Well I've zero'd out the acoustic EQ for the Songtowers.
Still don't fully understand the "standing wave" control or the changes it made (which is separate from the traditional EQ).
This is MCACC.
I know when I switched it off it sounded fuller. Pioneer provides zero information other than "controls the effects of standing waves." Leaning towards turning this off too as the frequencies it controls seem way too high to do anything other than color the sound. Does a filter on 239 hz control a standing wave?
When a speaker is put into a room with walls, floor and a ceiling, reflected sounds can cancel or reinforce one another which alter the frequency response. The automated room correction systems in newer AVR attempt to deal with this, with highly variable success.
At higher frequencies, hundreds of small peaks and dips can be measured in the frequency response. Attempts to remove all these small deviations would result in colorations to the sound that may not be desirable. The characteristic sound that makes a particular speaker attractive could be completely lost. Even if the hundreds of small peaks and dips would be adjusted, it would only be correct for a single position in the room. Moving your head just a few inches would require a completely different set of corrections.
At low frequencies, roughly 250 Hz and lower, the picture is different. There are fewer peaks and dips, but they are much larger, and can persist over a much larger portion of the listening area. They are almost always caused by bass sound reflected off of walls, floors, and ceilings adding to or canceling the sound coming directly from the speakers. When reflected sound adds to the direct sound from the speaker, it results in standing wave peaks; and when reflected sound cancels with direct sound from the speaker, it results in standing wave dips.
Dips can't be corrected electronically. Putting out more power at the dip frequency won't help. If the original and reflected waves cancel each other, they will cancel at 1 watt or 1000 watts. If you have major dips in the frequency response you can try repositioning your speakers, particularly the subwoofer. Fortunately, dips in the bass response are typically not that noticeable. When an instrument plays that particular frequency, the bass is lost, but the higher harmonics of the instruments tone are still there. To some degree, your brain will fill in the missing information.
The situation is different for large low frequency standing wave peaks. These peaks are what tend to shake the knick-knacks off the shelves and result in “one-note bass” sound or, even worse, an overall tubby bass sound. Fortunately, this CAN be remedied electronically, and without drastically altering the characteristic sound of your speakers. Typically a room can have 3 (or more) large peaks due to the distance between the front/back walls, left/right walls, and the floor/ceiling.
Your receiver seems to already have 3 notch filters set up at 74, 101, and 239 Hz. The frequencies of these peaks are in the range where I’d expect to see standing wave peaks in a typically sized room. Note that these electronic notch or trap filters are at defined frequencies, are narrow, and attenuate the sound. Was this set up before, by a previous owner, in a different room, or with different speakers?
I’ve heard of too many Salk speaker owners complaining that their receivers’ automated room correction sucked the life out their speakers’ sound. But if your receiver’s room correction is limited to sound below 250 or 300 Hz, you might benefit from it.
