[JMS]

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.

 

[RRod]

 
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.

 
 
On 3) Do people have objections to using binaural mics (I assume blocked meatus) for doing personal measurements? Without calibration and in an uncontrolled environment everything will be a bit "quick and dirty", but I'm not about to put a dummy head in my listening chair b/c I try to avoid divorce…
 
On 4) Were they objecting to typical crossfeed hardware/software (e.g. bs2b) or did they have objections more generally to HRTF-based approaches?

 

[JMS]

   
 
On 3) Do people have objections to using binaural mics (I assume blocked meatus) for doing personal measurements? Without calibration and in an uncontrolled environment everything will be a bit "quick and dirty", but I'm not about to put a dummy head in my listening chair b/c I try to avoid divorce…
 
On 4) Were they objecting to typical crossfeed hardware/software (e.g. bs2b) or did they have objections more generally to HRTF-based approaches?

 
3) Not that I know, but I note that much of the recent published work (e.g. from Inner Fidelity and Harman) use simulated ear measurements. I wish there was more work being done in binaural mic measurements, which would facilitate users like us doing our own personalized correction curves.
 
4) This was the paper "Nearfield Crosstalk Increases Listener Preferences for Headphone-Reproduced Stereophonic Imagery". One explanation is that "the use of those spatial enhancement plug-ins considerably compromises other
auditory attributes such as timbral quality and perceived image width and introduces other objectionable artifacts".

 

[RRod]

   
3) Not that I know, but I note that much of the recent published work (e.g. from Inner Fidelity and Harman) use simulated ear measurements. I wish there was more work being done in binaural mic measurements, which would facilitate users like us doing our own personalized correction curves.
 
4) This was the paper "Nearfield Crosstalk Increases Listener Preferences for Headphone-Reproduced Stereophonic Imagery". One explanation is that "the use of those spatial enhancement plug-ins considerably compromises other
auditory attributes such as timbral quality and perceived image width and introduces other objectionable artifacts".

 
If I were measuring headphones for a general recommendation in a publication, I'd probably also get me a HATS. But those of us trying to be slick on our own don't really have much else to use beside binaural mics, especially if we want to try to get specific about our own HRTF. I imagine with a bit of work I could use my calibrated measurement mic to get some kind of calibration for my binaural mics, but I haven't gotten around to it yet. With VR stuff seeming to be on somewhat of a comeback, maybe we'll see some added interest—and thus better prices—for HRTF gear.
 
I haven't noticed anything objectionable with bs2b. I expect a crossfeed to decrease the stereo image, but a hard-panned sound still sounds hard-panned, just a bit more forward, and much less fatiguing. They might have been talking about some of the more complicated spatial plugins out there, though.
 
For these new cans, where exactly would this microphone array be placed? Would they attach to the frame of the HP and float between it and the ear?

 

[JMS]

   
If I were measuring headphones for a general recommendation in a publication, I'd probably also get me a HATS. But those of us trying to be slick on our own don't really have much else to use beside binaural mics, especially if we want to try to get specific about our own HRTF. I imagine with a bit of work I could use my calibrated measurement mic to get some kind of calibration for my binaural mics, but I haven't gotten around to it yet. With VR stuff seeming to be on somewhat of a comeback, maybe we'll see some added interest—and thus better prices—for HRTF gear.
 
I haven't noticed anything objectionable with bs2b. I expect a crossfeed to decrease the stereo image, but a hard-panned sound still sounds hard-panned, just a bit more forward, and much less fatiguing. They might have been talking about some of the more complicated spatial plugins out there, though.
 
For these new cans, where exactly would this microphone array be placed? Would they attach to the frame of the HP and float between it and the ear?

 
Ah yes, I should have said that the issue is not the use of an artificial head, which we do want a general mesurement to use. It's measuring between headphone and ear versus at the eardrum. If published frequency responses were measured outside the pinna, as in this paper, but using an artificial head, then it would be a reference for comparison against our own binaural head measurements. We could then equalize a headphone in-situ against the reference, giving us presumably the same functionality as the N90Q.
 
Yes the mic is attached to the HP and floated between driver and ear. The prototype shows two microphones mounted on a crossbar that runs across the HP's frame.

 

[RRod]

   
Ah yes, I should have said that the issue is not the use of an artificial head, which we do want a general mesurement to use. It's measuring between headphone and ear versus at the eardrum. If published frequency responses were measured outside the pinna, as in this paper, but using an artificial head, then it would be a reference for comparison against our own binaural head measurements. We could then equalize a headphone in-situ against the reference, giving us presumably the same functionality as the N90Q.
 
Yes the mic is attached to the HP and floated between driver and ear. The prototype shows two microphones mounted on a crossbar that runs across the HP's frame.

 
I'll have to give the paper a look at this point, otherwise you'll end up reciting the whole thing Sure would be nice of convention papers were free
 
I see the ideal world as one where we all get one free ride through a proper HRTF measurement, and out of it get a set of custom filters for applying to signals as necessary. You would then have standards for applying these filters so that you could basically plug-in to my receiver and get realistic surround sound. Since that's never going to happen (I doubt Hillary is going to make spatialization part of her platform), I do like the concept of trying to make some objective effort to personalizing the response of headphones. Still, I wonder how much better this approach will do as compared to "buy an HD800 and tone down the treble a bit with some EQ." We shall see.