Graphic EQ

August 18th 2011.
The page has been updated little, rewrote the "Changing the sound"-section below to show more situations.

The page has been updated as of May 14th and 15th in order to add som more content about graphic equalizers, and giving more real examples for each of types and applications. Planning to do more !
So, .. //

Hello, whoever you are, to this Graphic Equalizer guide... tips.. advice.. basics .. whatever. I have written what I have thought of and I hope you will find at least a fraction of it useful. There are some other sources in the menu to the left which you can look at too. I don't know if I'm a master at this topic but I do know a few things, and I've been using graphic equalizers, as software too. So, I have tried to put some of my knowledge into text and content.
Intentionally, I have repeated some points a few times because not all readers read through everything.

A graphic equalizer is sometimes called graphic eq although the whole name is rather more used. So what does the term "graphic equalizer" mean? Although most people with all-round knowledge think of a graphic equalizer as a thing used to adjust the frequency response (of an audio system), it is likely so that few people can explain the term's names.

Meaning of the word graphic

The frequency band sliders are in a graphic representation/image of the "equalization"/filtering that is applied.

Meaning of the word equalizer

The term equalizer implies to perform equalization as to compensate for deviations in the frequency response of a signal system. It can of course be used for other reasons than to "equalize".

What are graphic equalizers used to?

It is an multi-band audio filter device and here are some most common purposes;

1. As a multi-band tone control

Used problably for everything, to make the sound "better" or as "hi fi" as possible etc. The most common setting in regards to this is probably lifting the lowest and highest bands, which is probably rather wrong. Just as often as stereo speakers don't reproduve the lowest and highest frequencies, they might just as well have unlinear frequency patterns on other plalces in the audio spectrum.

Application examples: Home and car stereo, before PA amplifier, guitar equalizer pedal.

2. Equalization

This word is also used for other things than what it actually means, to flatten out (equalize) an audio sound system's frequency spectrum irregularities due to acoustic resonance peaks (in phase) or cancellations (out of phase) and/or nonlinear and/or resonant speaker characteristics.

Of course, it could be used when using headphones too, also there to linearize its frequency performance. And there is one interesting aspect though, with headphones compared to speakers. With speakers that have a low range, it will make the lower frequencies also to be felt. With headphones, the physical perception is not there. With expensive stereo headphones that have a low frequency range, the physical impact of the low frequencies is still not there of course, and strictly, it is then not hifi !. It may rather give an unnatural feeling. If you listen to music with very low frequencies, a good example is a large church organ, in reality you will feel it and those of you who have done it know, yes the sound of the low large pipes is indeed felt.
This circumstance could only be solved by using a subwoofer while listening to headphones.

The term equalization is often used as term for using equalizers in audio recording to adapt, change or improve the tone and it can be read about on many web pages and also as "equalization" books. But as long as any use of this term also shows whether it is equalization or use of equalizers then ok.

Application examples of equalization: Home stereo, car stereo, Music PA system.

3. Sound adaption

As mentioned above, a graphic equalizer can be used even if the purpose is not to "equalize" a frequency response, or as a tone control. When stereo equalizers are used, the tone settings can be set to a sound to make it adapt better to a certain environment, or certain situations with background noise, as in a car or a PA used in a crowded place.
Application examples: Car stereo, Speech PA system, supermarket music sound (no bass or treble).

4. Changing the sound, sound optimization, as an audio effect

In some situations a parametric eq should be used in stead, but a graphic can be sufficient many times too, or even simpler.

Changing the sound

Mixing signals with similar spectrums
One example, in a music recording situation, two signals/instruments or sounds may have a similar spectrum. They can be panned apart, but in order to provide mono compability, the signals can be filtered (with an equalizer) in a way so that the spectrums become different. Then, the signals would become better heard as distinct sounds and apart in a mix.

Sound optimization

To optimize the relative loudness of a certain instrument or vocal in a mix, it can be set to be heard better and to be in the "front" of a mix.

As an audio effect

If you set extreme settings on a graphic equalizer, it will become more like an effect, and even more which can be easily done, if you use 2 or even more graphic equalizers in series, and in a stereo equalizer it is easily done. Then the settings may be same for each channel and so doubled so that the maximum difference between bands will be ca 12 or 15dB x 4 => ~ 48-60dB. As if some bands are at lowest settings and the other at the highest.

Here I thought of describing graphic equalizers in two ways, first the various types in different regards and where they are used (applications). And then the other way, the applications and which types that are used there.

