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Better Sound Through Science.
 

Drew's Equalizer And Frequency Equalization Tutorial

The More You know, The Better It Sounds.

First a word about Fundamental Frequencies and Harmonics. Musical 'notes' are made up of fundamental tones (frequencies) and harmonics. It's the harmonics that allow you to know the difference between one instrument and another.

Of course if you strike a string like a piano (yes it is a percussion instrument), pluck a guitar, or draw a bow over a cello, you'll have additional clues to work with.
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But we perceive the notes on a musical instrument or sung by a vocalist by combining fundamental and harmonic tones. And like other perceptions, we actually construct the combination of sounds in our brains.

When we hear a note like middle A on a piano, a complex set of oscillations are transmitted through the air to our ears. The lowest frequency is the fundamental. In the case of middle A for example, it's 440 Hertz. And the higher related frequencies, the harmonics, of 880, 1320, 1760, 2200hz complete the musical sound we hear.

But it's the fundamental that what we call the actual note. And when you use a tone generator or test disc to generate a sine wave of say 440hz, it's the fundamental note alone without harmonics.
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Of course music is composed of thousands of frequencies all sounding at once. But that doesn't change the fact that it's composed of individual tones. So for understanding, it's much easier to look at the frequencies one at a time. Looking at one 'note' at a time doesn't change the equation, it just makes it easier for us to look at it and understand it.

Now On To The Musical Spectrum

The Approximate Frequency Ranges chart below displays the frequencies generated by some familiar musical instruments (including our voices) with BOTH the numerical fundamental and harmonic approximate frequencies shown.

Given the often-talked-about musical range of 20hz-20khz, it is surprising to see just how low the musical fundamental frequencies actually are (almost all are under 3,500khz). But remember, it needs to be understood that if all instruments were perceived only by their fundamental frequency outputs, they would all sound alike. It is the harmonics that give each individual instrument its character, or timbre, and set it apart from all the rest.

Interestingly, the human ear is more sensitive to certain octaves in the musical spectrum than to others. The ear is tuned more toward the midrange frequencies, where speech and voice communication occur (I guess we're still cave people), than to the outer octaves of low bass and high frequency musical harmonics.

As a result, very small energy changes in the midrange frequencies cause much more noticeable effects than do larger changes in the very low and/or very high frequency ranges.

So what is bass? What is treble? Oh, and what about midrange? Let's break them down right here.
My chart above shows the approximate frequency ranges of various musical instruments and the human voice. The black boxes represent their fundamental frequencies and the yellow boxes represent their harmonic frequencies. It's much easier to understand and enhance the instruments you want to hear when you know what frequencies they cover.
 
 
Bass
(Approximately 20hz-140hz)
There is little musical material with fundamental frequencies below 60hz. What is normally perceived as low bass material is actually in the 60hz-140hz range. Only a few instruments actually reach this range such as the organ, contrabassoon and string bass.

The 60hz-90hz range is where we notice the greatest perceptible changes in "bass response." Try a test tone and see just how well you hear 20hz or even 32hz, compared with the same volume of 60hz or 90hz.
Mid-Bass
(Approximately 140hz-400hz)
Mid bass has lots of instruments included in its frequency range. Cello (my instrument), Bassoon, French Horn (Freedom Horn this year) and yes Male Voice are all here. This is where most 'bass' controls really muck up your music. Overemphasizing the mid-bass range gives the music a muddy, or "boomy" quality. If the mid-bass region is underemphasized, the music sounds hollow and thin.

Midrange
(Approximately 400hz-2.6khz)
Since our ears are most sensitive to midrange frequencies, midrange has the greatest effect on the overall sound of your stereo system. Actually there is controversy among engineers and audiophiles as to what the proper balance should be in this range. Some settings are best suited to particular types of music.

The "proper" settings are the ones most pleasing to you the listener. I won't list instruments here because virtually all instruments have fundamentals found here in the midrange with the exception of Contra Bassoons, Bass Tuba and a very few others.


