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AES 2012 paper: "Relationship between Perception and Measurement of Headphone Sound Quality" - Page 5

post #61 of 130

Really interesting study. Thanks!

post #62 of 130
Quote:
Originally Posted by xnor View Post

I'm wondering how you came up with the "perceived spectral balance" in slide 25.

 

For example HP4 clearly shows boosted bass and treble, but the perceived spectral balance looks like HP2.

Perceived spectral balance is based on the average spectral rating given by the listeners in each trial.  For each headphone, the listeners give a rating from -5 to +5 in 7 equal log spaced frequency bands where -5 is too little energy, 0 is ideal, and +5 is too much emphasis. If they draw a flat line that means the headphone as an "ideal" or neutral spectral balance.

 

As I pointed out in the blog (and the paper), HP4 had a leakage issue with certain listeners  (e.g. Listener 1) due to poor fit/coupling to their heads, so they received and perceived less bass than other listeners. As a result this brought down the perceived spectral balance rating of HP4 below 200 Hz. We confirmed this by measuring the frequency response of HP4 on the listeners with in-ear microphones.

 

Bass leakage is a real nuisance variable with subjective and acoustical measurements of headphones. You can see in the slides that some manufacturers have done a better job  than others at minimizing bass leakage across listeners by putting in a controlled air leak and/or making the headphones so they fit most listeners.


Edited by Tonmeister2008 - 4/23/13 at 4:02pm
post #63 of 130

I see, thank you.

post #64 of 130
Quote:
Originally Posted by mikeaj View Post

Guessing game?

 

1 - Audeze LCD-2  (flat subbass extension, treble extension)

2 - AKG K701   (bass rolloff at 100 Hz, upward slope)

3 - AKG K550   (elevated bass but otherwise somewhat diffuse-field, 9 kHz spike)

4 - Bose QC15  (like 3, but not 9 kHz spike)

5 - Beats Studio  (hole in midrange, sharp rolloff under 40 Hz)

6 - V-Moda Crossfade  (hole in midrange, subbass issues, treble extension issues)

 

Wait, that's just the order they're listed, except I swapped 4 and 5.  Beats Studio should be the one that rolls off sharply under 40 Hz.

 

mikeaj,

 

I concluded the same as you :)

 

Graphs 2 and 3 look like Grado's, to me. I cannot tolerate hot treble. I prefer modding for flat FR with just a tiny bit of U shape in the bass and treble.

 

Good article.

post #65 of 130

I think Grados would measure quite a bit worse with the same ear simulator.

 

More questions to Mr. Olive regarding the measurements (GRAS 43AC with KB1060 pinna):

 

KB1060 is a small pinna described as:

Quote:
  •  Small ears are typical of American and Euro-  
  pean females as well as Far-eastern males and  
  females

Why not choose the large one:

Quote:
  •  Large ears have pinna sizes typical of American  
  and European males

 

And how was this whole construction calibrated?

post #66 of 130
Quote:
Originally Posted by xnor View Post

I think Grados would measure quite a bit worse with the same ear simulator.

 

More questions to Mr. Olive regarding the measurements (GRAS 43AC with KB1060 pinna):

 

KB1060 is a small pinna described as:

Why not choose the large one:

 

And how was this whole construction calibrated?

We now have both large (male) and small (female) pinnae. The smaller ones give a better fit-seal for intra- concha type phones, but we are using the large ones now for circumaural type phones.

 

We are all equal opportunity research lab when it comes to dummies and pinnae (although we've not purchased the war veteran pinnae)

 

Not sure what you mean by calibration. The GRAS couplers/mics are sold as calibrated devices and you can send them out for yearly calibration. You can also  calibrate the SPL of the  microphones with a piston phone.

post #67 of 130

That's good. So I assume the L/R measurements on slide 25 are raw, in other words not equalized.

 

What I always wondered is why headphone measurements don't use an equalization based on calibrated (flat) speakers at +/- 30° instead of free or diffuse field.

post #68 of 130
Quote:
Originally Posted by xnor View Post

That's good. So I assume the L/R measurements on slide 25 are raw, in other words not equalized.

 

What I always wondered is why headphone measurements don't use an equalization based on calibrated (flat) speakers at +/- 30° instead of free or diffuse field.

 

Indeed! I also find interesting that, for full size headphones at least, using an approach as described here yields similar results relative to when headphones are measured using an "anechoic" plate. Both approaches might have some slight differences, but correlate highly with what I personally perceive.


Edited by ultrabike - 4/24/13 at 4:50pm
post #69 of 130
Quote:
Originally Posted by xnor View Post

That's good. So I assume the L/R measurements on slide 25 are raw, in other words not equalized.

 

What I always wondered is why headphone measurements don't use an equalization based on calibrated (flat) speakers at +/- 30° instead of free or diffuse field.

The measurements are based on an average of 5-6 re-seatings. They aren't equalized in the sense that we haven't tried to remove the transfer function of the GRAS 43AG , which has nothing to do with free or diffuse field equalization.

 

What you are talking about is what the ideal target response curve should be for a headphone: diffuse field, free-field, something in between? There are many different thoughts on that but we are presenting a paper on this topic at the upcoming Rome AES where we tested several options.