Graphic equalizer types

A graphic equalizer could mean a device for any frequency bands, not just audio. But generally, graphic equalizers are all for audio.
There are different types, which can be defined a couple of ways.

Main types - As hardware or software

Either as external units or as circuits in other devices such as in newer stereo or av-receivers where there are usually preset eq-programs and the better can be customized.
As software, it is used for studio recording mostly, there are a lot of these available, both for free and for cost.

The definitions below only refer to hardware equaliers.

Per Number of frequency bands on graphic equalizers

There are probably equalizers for all number of bands but the most common have 3, 5, 6, 7, 9, 10, 11, 12, 15, or 31 bands. Somewhat estimated, the most looked for bands are probably 10, 7, 31 and 15 bands.

10 band equalizers

Audiosource EQ100
Stereo Graphic Equalizer

This number of bands was used mostly on home stereo equalizers that were quite common between the mid 70s until 10-15 years ago. Not so many manufacturers make them today. Good thing about them is that they cover all octaves in the audio spectrum, from 30 to 16kHz.




MXR 10 band graphic eq pedal

MXR 10 band graphic eq pedal

One I saw recently which is selling cheap is the Audiosource eq100 which seems to be a good one. It's a trusted brand, they've made eqs for a long time.

So aren't 10 banders produced today otherwise? Yes, for car audio. Nearly all 10 banders are car equalizers.

An exception, a very popular 10 band eq is a mono eq, used mostly by bass and guitar players and home studio users called MXR 10 band graphic EQ. In the reviews for the MXR 10 there are very good user reviews.

7 and 9 band equalizers

7 and 9 bands have been used on both home stereo equalizers and as today on car equalizers. Typically, the lowest frequency on these is 63 Hz which is not low enough for a hifi system. It is strange, because if 7 bands was once chosen, why didn't they instead make the bands cover the whole audio range, like 30, 80, 250, 700, 2k, 5k and 15k. Usually, for simpler stereos, the lowest bass is already missing and so when the lowest 63Hz-slider is increased the sound becomes bumpy. And why doing 9 band eqs without the lowest ooctave?

15 and 31 band equalizer

Used in audio recording in studios or at home, in PA systems or audio system installations.

Other number of bands

3 band eqs are rather like 3 band tone controls, used on built in preamps on acoustic guitars/basses and a varity of other smaller equipment. 5 and 6 bands are used on smaller car equalizers.
12 bands have been used on home stereo equalizers, made by Technics and others.

Per nr. of channels

Stereo graphic equalizer

Used in home stereo, car stereo, mp3 players (including cell phones), media players, PA equipment or studio recording equipment. And, as the example above, built in to modern receivers as digital equalizers where some home theater receivers also have built-in equalization features.
Generally called stereo equalizer or in stereo systems also hifi equalizer. Stereo means two channels, with the same number of channels each, as 2x7 or 2x10 bands.
Both channels are identical but usually individually controlled.

Mono graphic equalizer

Not generally common but very common for instruments like bass or guitar as EQ pedals, or as racks for PA systems and for studio recording. Sometimes two mono equalizers are used for stereo. Could also be built in instrument amplifiers as like a bass amp eq.

Digital graphic equalizer

The term 'graphic equalizer' has earlier generally implied the use of analog circuits. While digital electronics has become cheaper and more used in the last 20 years, analog equalizers are still the most common. Some digital equalizers are quite cheap and many audio/sound effects processors that are cheap too, also has a graphic EQ among the number of effects. But some users prefer the visual representation of sliders which are also simpler to use, which the cheaper digital equalizers don't have.

Graphic equalizer software

Graphic Equalizer studio

A program I do not yet know anything about. Then there are a lot of other recording programs, some to be used with plugins where there are even more more equalizer plugins.

Media player equalizers

There are many media players and I mention two of the, sofar.

Winamp

Winamp has these frequencies: 60, 170, 310, 600, 1k, 3k, 6k, 12k, 14k and 16kHz. It doesn't have 30Hz which is a must have.

Windows media player

The most common. Better. 31, 62, 125, 250, 500, 500, 1k, 2k, 4k, 8k, 16kHz.

Applications.

Home stereo equalizer / Home audio equalizer

For home stereo systems. Also called just stereo equalizer. The term hifi equalizer can also be seen. Repeated again, they have to start at 30Hz and end up to 16Hz.
For some unknown reason, there seems to be close to no hardware stereo graphic equalizers where each slider controls both channels at the same time.

