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-   -   Out-of-Head Virtualization Circuit (http://www.diyaudio.com/forums/headphone-systems/196502-out-head-virtualization-circuit.html)

oshifis 13th September 2011 12:16 PM

Out-of-Head Virtualization Circuit
 
Listening music through headphones is a necessary compromise for me. I have always been disturbed by the in-head image. I read it somewhere that it is possible to simulate the effect of the head and the ear canal, that is how the soundfield coming from the loadspeakers is modified until it reaches the ear drums. It seems quite easy: some delay from right to left channel and the way around, some freqency response modification, some frequency dependent crosstalk.
My question is: why are such (let's call it) "soundfield processors" not more common? Is it possible to realize such circuit around 2-3 opamps?
Perhaps one can plug a tiny electret microphone in the ear canal, put some test signals on the loudspeakers, and use some clever software to calculate the cross correlation function, or whatever needed to modify the audio signal of both channels..

qusp 13th September 2011 12:49 PM

crossfeed (which is the term you are looking for I think) is not so popular mainly because there have been some pretty sub-par realizations of it. the meier crossfeed amps are pretty decent, but imo it does not really suit all headphones, or all music. it takes more than a few opamps, but yes you have the idea.

there is also a more involved HRTF system (HRTF is the senses way of localizing sound and our environment with only 2 ears) called the Smyth Realizer, which you actually calibrate to your own personal HRTF senses and tracks your head movements and comes with a pretty standard stax electrostatic headphone system, but the corrections and algorithms allow for other high quality headphone systems to be used, as long as yo0u calibrate a setup file wearing those headphones

CaféNoir 13th September 2011 03:12 PM

There are plenty of software applications of crossfeed. J-river has a native plugin that works quite well.
I have tried quite a few. Problem is, after a while there seems to be a slight loss of resolution: the whole presentation is overly softened, and there is a loss of extension in bass and treble as well. Bass in particular has a tendency to become one note. Yes, it seems a bit more "natural", but going back to standard unprocessed stereo, the music is clearer and more present.

Hardware implementations are rarer. Smyth realizer is the most advanced one, and according to some french friends really worth the try. Another one which seems to lack the forementioned drawbacks of crossfeed is the SPL Phonitor. It gives you the ability to simulate precisely the virtual position of the speakers (the Phonitor was designed to be used as a studio mastering tool).

Here is some info about crossfeed and headphone psychoacoustics:
HeadWize Library - Technical Papers

Pano 13th September 2011 03:51 PM

I figured the Smyth would come up, it seems like the ultimate. I really would love to hear one. The Phonitor looks interesting for a slightly lower price. The one thing that bugs me about the Smyth is that is seem only to emulate rooms and speakers so you're stuck with what someone else has done. Is that a big limitation, or not?

Having tried, and not liked, many software and passive crossfeed and headphone enhancements, maybe the full on hardware is the way to go.

Earfanatic 13th September 2011 05:02 PM

The Meier natural crossfeed is still built in every Meier headphone amps is quite simple. It looks something like this:

http://headwize.com/images2/meier1.gif
(image is from the below mentioned page)

You can read about the principle in this page:
HeadWize - Project: A DIY Headphone-Amplifier with Natural Crossfeed by Jan Meier

qusp 14th September 2011 05:37 AM

yes apparently the Smyth is really excellent, ive heard the combination of custom in ear monitors with the smyth is to die for. i can imagine this too, because my jh13 have probably the most pinpoint accurate imaging and detail i've ever heard from any audio reproduction system, but its more in your head than outside the head, so combined with the svs it should be brilliant.

oshifis 19th September 2011 01:31 PM

Are any processed music tracks available on the net?

BTW back in the 70's I made some "dummy head" recordings with small electret capsules plugged in my ear. It was very realistic when I played them back through headphones. Sounds coming from behind me was an unbelievable experience. Everything was out-of-head, of course.

Earfanatic 19th September 2011 06:14 PM

Quote:

Originally Posted by oshifis (Post 2716177)
Are any processed music tracks available on the net?

BTW back in the 70's I made some "dummy head" recordings with small electret capsules plugged in my ear. It was very realistic when I played them back through headphones. Sounds coming from behind me was an unbelievable experience. Everything was out-of-head, of course.

You can search for binaural music... like this:
Snakecharmer Binaural by Ottmar Liebert and Luna Negra - YouTube

I heard the whole album. It is brilliant!
Somtimes visit the head-fi music recommendation topics, to find extraordinary albums.

hummel 6th October 2011 02:53 PM

I built the Meier with crossfeed some years ago and am very happy with it. I use the 'normal' crossfeed, not the bass-enhanced, and for chamber music such as string quartet it is great, bringing the soundstage forward just a bit.
My current headphone amp is the van Waarde (also described on the Headwize site) and I plan on adding crossfeed to it at some time (between the two tube stages).
Another method I have used with good results is to process the music using Canz3D (do a Google search) and an audio app such as Audacity (I use Audio Hijack on a Mac). In fact, the results with Canz3D are very good but it requires making a new copy for each piece of music. (Or you could listen in real-time from the computer I suppose.)


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