 

P10-3 Listener Preferences for Different Headphone Target Response CurvesSean Olive, Harman International - Northridge, CA, USA; Todd Welti, Harman International - Northridge, CA, USA; Elisabeth McMullin, Harman International - Northridge, CA USA
There is little consensus among headphone manufacturers on the preferred headphone target frequency response required to produce optimal sound quality for reproduction of stereo recordings. To explore this topic further we conducted two double-blind listening tests in which trained listeners rated their preferences for eight different headphone target frequency responses reproduced using two different models of headphones. The target curves included the diffuse-field and free-field curves in ISO 11904-2, a modified diffuse-field target recommended by Lorho, the unequalized headphone, and a new target response based on acoustical measurements of a calibrated loudspeaker system in a listening room. For both headphones the new target based on an in-room loudspeaker response was the most preferred target response curve. 
Convention Paper 8867

post #70 of 130
Quote:
Originally Posted by Tonmeister2008 View Post

The measurements are based on an average of 5-6 re-seatings. They aren't equalized in the sense that we haven't tried to remove the transfer function of the GRAS 43AG , which has nothing to do with free or diffuse field equalization.

 

What you are talking about is what the ideal target response curve should be for a headphone: diffuse field, free-field, something in between? There are many different thoughts on that but we are presenting a paper on this topic at the upcoming Rome AES where we tested several options.

 

P10-3 Listener Preferences for Different Headphone Target Response CurvesSean Olive, Harman International - Northridge, CA, USA; Todd Welti, Harman International - Northridge, CA, USA; Elisabeth McMullin, Harman International - Northridge, CA USA
There is little consensus among headphone manufacturers on the preferred headphone target frequency response required to produce optimal sound quality for reproduction of stereo recordings. To explore this topic further we conducted two double-blind listening tests in which trained listeners rated their preferences for eight different headphone target frequency responses reproduced using two different models of headphones. The target curves included the diffuse-field and free-field curves in ISO 11904-2, a modified diffuse-field target recommended by Lorho, the unequalized headphone, and a new target response based on acoustical measurements of a calibrated loudspeaker system in a listening room. For both headphones the new target based on an in-room loudspeaker response was the most preferred target response curve
Convention Paper 8867

 

Interesting stuff!

post #71 of 130
Quote:
Originally Posted by Tonmeister2008 View Post

The measurements are based on an average of 5-6 re-seatings. They aren't equalized in the sense that we haven't tried to remove the transfer function of the GRAS 43AG , which has nothing to do with free or diffuse field equalization.

 

What you are talking about is what the ideal target response curve should be for a headphone: diffuse field, free-field, something in between? There are many different thoughts on that but we are presenting a paper on this topic at the upcoming Rome AES where we tested several options.

 

P10-3 Listener Preferences for Different Headphone Target Response CurvesSean Olive, Harman International - Northridge, CA, USA; Todd Welti, Harman International - Northridge, CA, USA; Elisabeth McMullin, Harman International - Northridge, CA USA
There is little consensus among headphone manufacturers on the preferred headphone target frequency response required to produce optimal sound quality for reproduction of stereo recordings. To explore this topic further we conducted two double-blind listening tests in which trained listeners rated their preferences for eight different headphone target frequency responses reproduced using two different models of headphones. The target curves included the diffuse-field and free-field curves in ISO 11904-2, a modified diffuse-field target recommended by Lorho, the unequalized headphone, and a new target response based on acoustical measurements of a calibrated loudspeaker system in a listening room. For both headphones the new target based on an in-room loudspeaker response was the most preferred target response curve. 
Convention Paper 8867


Interesting indeed. I didn't know there's any brand out there who implements such curve for its product. Looking forward to reading your paper.

post #72 of 130
Quote:
a new target response based on acoustical measurements of a calibrated loudspeaker system in a listening room. For both headphones the new target based on an in-room loudspeaker response was the most preferred target response curve

This is exactly what I was asking for and similar to how I equalize headphones by switching back and forth between calibrated speakers and headphones.

post #73 of 130

I'm confused - does the Harmon paper indicate, then, that headphone users are seeking a flat frequency response?

post #74 of 130
Quote:
Originally Posted by MrMateoHead View Post

I'm confused - does the Harmon paper indicate, then, that headphone users are seeking a flat frequency response?

Read the blog post linked on the previous page:

Quote:
The results provide evidence that trained listeners preferred the headphones perceived to have the most neutral, spectral balance.

 

The correct order appears to be:

HP1: LCD2r2
HP2: K701
HP3: Bose QC15
HP4: K550
HP5: Beats Studio
HP6: Crossfade

 

Taking the perceived spectral balance plots into account some listeners had problems getting proper seal with the AKG cans. This would also explain how some reviewers say their K701 has enough bass ("bass-heavy" version*) and others say it is lacking bass.

*) The old "explanation" was that there are huge manufacturing variations leading to bass-heavy and light versions..


Edited by xnor - 4/25/13 at 11:34am
post #75 of 130
Quote:
Originally Posted by xnor View Post

Read the blog post linked on the previous page:

 

The correct order appears to be:

HP1: LCD2r2
HP2: K701
HP3: Bose QC15
HP4: K550
HP5: Beats Studio
HP6: Crossfade

 

Taking the perceived spectral balance plots into account some listeners had problems getting proper seal with the AKG cans. This would also explain how some reviewers say their K701 has enough bass ("bass-heavy" version*) and others say it is lacking bass.

*) The old "explanation" was that there are huge manufacturing variations leading to bass-heavy and light versions..


Thanks for the clarification.

 

Is it just me or does it seem that most testers had a tendency to judge the phones more on Bass than other factors? Deviation from perceived 'flat response' seems to have been less bad in headphones with elevated treble. Recession in the mid-range seemed to ensure a 'bass heavy' presentation.

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