I will continue with digital audio with a post on EQ. EQ, short for equalization is the alteration of particular frequencies of the audio signal in order to balance the overall sound, or change it per personal preference. This is a widely misused and misunderstood term and hence the blog. Most audio players have an EQ option nowadays. Some of them simply have presets where the manufacturer has stored in a value for each frequency and just given the overall curve a title. The curve as it is called is the curve you see when you have set each frequency to a particular db level increasing or decreasing the gain at the frequency. Simply put, you are increasing or decreasing the volume of that particular frequency of sound.
The human ear can hear from 20hz to 20khz, some can hear a bit further but the average person stays within these limits. The whole frequency spectrum can be divided into three basic sections, Bass, Mid and Treble. When you are a little more particular on isolating different aspects, you can categorize them as Low bass, mid bass, upper bass/lower mids, mids, upper mids, treble, upper treble. The equalizer is basically split into several bars or sliders each lying in one of these sections. Depending on the player, the number of bars or sliders increase or decrease. Simple EQ's have just 5,7 or 9 bars. When you want some more control, you can use a player that has more bars/sliders such as Foobar. Professionals use dedicated EQ boxes per channel (left and right) and have 20-30 bars on each channel or even more.
The image shows the equalizer in foobar. Notice how the frequency associated with each bar is written below it. This is usually the norm, and most equalizers will state the frequency below each slider. As you can see frequencies extend all the way from 55hz to 20khz. The reason
you usually dont see very low frequencies (<100>19kzh) on most commercial EQ's are because while most instruments will have some information in those frequencies, they are at a very low level and are usually not audible to the average listener.
Also, the kind of equipment you use is going to determine how well such high or low frequencies are reproduced. Most ppl will find 100hz to be boomy enough for bass and 18kzh piercing enough for treble. The important thing to note here is also the fact that compressed music
formats such as mp3 lose most information in very high or very low frequencies and basically average them out or zero them out. Hence, trying to increase the gain at 20khz for a 128kbps mp3 file will not make any difference since the file itself doesnt have any information
in that frequency.
The best way to find out what each frequency does is to mess around with the gain on each slider. Starting from the lowest, increase the gain all the way, and bring it back all the way and you will observe which aspect of that song or musical piece this enhances or deteriorates.
All sliders are first set at 0 gain, or in the middle. Push them up, and you go in increments of decibel level for that frequency, and vice versa.
This is all too complicated for the casual user thought popular manufacturers, so they got rid of these customizable options, and just put presets on portable players such as the Ipod or Zune. These are usually titled rock/pop/jazz/vocal/bass boost etc etc.
Rock eq basically has a slight bias in bass. This is because most rock music is played with distorted guitars which are heavy on lower mids and mid bass.
Pop eq enhances the mids, brings out the treble a bit more as well, and keeps the bass intact. This is because pop music is usually very vocal centric, has synthesized music which usually have a slight emphasis on treble.
Jazz eq cuts down the treble, pushes the bass forward.
Vocals as it suggests, pushes the mids and upper mids forward
Bass boost, simple enough, simply pumps up the lower end.
My first level of advice, if you have customizable EQ, stay away from presets, customize your own. The golden rule of EQ is to always reduce neighbouring frequencies when you want to enhance a certain frequency. Say you want more bass. Instead of pushing the first few sliders up, lower the remaining sliders down, you lose a bit of volume, but in net effect, you are enhancing bass. The reason for this is that when you add gain to a certain frequency, the software is going
to add gain/volume by amplifying the signal using software. This is going to degrade the sound. The best way to directly experience this, is to push one of the mid frequencies all the way up. You will clearly hear that frequency distort and sound messy.
This is the same reason why you should never use bass boost. Bass boost simply pumps up the gain of the lower frequencies, in effect adding distortion. If you listen closely, if you turn the volume up with bass boost, the music will distort severly. Even though rock and pop eq's will end up doing the same, they do not add so much gain as to distort easily. So you are better off using rock or pop eq if all you have are presets.
As for how to set a customizable EQ. Start with cutting down the mids. The V or U curve is the most commonly used curve. The primary reason for this is because of the equipment that the average person owns. The commercial speakers and stereo systems do not have proper extension at both ends of the frequency spectrum, nor do they output a balanced level across all spectrums. Upper mids and treble are easiest to do, since the power requirement to drive a tweeter is the lowest.In most cases, most average speakers and headphones will simply output the mids and upper mids clearly, and since this is where most instruments and vocals have a major role in, the listener doesnt feel anything is lacking except bass. So they simply turn on bass boost, which boosts the bass, and in effect you just have a loud speaker or headphone which is just distorting the sound. Instead, if you cut down the mids that the speaker/headphone seem most comfortable with, then you get a more balanced sound overall.
The best way to find out is to try bringing down each frequency by a few notches, and find out which bar made the biggest difference for the same -3db decrement. Keep that as your center, or the bottom of the V, and set the V curve accordingly. Say the speakers I use show the most difference in 1.2khz, i set that at what i feel is a comfortable level, say around -4 db. The immediate frequencies on either side will then be set at -3db, the next at -2db and so on.
Note that this isnt a rule or a fool proof practice. Its just a start, and once you start messing around with the EQ yourself, you will find a curve that suits your equipment and your music tastes and your preferences in sound. But EQ can play a very significant role in how good music sounds to your ears, so take the time to set the curve to your liking and you will definitely enjoy music more.
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