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How equalizers work - desperately stupid question

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Pastafarian

Mar 4, 2009
26
0
#1
Had a search for this, but couldn't find an exact answer.

I'm trying to understand how equalizers work. On my amp, say, I've got a standard 3-band EQ. It makes sense to me that if, for example, I raise the treble and reduce the bass, then notes played on the treble end of the fingerboard will be more prominent, while lower notes will sound quieter. Am I right so far?

The thing I can't get my head around is why adjusting an EQ affects a single note. If I play one note, then surely there's only one frequency being played - and I can't understand how adjusting bass, mid and treble would affect just that one frequency. Does that make sense? If not, I'll come back and spell out my sheer ignorance in graphic detail...

Thanks in advance for help.
 
#2
In simple terms notes all have what is called fundamentals, that is the frequency of that note if it were a sine wave and that is what your tuned to. But sounds are a little more complex then sine waves obviously, and the reason instruments sound the way they do is because of harmonics and alot of things affect what harmonics are going to be there; strings, string tension, acoustics (or lack of), body wood(s) (if your bass is even made of wood with some of the stuff about nowadays), etc etc, you get my point.

So the treble control of your amp is likely to not really effect any fundamental of any note on your bass, unless your playing a 5 string with a high C or a 6 string or a 14 string or whatever. So all the treble knob will effect is harmonic content, especially of higher notes if my understanding is correct, so it will make higher notes stand out but because it is emphasising their harmonics, not their fundamentals.

So basically the fundamental is the note, and then harmonics are the clanks, clicks, growling noises, woody sounds and such which make your bass sound like your bass. Also if I recall correctly there are harmonics below the notes you play too which is why you can boost your signal at 30hz and have your low E (44hz fundamental) sound bassier, although that might not be to do with harmonics.

There's a useful illustration of where bass fundamentals run out, and some tips about EQ, in the manual for this fine handbuilt amplifier on page 6: [Invalid or Expired Link Removed]
 
#4
Another way to look at it is: every note your bass can play contains a very wide range of frequencies. So, moving any slider on your EQ will have an effect on every note on your bass.
However, cutting a 40Hz slider won't have as much effect on the very highest notes as it does on the lower ones. In other words your original assumption is correct, but only in a very limited sense.
 
#5
Pastafarian said:
...if, for example, I raise the treble and reduce the bass, then notes played on the treble end of the fingerboard will be more prominent, while lower notes will sound quieter. Am I right so far?
Click to expand...

No. All sound is made up of thousands of "partials" or "harmonics" in the audible range. This is true no matter how "low" or "high" the note.

When you apply "equalization," you are emphasizing or deemphasizing the frequencies in which these partials occur. This affects ALL the notes you play. The human ear hears this in terms of tonal characteristics.
 
#6
Although most EQ is "set" at a given frequency which it essentially turns up or down, it also affects some adjacent frequencies.

Here's a made-up example...depending on the amp design, an EQ control labeled "1000" (1 KHZ) might actually affect frequencies from 975 HZ to 1025 HZ. How wide the spread is depends on the amp design.

But at its simplest, EQ is a gain/volume control for individual frequencies.
 
#7
An amp that has a treble and bass control has a two band EQ with a broad slope. That means it affects frequencies outside its center frequency. Treble , Middle and Bass three band EQ with slightly tighter slope. As more controls are added the slopes of the filters get tighter again. A five band EQ could be called low Bass, High Bass, middle, low treble and high treble. The preferable marking is in center frequencies.

Paul
 

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