It seems that some receivers allow calibration of front L/R speaker output levels via independently adjustable +/- dB level (i.e., -10 dB to +10 dB), whereas others allow adjustment via L/R balance control (knob or electronic "slider"). I have a Pioneer VSX-811S that does the former, and a Sony DA4ES that does the latter. So...on the 4ES and others with similar L/R balance controls, when I slide the balance control towards one side (let's say left speaker), is the receiver increasing the output level of the left speaker, decreasing the output level of the right speaker, or a little of both when the control is moved towards the left? And no, I don't have access to two SPL meters so I can't easily determine if adjusting the front speaker level controls is increasing and/or decreasing the front speaker outputs simultaneously. In summary--why the two different types of L/R front speaker adjustment methods? Is one type necessarily preferable to the other?