[xnor]

Thanks, that clears up my confusion. Since the mic is omnidirectional it should be ok that in case a) the mic didn't point to the speakers.
 
Btw, great job.

 

[mikeaj]

Quote:

HRTFs are highly dependent on angle. The changes in the frequency response can be huge if you change the angle by a few degrees.

 
Right, I mean that these results are not hugely dependent on angle—well, positioning, at least at the positions tested.  Now that we know the chair was just shifted 1.5 feet on either side, is the magnitude of change about consistent with what's expected?  There's a difference between "can be huge" and "is huge" for the particular shifts in question I guess.

 

[xnor]

Dunno, haven't seen the non-averaged measurements. Also, I don't know how well treated the room is. There could be lots of reflections, standing waves causing nulls in the frequency response etc.
HRTFs are usually measured in anechoic chambers.

 

[JMS]

Measurements of Sennheiser HD700 (yellow), HD650 (purple), and AKG K550 (green). The HD650 differs slightly from before because I remeasured to get a more consistent result.
 
 

 
These relative measurements are consistent with the general tonality that I hear from them. The HD700 sounds like the 650 but with more, over-emphasized lower midrange and bass. However, the HD700 overall still sounds significantly better than the HD650 to me. The HD650 sounds hollow in comparison, as if there are holes in the frequency response. The K550 is too bass-light, though I would've guessed lighter than the graph shows. I suspect the K550 would be the best sounding headphones if only the frequency response line could be rotated clockwise by 10 degrees. I'll be playing with equalization curves soon to test the subjective consequences, but so far a low-shelf boost of 4db at 300hz, bandwidth=1.0 already sounds like an improvement.

 

[JMS]

[size=small]Let me add some more explanation as to what I'm trying to accomplish, which I really should have done in the initial post.[/size]
[size=small]  [/size]
[size=small] The motivation is to establish an ideal frequency response for headphones, in terms of subjective preference. For loudspeakers, we already have good research on what this response should be: when measured in-room, it's a flat line sloped downwards (see Floyd Toole's book on loudspeakers). Now, is there an equivalent statement that we can make for a headphone's frequency response?[/size]
[size=small]  [/size]
[size=small] Given the loudspeaker research, we might guess that the ideal headphone response should also be a downwards sloping line like the in-room loudspeaker response. However, we need to account for modifications to the in-room response by the listener's HRTF. To measure the listener's HRTF, we place a dummy head (mine) in the listening seat, and measure how the in-room response with the microphones mounted in-ear differs from the response with the microphones free standing. These were my measurements (a) and (b). Our candidate for the ideal headphone response would be a flat line sloped downwards but modified by this difference. This is why I said the original loudspeakers' and room's frequency response are largely irrelevant: we are only interested in the difference between two measurements.[/size]
[size=small]  [/size]
[size=small] Then we measure our headphones using the same in-ear microphones. These were my measurements (c). The ideal headphone should have a measurement (c) such that:[/size]
[size=small]  [/size]
[size=small] (c) = "flat line sloped downwards" + ((b) - (a))[/size]
[size=small]  [/size]
[size=small] Note that if the room and speakers were ideal, then (a) = "flat line sloped downwards", so we'd want (c) = (b).[/size]
[size=small]  [/size]
[size=small] Hope this clarifies the motivation behind these measurements.[/size]

 

[Puranti]

It seems kind of pointless to me as your speakers are in front of you when headphones are on the ears.
Not to mention the natural crossfeed that there is with speaker which we cannot have, us, headphones users.
In my understanding it is more important to deal with the soundtstage and crossfeed problem than a different ideal frequency response, in order to have the highest fidelity.
Am I correct ?

 

[Nevod]

Using personal HRTFs is the most correct way to crossfeed.

 

[firev1]

Quote:

It seems kind of pointless to me as your speakers are in front of you when headphones are on the ears.
Not to mention the natural crossfeed that there is with speaker which we cannot have, us, headphones users.
In my understanding it is more important to deal with the soundtstage and crossfeed problem than a different ideal frequency response, in order to have the highest fidelity.
Am I correct ?

O_o he is measuring the transfer function of his own ear to what he perceives as flat by using his calibrated speakers and measuring the FR from his ear(which will not be flat due to changes in FR due to the ear's own acoustics). By taking that HRTF, one can put on graph and correlate how the headphone would sound. As for fidelity, pursuing the ideal FR(in this case, the OP's flat response is ideal to his own ear) is paramount to fidelity. If you equalised your headphones properly, soundstaging with them can be improved. In my case, my TF10s after equalisation to approximate the ideal response sounded more open. 
 
Quote:

 

You are not bothered by the 6k peak and dip at 2-3k? Cool stuff here anyways. Consider me a fan

 

[Puranti]

Quote:

O_o he is measuring the transfer function of his own ear to what he perceives as flat by using his calibrated speakers and measuring the FR from his ear(which will not be flat due to changes in FR due to the ear's own acoustics). By taking that HRTF, one can put on graph and correlate how the headphone would sound. As for fidelity, pursuing the ideal FR(in this case, the OP's flat response is ideal to his own ear) is paramount to fidelity. If you equalised your headphones properly, soundstaging with them can be improved. In my case, my TF10s after equalisation to approximate the ideal response sounded more open.

Okay thanks for the clarification, it's always a bit tricky for me to understand when it gets technical like that.

 

[xnor]

Quote:

It seems kind of pointless to me as your speakers are in front of you when headphones are on the ears.
Not to mention the natural crossfeed that there is with speaker which we cannot have, us, headphones users.
In my understanding it is more important to deal with the soundtstage and crossfeed problem than a different ideal frequency response, in order to have the highest fidelity.

 
Quote:

Using personal HRTFs is the most correct way to crossfeed.

 
Both posts have some truth to them.
 
Besides EQing, you can add crossfeed functionality using a headphone amp with that feature or a software plugin.
You could also measure the transfer function of both ears for both speakers and use the binaural impulse response to both flatten the FR and make the soundstage more natural.
 
Imo, for headphones some sort of crossfeed is about as important as a flat FR.

 

[BlackbeardBen]

This is great work, JMS!  It falls right along the lines of what I've wanted to do for some time. 
 
There's a headphone equalization thread here, but I don't like the way it approaches equalization.  The goal stated in that thread is to get a perfectly flat perceived response - but that hardly represents the ideal or "perfect" response because of the HTRF.

 

[liamstrain]

Quote:

The goal stated in that thread is to get a perfectly flat perceived response - but that hardly represents the ideal or "perfect" response because of the HTRF.

 
Depends on what how you derive your baseline. 

 

[BlackbeardBen]

Quote:

 
Depends on what how you derive your baseline. 

 
I'm presuming that one would want to replicate such a source as that is typically how we hear real life sounds.  A perceived flat response from headphones does not replicate the perceived frequency response from a real-life near field or far field source that has a completely flat response (i.e. original, un-reproduced sounds).
 
For binaural recordings, a perceived flat headphone would likely be the ideal as the recording has already been put through a HTRF once.

 

[analogsurviver]

Subscribed the minute I saw this thread. GREAT work !

 

[Puranti]

Another question,
Wasn't it the purpose of TB Isone, to emulate a speaker sound ?