Q
You mean the pretty pictures on page 105 of the manual are not sufficient?
In layman's terms it is a tone control on steroids. Instead of just boosting or cutting a single frequency as your basic bass and treble controls do, you can modify a much wider range (and really mess up the sound if you aren't careful).
Frequency: Just what its name implies. If you choose 63 Hz, for example, you can increase (+gain) or decrease (-gain or attenuate) the amplitude of that frequency.
It says the frequencies are adjustable in 1/3 octave increments. An octave is a doubling or halving of frequency. If you look at the scale on the bottom of the Frequency plot you see 63 Hz, 125 Hz, 250 Hz etc. 125 Hz is one octave above 63 Hz (close enough for a government job) and 250 Hz is one octave above 125 Hz. Likewise, 125 Hz is one octave below 250 Hz.
Gain: Technically gain means to increase and Attenuate means to decrease. The scale shows a range of -20 dB to + 6 dB. At 0 dB there is no gain and no attenuation. In the negative range, you are decreasing the amplitude of the frequency and in the positive range, you are increasing the amplitude of that frequency. One knob that does both is just called a gain control for simplicity - Negative Gain is Attenuation so no need to have a second control to turn things down.
Q: The 'width' of the frequency band you are working with. If you look carefully at their frequency plot, you will see that it is centered at 1 kHz. So in the example the frequency is 1 kHz. The Q adjustment ranges from .5 to 10. When it is near .5, it will affect only frequencies very near 1 kHz. If it is near 10, it will affect frequencies quite a ways below and above 1 kHz. In the plot you can see that with a high Q (near 10) the range is much larger and frequencies as low as 125 Hz and as high as 8 kHz will be affected (although only very slightly at those extremes).
So what's it all mean? You can adjust various frequencies to counteract the affects of your room or tailor the sound to the way you like it. If the treble is too bright, you can decrease the upper frequencies. If the bass is too low, you can boost the lower frequencies.
