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post #391 of 394 Old 11-03-2009, 10:13 AM
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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.

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Correlation Between Subjective and Objective Measurements


In-room acoustical measurements were made at the six listening seats using a proprietary 12-channel audio measurement system developed by the Harman R&D Group. Slides 23 and 24 show the amplitude response of the different room corrections spatially averaged for the six seats (slide 23), and at the primary listening seat (slide 24). The measurements are plotted from top to bottom in descending order of preference, each vertically offset to more clearly delineate the differences. A few observations can be made:
  • 1. The six-seat spatially averaged curves (slide 23) of the room corrections do not explain listeners' room correction preferences as well as the spatially averaged curves taken at the primary seat (slide 24). This makes perfect sense since all of the listening was done in the primary listening seat.
  • 2. Looking at slide 24, the most preferred room corrections produced the smoothest, most extended amplitude responses measured at the primary listening seat. The largest measured differences among the different room corrections occur below 100 Hz and around 2 kHz where the loudspeaker had a significant hole in its sound power response. The room corrections that were able to fill in this sound power dip received higher preference and spectral balance ratings.
  • 3. A flat in-room target response is clearly not the optimal target curve for room equalization. The preferred room corrections have a target response that has a smooth downward slope with increasing frequency. This tells us that listeners prefer a certain amount of natural room gain. Removing the rom gain, makes the reproduced music sound unnatural, and too thin, according to these listeners. This also makes perfect sense since the recording was likely mixed in room where the room gain was also not removed; therefore, to remove it from the consumers' listening room would destroy spectral balance of the music as intended by the artist.

Slide 24:
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post #392 of 394 Old 11-03-2009, 01:11 PM
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Very interesting. A logarithmic 10db drop from about 20hz to 20K Hz. I'm going to try it since I think I can create that curve with Audyssey Pro.
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post #393 of 394 Old 11-03-2009, 02:34 PM
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Quote:
Originally Posted by jmichaelf View Post

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.



Slide 24:

Hi,

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.

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post #394 of 394 Old 11-03-2009, 03:13 PM
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The author started a thread on this

http://www.avsforum.com/avs-vb/showthread.php?t=1192916

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