Upper Midrange
(Approximately 2.6khz-5.2khz)
Except for the pipe organ and piano, not many instruments have fundamental frequencies this high. Well, I guess the violin does touch into the range. But, it's really amazing just how little fundamental frequency material actually starts above what we consider midrange.

Speaker designers often boost output in this range to affect the quality or "presence" of the music. Too much energy, on the other hand, sounds overbearingly harsh and strident. A good balance between this frequency range and the midrange frequencies gives the most pleasing sound.

High End
(Approximately 5.2khz-20khz - Two Regions)
The region from about 5.2khz up to about 12khz is normally perceived to be the high-frequency range. (The dreaded treble control.) Only the pipe organ actually contributes any fundamental frequencies in this spectrum (as well as a few others such as the flute), but this is where the harmonics really enhance your musical enjoyment. It's this range that affects the brilliance of music. Overemphasizing these frequencies gives an unpleasant, harsh and even piercing quality to your music.

The final region, the super high frequencies, from about 12khz-20khz, actually contains very little musical material despite all the editorial coverage it receives. However, many very soft 2nd and 3rd order harmonics do reach into this area.

Plus, most adults can hear only subtle differences when adjustments are made in the 14khz-20khz range. It's important to remember that adults, (mainly men) simply can't hear much above 15-16,000hz after the age of 50. So, this area primarily adds a little more dimension to your sound.

Now a word about Graphic Equalizers and what they can do with your frequencies.
 
The Truth About Graphic Equalizers

This is not an ad. It is an explanation of all graphic equalizers. It is not an attempt to promote equalizers sold by DAK over any others. It is meant solely to give you a thorough understanding of what an equalizer can do for your home, car and portable stereo systems.

What It Is. Please Read This Section.
An equalizer is really just a series of 10 or 12 volume controls. The difference between your main system volume and an equalizer's volume controls is that each equalizer volume control affects only ONE area of the whole frequency spectrum.

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Bass and treble controls can't help because they indiscriminately boost everything from the midrange down or from the midrange up. Each actually affects about 30% of the entire frequency spectrum.

So, if you slide up the 32hz volume control on an equalizer, only sounds in the 25hz to 40hz like a string bass are really increased. Why is this important?

Well, the human ear can hear frequencies from about 20hz (20 cycles or vibrations per second) all the way to 20,000hz. Your stereo system, to a greater or lesser degree, produces these sounds.

But for a number of reasons, your stereo system and mine are unsuccessful. An equalizer simply helps your stereo system accurately reproduce the entire frequency spectrum of your music.

If your low bass is down 3 to 6db, you'll miss the excitement, warmth and fullness of a strong bass, a kettle drum or the lower registers of a cello. By increasing the signal with an equalizer, you're not magically creating something that doesn't exist, you're simply reviving inadequate recording or reproduction.

The same is true of the high end. The gentle sound of brushes on a cymbal, or the dramatic sound of glass shattering can be lost if the high end of your music is not reproduced at the same level as the midrange.

Why Aren't Our Stereo Systems Perfect?
The plain bare fact is that virtually all systems and sources are flawed. FM reception suffers from FM preemphasis which causes the FM station to cut back on the high frequencies they broadcast.

Try boosting the 8,000hz and 16,000hz to restore the impact and openness.
While the low frequencies aren't a problem with the FM broadcast, when you or they play records and tapes instead of CDs they are a problem.

Low bass sounds are massive. That's why woofers are the biggest speakers in your system. If recording engineers don't cut back the level of the bass on records, your stylus simply can't follow the groove. And, I don't even want to talk about cassettes.

But What About CD's?
With a CD, you can, for the most part, forget the limitations on your source material. Of course, they have the capability to accurately reproduce the entire 20hz to 20,000hz flawlessly.
But there are two things you should know. If they were made from analog (not digital masters), they may need help (see The Truth About CDs - What's DDD? Below).