Car graphic equalizer

Also called car audio equalizer or car stereo equalizer but for the most just car equalizer. Maybe the second most common hardware type. Car audio/stereo equalizers are often not only graphic equalizers since many models include subwoofer outputs and some include subwoofer crossover frequency control and/or parametric controls.

Car amplifier and speakers

The stereo sound in a car is another than in a home stereo. Regular car speakers are smaller and not made to run the low end bass. And without no doubt, with an equalizer in a car, who would not want to boost the bass? So before using a graphic equalizer in a car, the speakers should be replaced if neccessary.
Replacing the speakers will provide more bass and if the bass is then further boosted with an equalizer, it will raise the need for more power from the amplifier. This is because of the non-linear human hearing loudness perception. Because human hearing has lower bass sensivity, bass frequencies need more power to be heard with the same perceived loudness.

DSP Audio .. Signal.. Processor.. Sound

Pioneer DEQ-7600 DIN Digital Signal Processor 15-Band Digital Graphic Equalizer

Larger image of DEQ-7600.

Pioneer DEQ-7600 with a digital signal processor and digital 15-band equalizer ------>
There have been and are are various "DSP Audio Processor" units like the Pioneer deq-9200 for car audio with a mix of various equalizer types together with various effects. It may impress when you first hear it, but after a few minutes you would probably get tired of it and you would get back to simple yet clean no-effect audio. An equalizer used to shape the tone is not an effect. So when these digital processors are used, it is the equalizer in them that is useful. Most "pop"-music is produced with a lot of sound effects already and among the "effects" in some processors are just heavy eq settings that add on the low range. With a programmable equalizer, you may set the values.

Mp3 player graphic equalizer

In many mp3 players if not all that has an equalizer, only 5 bands are available.
For mp3 players with fixed band equalizers, the lowest band is centered at 50 or 60Hz. I call these equalizer values "bumpy sound eq", read about that below too. Many mp3 player users have headphones with limited bass range so for them, they probably don't care that much. For those who value good audio use better headphones with an extended bass range, the lowest bass range cannot be adjusted very well. But there are a few mp3 player manufacturers with a (semi) parametric equalizer in the design.

Studio/recording equalizer

Either stereo or mono equalizers. Usually not for equalization instead it acts as an audio filter. There are many applications where a graphic equalizer can be used but for other purposes than to "equalize" but mainly as the two below.

As a multi band tone control

To shape the tone of various signals/instruments or vocals. First independently for each instrument's or vocal's own tone. A guitarist may use an equalizer pedal with a setting that he or she doesn't change.

As sound effects

For instruments or studio recording, graphic equalizers are used even to the opposite than "equalizing". For the most they are used to improve the sound of an instrument, vocal or mix. They can also be used in sound effects .

Adjusting sounds so they can be mixed together

In terms of sonic compability so that all instruments can be mixed together in a better way, without blending together. Because of that, eq may be applied differently on the instruments for each song.

And this one, should be the most important but very few studio recording people have realized this:

To reference-set the sound of the used studio speakers/monitors that you use. <<----- Read this !!

These settings on the equalizer before the studio amplifier combine equalization and tone shaping.
If you work with recording, you should really want to produce recordings that will have the same tone pattern as super master productions. Actually, yes. Shaping the tone of the speakers/monitors has to be done. How?
Actually, the answer is easy! Pick a few of your old favourite albums that you know well, with a sound that you like. These albums should also be quality productions preferable made by master producers, like Alan Parsons albums or whatever you decide. If you can set an equalizer to make the sound good then you know that your settings are close to reference. Then always have these same eq settings.

Then, if you produce something with this setup that sounds good, then it should sound good also elsewhere, because you have tuned in your tone sound by reference.

PA system equalizer

Used to accomplish as good sound as possible in a live environment. What has to be taken in consideration is if whether it is music, speech or both. In a PA program for both music and speech, an equalizer should be used for speech too.

Instrument equalizers

Graphic equalizers can of course be used to any instruments and they are too. But there are two types of equalizers made specifically for two instruments and so far, can you guess which they are?

Guitar graphic equalizer

They're also called just equalizer pedal, eq pedal, guitar equalizer or guitar eq. The lowest string on electric guitars sounds at about 80 Hz. The lowest band on the most popular guitar equalizer pedals is 100Hz and then typically with 7 bands up to 6.4kHz. The Boss GE-7 pedal is like this.
I think a littler wider range would be useful.

Bass graphic equalizer

Also called bass equalizer or bass eq pedal. The most common basses are 4-string and the low E-string is one octave below guitars, about 40Hz. Because of this, the lowest band on bass equalizers usually works at 50Hz. The Boss GEB-7 pedal has a range from 50Hz but actually up to 10kHz, making the frequency range wider than of the guitar version !

