Thanks for the answer - If we have 3 controls as Bass, Mid and Treble. If we keep those in 12 O Clock position, will the output level be equal. In using the Bass and Treble control only (if we have only two controls as Bass and Treble), controlling these knobs will affect the mid range adjustment - meaning will the relative Mid range frequencies be increased or decreased.

Depending on the design of the amplifier, Bass could be in the range of 20Hz to 200Hz, Mid Range could be between 400Hz to 2. 5KHz and Treble could be in the range of 5KHz to15-20KHz. When you adjust the Bass and Treble the Mid Range should not be effected, unless the amplifier tone filter has a broad band width. Keep in mind, what we hear is a derivative of many frequencies called harmonics. This means an instrument or vocal is not one frequency. It is a combination of many frequencies, which could be in the Low, Mid and High range. There is no easy way to answer this question because of the amount of variables, which exists. The variables are; amplifier design, speaker types and room acoustics. The amplifier has an electronic filter which will limit or boost a specific range of the frequencies in the audible sound spectrum approximately 20Hz to 20KHz. The speakers have a Cross Over which separates the Bass, Mid Range and High frequencies to the Woofer Mid Range and Tweeter speakers which could affect your frequency response. The Room Acoustics could absorb audio frequencies in furniture and curtains or echo of the walls. The most effective way to adjust your sound system is to use an audio spectrum analyzer and play white noise (all audio frequencies at the same amplitude) which sounds like static. Using the spectrum analyzer the visual graph of the white noise should be equal at the same amplitude throughout the audio spectrum. If it is not then you should adjust the equalizer ( Bass, Mid Range and Treble) to boost or limit the sound in that spectrum range. However, two or three adjustments will not adjust your sound system perfectly. You will need a parametric or graphic equalizer to archive optimum results. Once you have adjusted your system you will hear music how the audio engineers and musicians intended it to be heard. I hope I did not confuse you and did not over answer your question. However, I wanted to explain the adjustments so you can appreciate your sound system more than just adjusting the audio for your personal preference.

If all are in 12 o'clock position they are "flat" (nothing has been added or subtracted foam input signal) If you only have bass & treble, yes adjusting will affect "mids" but Mids change can go both ways dependent on increase or decrease of Bass and /or treble. By increasing bass you will pull some mids up also. By increasing treble you'll subtract some mids.