And don't forget, everything about your system, your speakers, and your room is even more important than the source. Read on.

The Truth about CDs - What's DDD?
Pick up any CD in your library. On most new discs today you'll see the DDD symbol. OK, all CDs end with D. But there the similarity ends. Read on.

The first D stands for digital recording. This means that the recording engineer recorded all the instruments using sophisticated digital equipment. Not analog mastering. So, that leaves out all of our Golden Oldies, all the old classical favorites and well, Elvis and most Musicals as well.

The Second D represents digital mixing. Engineers mix the masters using analog or digital boards. This of course means no added hum or noise if you see the second D.

The third D is the reproduction media, and since it's a CD, it's always D. So, you can have CDs that are AAD, ADD, or DAD. An audio cassette or LP would usually be AAA. Oh, A always stands for analog.

More Problems
The Biggest Problem

OK, here we are. The important 'stuff.' The biggest problem with your stereo system is probably your room. Speakers placed in corners tend to boom at 125hz.

If they're in a bookcase, they tend to lack bass. Most speakers should be placed up to a foot from the wall to avoid standing waves.

But, which of us can have an ideal room built for our stereos? This is what I do for a living, and I have one speaker in front of a window and another in front of a wall. There's a measurable and 'hearable' difference when the drapes are opened or closed.

So with the aid of an equalizer, you can make your room ideal. You can compensate for a 125hz boom, or for a loss of high end because of drapes or couches.

Listen to the music, then switch in your equalizer. The results will be awesome and repeatable. And that's a good thing.

Plus, it's the same in cars. Typically, they don't have a good high end. If you boost the signal at 8,000hz and 16,000hz in the house as much as in the car, you'll hear really raspy sound.

Studios have to produce their CDs for average home systems. And you know the story about the statistician who drowned in a lake with an average depth of 7". You can custom tailor CDs you make for the weaknesses of various systems.

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An equalizer is the single most demonstrable stereo component you can buy.

Don't be intimidated. You don't have to keep your system flat, I don't. I'm a cellist and I'm used to a stronger bass.

THE OLD AGE PROBLEM
And here's some bad news for you. If you're like me, I'm going to be 57 !!!!! this year (horrors) your ears are no longer as sensitive above 14,000hz to 16,000hz.

So, even if your source is perfect, even if your system is perfect, even if the room is perfect, you may not be.
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Because I work with high sounds (not loud ones) so much, I'm still able to hear 16,000hz to 17,000hz but I guarantee you by the time I turn 70, I'll be cranking up the 8,000hz and 16,000hz controls.

And this is important. It's not really that you can't hear the high frequencies.  It's that you can't hear them as well. So, when you were 30 you didn't need to turn up the 16,000hz slider, now you do. By making the highs LOUDER, you bring back the sound you used to hear.
Please, I don't want to hear from the FDA, this isn't a medical device. But ask your doctor, he'll give you the bad news.

I guess someday I'll be reviewing equalizers for the geriatric crowd with a line like, "If you're 82 like I am, you probably haven't heard a cymbal crash in years…"

Anyway, if you'd like to experience the trumpets crashing out of your speakers, add a boost at 250hz and 500hz. If a female vocalist sounds raspy, cut the 1,000hz and 2,000hz sliders. Or if you want your walls to quiver with the pluck of a string bass or the blast of a bass tuba, boost the 31hz and 63hz controls.

When you switch in an equalizer you'll hear an earthshaking, spine tingling improvement in your stereo system's sound.

Oh yes, in addition to restoring impact and drama to your music, you can easily adjust all the frequency bands to increase dramatic intensity, excitement and openness. Nobody ever said that flat was perfect, it's just a starting point. And, that's the way it is. I hope this Equalizer and Frequency Equalization Tutorial was helpful.

Enjoy. . . Drew


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