JMS
100+ Head-Fier
- Joined
- Sep 16, 2002
- Posts
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An intruiguing paper was published in May 2015 that apparently discusses the science behind AKG's latest $1500 flagship and possibly the latest JBL Everest headphones. I'm surprised that there's been absolutely no press for the paper and not much more for the headphone (get on this Tyll!).
Here are the key points:
- For some headphones, it is possible to accurately measure its perceived frequency response using a microphone array between the headphone transducers and pinna. This means a headphone can measure its own output in-situ, on a user's head, without having to place a microphone at the user's eardrum!
- Certain design considerations help ensure accurate measurements using the microphone array: transducer firing a uniform wavefront directly into the ear, and cavity formed by the ear cushion not introducing artifacts. These considerations are incorporated into the illustrated "AKG prototype" whose profile looks just like the N90Q.
- Their intended target response curve is based on the "Harman curve" published in 2013 by Olive et al. I note that in reviewed.com's N90Q review there's mention of an "equal loudness contour" but not of the Harman cruve. They also discuss a crossfeed based on HRTF's.
My comments:
1) While the measurement is shown to correlate well with equal loudness perception, it does not guarantee, apriori, correlation with subjective preference. After all, narrow band tone bursts were chosen to reduce effects from psychoacoustic adaptation. It's still possible that what applies in determining loudness of tone bursts may not transfer to subjective enjoyment of music.
2) I don't think the Harman curve is directly applicable since that is referenced off flat measured in-room response, and this paper's equal loudness curve is derived with respect to flat loudspeakers playing "in close proximity to the subject", with no specifications of measured in-room response. Not certain that I'm understanding this paper's setup correctly.
3) This provides some validity to measuring personal headphone response using in-ear microphones, as I had once reported results on in this forum.
4) Ironically, in the same conference a paper was published saying that all existing crossfeeds are subjectively neutral or harmful, while proposing a new nearfield-based approach that's actually beneficial.
Here are the key points:
- For some headphones, it is possible to accurately measure its perceived frequency response using a microphone array between the headphone transducers and pinna. This means a headphone can measure its own output in-situ, on a user's head, without having to place a microphone at the user's eardrum!
- Certain design considerations help ensure accurate measurements using the microphone array: transducer firing a uniform wavefront directly into the ear, and cavity formed by the ear cushion not introducing artifacts. These considerations are incorporated into the illustrated "AKG prototype" whose profile looks just like the N90Q.
- Their intended target response curve is based on the "Harman curve" published in 2013 by Olive et al. I note that in reviewed.com's N90Q review there's mention of an "equal loudness contour" but not of the Harman cruve. They also discuss a crossfeed based on HRTF's.
My comments:
1) While the measurement is shown to correlate well with equal loudness perception, it does not guarantee, apriori, correlation with subjective preference. After all, narrow band tone bursts were chosen to reduce effects from psychoacoustic adaptation. It's still possible that what applies in determining loudness of tone bursts may not transfer to subjective enjoyment of music.
2) I don't think the Harman curve is directly applicable since that is referenced off flat measured in-room response, and this paper's equal loudness curve is derived with respect to flat loudspeakers playing "in close proximity to the subject", with no specifications of measured in-room response. Not certain that I'm understanding this paper's setup correctly.
3) This provides some validity to measuring personal headphone response using in-ear microphones, as I had once reported results on in this forum.
4) Ironically, in the same conference a paper was published saying that all existing crossfeeds are subjectively neutral or harmful, while proposing a new nearfield-based approach that's actually beneficial.