thinking in terms of musical pitches and
octaves, as found on a keyboard or other instrument, learn the
frequencies of some notes by their HZ value.
Fourth octave A is 440HZ. Double that and you get 5th octave A, 880
HZ. Cut it in half and you get 3rd octave A, 220 HZ. If you
continue halving, you end up at the lowest A on a piano, way down
at 27.5 HZ.
1KHZ is just above 5th octave B natural. Learn to recognize
doublings or halvings of that frequency, just because the numbers
are easier to work with - 1K 2K 4K etc.
Here's a handy chart that shows the frequencies of our notes, and
their wavelengths.
http://www.phy.mtu.edu/~suits/notefreqs.html
General Tips:
1. Keep in mind that a soloed track that sounds full on its own,
probably takes up too much sonic space inside a mix. Things that
sound small on their own can sound perfect in a mix. That massive
guitar sound you love soloed, might totally obscure the vocals in a
crowded mix.
2. You'd be surprised how our brains can fill in missing
frequencies. We can even imagine the fundamental of a note if the
harmonics are all there, but the fundamental is missing!
3. Carving out frequency space for each instrument is one of the
most important aspects of mixing. If panning things to different
stereo positions doesn't clarify things, consider narrowing the
frequency ranges of some instruments, or mirroring some EQ changes.
For example, if one instrument has a lot of midrange, reducing the
midrange on other instruments might carve out some space for
it. You might want to attenuate some frequencies of the hi-hats
where the crispiness of the snare drum is, or roll off some low
thud of the kick drum, so it interferes less with the bass.
Last but not least, this sort of information is out there for the
taking... books on mixing or recording, manuals for the particular
plug-ins you're using, articles in magazines like Mix or Sound on
Sound, discussions in the Cakewalk forums or those at
www.gearsluts.com etc. etc. etc. Wikipedia and Google are your
friends too!
Chris
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