Originally Posted by jmichaelf
If you haven't already taken a look, Sean Olive over at Harman performed some testing
with different processors and target curves where he discovered that the most favored curve was a fairly inclined slant from gained bass frequencies to attenuated high frequencies. Interesting findings and a good first effort.
Thanks for the link.
Dr. Olive's listening test method states that the responses were normalized to within .1 dB, but I wonder what the test volume was in relation to the levels the content was mixed.
We know that the sensitivity of human hearing decreases in the bass and treble regions as the levels are reduced. Therefore, if the listening room acoustic environment was the same as the mixing acoustic environment, it would require boosting the bass and to a lesser degree the treble to obtain a perceptually flat frequency response when the listening levels are lower than the mixing levels. How much a boost is required for bass and treble for a perceptually flat response will differ depending on how much below the mixing level the content was played. This non-linear hearing phenomena is obvious in reviewing the various equal loudness curves.
However, rarely are the acoustic environments between the mixing room and home listening room the same. In typical home listening environments as the frequency increases speakers become more directive and a roll-off of the high frequencies is usually needed to tame brightness. This needed reduction in the highs probably is greater than the need to slightly boost them when listening at lower levels.
Whereas the Harman listening room does have a bit of acoustic treatments, it nevertheless has a large portion of exposed wood flooring and it is the size of many home listening rooms. Therefore, even though it may have acoustics which are not as lively as most home listening rooms it still has more in common with them than the recording studios. Therefore I believe that a high frequency roll-off is also appropriate for listening in such a room.
So putting this together we may infer that if listening at below the mixing level a listener would prefer a sizable boost in the bass to make up for the decrease in hearing sensitivity and a gentle roll-off in the treble to deal with acoustic differences between the mixing and home listening environments. It is not surprising that a smooth frequency response is preferred connecting this boost in lows to the roll-off in highs.
It should be noted that Audyssey correction now includes a feature called Dynamic EQ that deals with correcting the frequency response to accommodate a reduction in listening levels and it does so in real-time measuring the actual changes in levels throughout the content. Although the Audyssey target curve is flat below 4 kHz, this Dynamic EQ feature alters the response effectively inserting a tilt in the frequency response as the volume is reduced.
In addressing audioguy's remark it may not be necessary, or even helpful, to construct a static tilted target curve in Audyssey Pro if one intends to engage the Dynamic EQ feature. Dynamic EQ will dynamically adjust the "tilt" in real-time to accommodate the actual listening levels. Any static tilt is only going to be effective at one particular listening level.