Graphic equalizer settings

A graphic equalizer varies (boost or cut) the signal amplitude for each of several fixed-frequency bands. Usually, the gain is varied between +/- 12 or 15dB. A few can also be switched to a +/- 6dB scale. Some car equalizers may have other gain ranges, like Kenwood kgc 4042a with +/- 18 dB.

Number of bands and frequency range

Graphic equalizers have different number of bands depending on where it is used. In simpler electronics, or in acoustic guitars with built-in microphones, 3 band equalizers are common. Car equalizers have at least 4, 5 or more bands. In cheaper stereo systems, 5 or 7 band equalizers are common and better stereos have at least a 10 band equalizer. For professional use as in a PA or recording studio, 31 or 15 band equalizers are standard.

Equalizer frequencies vs equalizer band

For beginners no question is too dumb! Each frequency band has its center frequency, so a graphic equalizer doesn't affect just the printed frequencies such as 30, 100 etc, which are center frequencies for each "band". But it does affect the center frequency most.

Frequency band interaction

It is rather important how the bands interact with eachother.
An example to clarify, if the sliders for 500Hz and 1kHz on a graphic eq are set both at +5dB. Then the 500Hz band is gained between about 350 to 700Hz and the 1kHz band between about 700Hz to 1.4KHz. Between the two bands, at about 700Hz, both bands gain are summed in a way that for best audio should result in a quite flat response, for a more consistent sounding audio.
Because equalizers have different designs they may sound different. As of the example above, some equalizers will create a relative dip in the frequency response between adjacent bands when boosted equally, and a relative peak inbetween when bands are lowered. Good equalizers have an interpolating design with a filtering that corresponds to the visual setting.

If however, it would be preferred to boost 500Hz and 1kHz respectively and not inbetween, then it is needed to use an equalizer with more bands so that a 700Hz slider would be unchanged. If a flat response between 500 and 1KHz is preferred in such an equalizer, then all three sliders have to be equally boosted.

More bands aren't neccessarily better and bumpy sound equalizers

A good example which is not uncommon to see, 9 band equalizers where the lowest band is designed for 60Hz and then one band for every octave, 125, 250, 500, 1k, 2k, 4k, 8k and 16. Almost the entire audio range. But the lowest audible range is not there.

How many of you did now think anything like "So what who cares".

Bumpy bass = low bass but not low enough also to be felt

When used with in stereo system with good speakers, the important low-bass cannot be adjusted. Instead, when trying to adjust the bass, all you get is a bumpy sound.
Speaking for my self, I would instead actually prefer a shelving bass/treble control with a qualified design. The Kenwood KGC4042a car eq mentioned above, only has 5 bands plus sub, so it makes 6. The sub-frequency can be adjusted between 30-150Hz so it does cover the low bass well. However, the top band is centered at 12.8kHz but I think the low bass is more important.

I once had a 4-band stereo equalizer and since two nephews of mine were playing electric guitar, I thought of giving it to them and first, putting two 1/4" connectors on the unit so that they could use it beween guitar and amplifier. I did that one evening, with simple tools and a horrible soldering iron, being at my mom's! The clever thing with this simple 4-band equalizer, I don't remember the manufacturer and I don't know if they still have it, was that the first 2 bands were in the lower end and the 2 other bands were in the upper range. As a more sophisticated bass/treble control.

So to the point, regardless of number of bands, any graphic equalizer should range from ca 30Hz to 16kHz. For me, a 9 band 60Hz to 16kHz is junk whereas I would instead value a 5 band 30-16kHz equalizer. The average band ratio for such an equalizer would be about 4.806, 30, 144, 693, 3330 and 16005 Hz. Which could be, 30, 150, 700, 3.3 and 16k.

The Mp3 player Equalizer dilemma

Close to all portable mp3 players have 5 band bumpy bass sound equalizers. The lowest band is centered at 50 or 60Hz. Most mp3 player users have headphones with a limited bass range so for them, it probably doesn't matter that much. But for those who use better headphones with an extended bass range, the bass range cannot be adjusted very well. If this is of concern to you, see if there are any players with better eq, or if you can, build a small portable eq yourself!

What do people do ?

For the most, people who use graphic equalizers don't think about equalization, they just set it for an audio they like, depending on what equipment is used. A guy with old Cerwin-Vega speakers would probably gain the bass sliders gently whereas someone else with a new stereo (if it has tape in/out... ) and small grey plastic speakers, would make the settings look like a hammock.

