We Stand Corrected

ADDITIONAL FEATURE ARTICLE

April, 2002 "EQUALIZATION" ISSUE

WE STAND CORRECTED

(FEATURING THE KAUFMAN Q CHART)

BY BOB DENNIS

We have a reader out there who is both a home recording musician and an systems engineer for Boeing. He has come up with a very useful equalization chart and has given us permission to publish it

What Is The Kaufman Chart and Why Would We Be Interested?

The Kaufman chart gives the equalization Q values to affect only a limited number of musical half-steps. Sometimes we have that bass or guitar lines where one or two notes are getting lost. With the Q values supplied by this chart we can apply EQ to bring up just one or two pitches, making the part much more hearable. You will need to experiment to find the right center frequency (Electric bass should be between 40 and 160 Hz - Electric Guitar should be between 80 and 320 Hz - you're on your own for other instruments).

Kaufman Q Chart		Bob's "In Practice" Guide
# Half-Steps	Q Value	Easy To Remember Values That Pretty Much Should Work
1	17.3
2	8.7	Try using a Q of about 9.0 to affect only 1 pitch
3	5.8	Try using a Q of about 6.0 to affect 2 pitches
4	4.3	Try using a Q of about 4.5 to affect 3 pitches
5	3.5
6	2.9	Try using a Q of about 3.0 to affect 4 pitches
7	2.5
8	2.0
9	1.9
10	1.7
11	1.5
12	1.4

In the original e-mail I received presented the "formula" for calculating Q values. He was pointing out that the Q values in my Equalization Primer were off for the Q of 1/2 octave. The following is some of the communication I had with him and is probably only of interest if you are good with math. The net result was I should have said a half-octave Q value was 2.9 (rather then 2.8 as published). But don't worry about remixing all of the tunes you used a Q value of 2.8, because, in practice, it doesn't make enough difference to worry about.

The Original Communication

Original Mail:

"I recently came across the article titled, " The Equalization Primer (The Complete Lesson On Getting Started With EQ)" written by Robert Dennis. I wanted to clarify something within the article. The first table shows the Bandwidth values with corresponding Q.

Bandwidth in Octaves, n, can be expressed with the following formula

X = (4*Q^2 + 1)^0.5
n = log base 2 of ((x+1)/(x-1))

Plugging in values of Q will lead to the following:

Q setting	Bandwidth
0.667	2 Octave
1.044	1 1/3 Octave
1.414	1 Octave
2.871	1/2 Octave

The Q setting in the table for 1/2 Octave should read 2.9...

My Answer:

Thank you very much, can I publish this?...

His Response

The reason I did this analysis was because I was interested in filtering out the really piercing vocals that appear (in my voice and most male voices) around 900 Hz. I had no idea how tight to make the filter to reduce these overpowering frequencies. So I found the bandwidth in half steps on my guitar. I graphed the frequencies to get a better idea of where center frequency was at. I found the corresponding Q value and dialed it and the center frequency in on my parameter EQ. Now when I sing , "to carry on," during Come Sail Away by STYX, my monitor does blow my head off.

Below is more BS if you are really interested. Sometimes us engineers go overboard, I know... [see above chart]. Oh yeah, you can publish this material if you would like.

My Answer (in part):

Very Interesting - We used to have a "standard" EQ of -2dB at 800 Hz to clear up the vocal in mastering (c.1964) that never made it into my "recommended frequencies" chart...

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