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Stax ED-1 and ED-5 EQs emulation
Sep 18, 2013 at 7:11 AM Post #63 of 73
Sep 18, 2013 at 2:31 PM Post #65 of 73
It is theoreticly possible to use all very small microphones for recording the hrtfs.
But there are several issues to be handled. Small mics have a bad snr ratio.
I used two Sennheiser KE4-211-2 microphones. The snr is 55dB wich is good for
a small mic. It is electret and needs very(!) thin cable to fit into the ears with foam
to block the ear canal (and a battery and little circuit to energize).
I sugest for interested persons to read some papers or books about that matter
before starting. It depends on what one expects to do with the HRTFs.
Binaural simulations need very complex measurements and more complex
corrections to be simulated realisticly.
First problem is to present the needed sound incidence directions accurate enough.
That is essetial for later reproduction.
The Smyth Realizer works therefore with a headtracker and in ear mics to record
a set of HRTFs but with room information for exact reproduction of that specific
room for only this exact person. It measures also the FR of the used headphone
to invert that (or equalize the HRTFs whatever is done there). Again personalized.
Then you can feed a binaural renderer with the HRTFs and the actual orientation
(as done with the hardware box that has a binaural renderer inside). 
Static representation of the HRTFs is not very satisfying as I learned with my
properly recorded (horizontal) HRTFs. One confuses often front and back.
That can be overcome by headtracking. Nevertheless it makes the sound more
speaker like (or a bit like the Sigma but with clearer presentation).
If you want a static sim you can just record the left and right speaker seperatly and 
hold your head at exactly the same position and use that for left and right channel.
With more speakers it's clear what to do then.
 
Sep 19, 2013 at 8:23 AM Post #66 of 73
Hi Julez
Thank you for your technical comments.
 
Have you ever tried Smyth?
To see if the effect of the head tracker is really convincing.

When I listen to a binaural recording like this.
 
http://www.youtube.com/watch?v=uMkunPQMhN4
 
I find the effect striking, even so it is not registered with my head.
 
I me said at the same time it's a shame to spend 3000 euro in Smyth  whereas if the sound engineers recorded directly binaural it would cost us nothing.
 
You compare the binaural effect at the sigma.
I admit that the sigma really gives me the impression of "out of the head" except for the sounds from the rear, which is a shame for video games.
 
The sounds rear left and the sounds rear right is very well represented.
 
So I wonder if spending 3000 euros for Smyth is reasonable, just for the reproduction of sound back.
 
Sep 21, 2013 at 11:00 AM Post #67 of 73
First post edited with the correct impulses!
 
Reading your discussion about HRTF is very informative, but to make a personalized set of impulses one doesn't need a perfectly flat speaker as a source ?
 
Sigma EQ curve to come. I'll also make an impulse from the Head "subjective filter", just because I can't help myself from converting the curve to a .wav... 
biggrin.gif

 
 
900x900px-LL-41b4b699_SubjectiveFilterHAPEQ_V.jpeg
 
 
Sep 23, 2013 at 4:04 AM Post #68 of 73
Perfectly flat speakers don't exist!
But as flat as you can get is good. If you have some peaks and dips
this meens that in the dip frequency areas there is a worse snr than
at the flat parts and peaks. That's it. The FR of the speakers will be
removed by the reference measurement. So it will be perfectly flat
after treating the HRTF measurements with the reference measurement.
Remember when you divide every HRTF measurement through the
reference youll get only the difference between the measurement
with and without a person and therefore only the differences that a
head in the soundfield causes compared to a soundfield without a 
human head (and that is what you want to measure)!
 
Sep 29, 2013 at 5:17 AM Post #69 of 73
Ok I understand, that totally makes sense. I guess bass response is still a tricky part to manage, how low do you go when you measure a HRTF btw ?
 
Here is the "Subjective Filtre" impulse : http://www.petit-fichier.fr/2013/09/29/head/
Not a very spectacular EQ, but adds a bit of warmth and thickness.
 
Sep 29, 2013 at 2:23 PM Post #70 of 73
Bass doesn't matter too much when it comes to HRTFs anyway AFAIK.
 
Oct 21, 2013 at 9:52 AM Post #71 of 73
For all people interessted in HRTFs a very good basic paper:
 
https://www.dropbox.com/s/6kinjuzzocbth2w/Moeller_1992_Fundamentals-of-Binaural-Technology.pdf
 
Have fun!
 
Mar 7, 2019 at 10:36 PM Post #72 of 73
hmm going to try this, I think this thread is buried !
 
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