The nerds however...

An equalizer nerd would have at least two equalizers. One for equalization which is then fixed. The other one as the "tone control". If he has more than one pair of spekares, he would have one equalizer for each pair of speakers. Then, he might have more than one equalizer for various music styles. He doesn't care to buy a digital programmable equalizer with memories, he want quantity instead.

Wasnīt that a good idea? Lets make an H2 of that...

**Great tip** - One Eq for equalization and one for tone shaping - That was infact quite a good idea wasn't it - **

If you thought of that you are a nerd, in other people's views. I'd say you're rather devoted. You might be a recording technician, producer or an ambitious home recording musician.

How to set the equalizer as a tone control ?

Tone shaping is funnier so that part first ! But you should have a linear sound/audio system first, right? No, I realize most readers will have just one equalizer. Anyway, how do we know, how to set an equalizer right for the purpose of tone shaping?

The answer is the same as for studio recording so I just copy in the text again.
Pick a few of your old favourite albums that you know well. These albums should also be quality productions preferable made by master producers, like Alan Parsons albums or whatever you decide. If you can set an equalizer to make the sound good then you know that your settings are close to reference. But you would probably change the settings as you listen to something else later so it's a good tip to write your best settings on a paper next to your equalizer.

Equalization and its limitations

As mentioned above, graphic equalizers are probably used more as Super Deluxe tone controls rather than "equalizers". When it comes to equalization, a graphic equalizer with at least 10 bands at 30Hz to 16kHz, may perform a decent "equalization". That's why PA systems use 1/3-octave 2 x 31 band equalizers.
Using 31-band equalizers is the minimum for a graphic equalizer to be used by an experienced sound technician, in order to set the sound.

A graphic equalizer can only perform approximate "equalizations" because in reality, the frequency response deviations of room acoustics resonances, speaker frequency response characteristics or other circumstances are sometimes very irregular or non-linear. Therefore, it can be impossible to smooth out even with a 31-band equalizer.
However, gentle deviations can be reasonably balanced, but talking strictly, not equalized.

A fast way to perform "equalization" requires sophisticated measuring equipment that would first analyze the frequency response. Pink noise can be played through and the noise is recorded with a microphone recording system. The recorded noise is then run through a harmonic analyzer. The obtained frequency response curve is then applied to a multi-band parametric equalizer where also the frequency and q-value (bandwith) can be set for each band. Today this is made cheaper with digital equalizers.

A simpler way to reveal smaller dips and peaks

A sine tone is sweeped throughout the spectrum and even though the human hearing is not linear, any sudden peaks or dips in the frequency response may be heard quite well by listening. The frequency where a peak or dip occurs is then applied to the parametric equalizer.
The speakers may also be somewhat moved to minimize resonances.
In this way, a fairly good equalization can be obtained.

There are digital equalizers or effects processors that perform both graphic and parametric filtering but if an analog equalizer is preferred, there are some equalizers, although few, that are both graphic and parametric in the way that 1, 2 or 3 of all bands are parametric.

Limitations of all equalizers

Above we read some about what can be done with an equalizer and that "equalization" can be somewhat worked out. But, what is it that an equalizer can't do at all?! I tell you. It cannot pay your bills and it cann.. well afterall, it might pay your bills, if you use it professionally. So what can't it do? It cannot walk on the floor. Of course, it's no robot. Now you get mad at me thinking I'm trying to annoy you. Not so. There is a thing it cannot do. Donīt you already know it? How much time would you spend to prove yourself you are smart enough to realize it? Want to know? Well....

It cannot remove the reflections

Although it can lower any frequency's amplitude gained due to in-phase reflections (resonance), it cannot remove the reflections. Reflections can be so short so that it just thickens the sound and by the way, sometimes that may even sound better.
Some PA guys know how to deal with reflections, they use delays to delay the sound. Or in a simpler way, reversing the phase of the audio might help. When there is a low frequency resonance, its almost like very short echoes. Unless phase shifting helps, it can help to find a very short delay in order to avoid resonant low frequency reflections that otherwise last longer.

Graphic vs parametric equalizer

A graphic equalizer can, generally, only be set with different +/- gain for fixed frequency bands.
If the deviations are narrow, irregular in shape or specific frequencies, a parametric equalizer has to be used. A parametric equalizer may have control over just one frequency. If not used for "equalization" then it is used as a filter for various reasons. Parametric equalizers are common for car audio and for musical instruments and in studio recording.