Originally Posted by satshanti /img/forum/go_quote.gif
Hello everyone!
As this is going to be my very first post in this forum, I felt I might as well make it a good one with some substance. I’m afraid it will be somewhat long, but I think it’s going to be worth it. I have collected a lot of information that can also be found elsewhere, but I felt it a good idea to present it all in one place. To make it all more bearable (and fun), I’ll use easily digestible episodes. Please bear with me and forgive my language as English is not native for me.
Part 1: Introduction
First, the Appetizer: Virtual Barbershop
If you know it, fine, if you don’t, listen to it NOW and be amazed! Now THAT is what I would call Sound Stage!
I’m going to share with you my quest for the Holy Grail of effortless, realistic, natural, life-like, transparent, and therefore “true” sound stage through headphones. I can say that I succeeded in this quest to my own full satisfaction. I’d like to share this with you all, because I’m almost sure this is a subject that every head-fier is interested in. I’m going to report my research on the valuable work already done by others, add my own theories, findings, experiments and results and present my case step-by-step, so at the end of this pseudo-scientific ranting you’ll know as much as I know and I dare to state that for many of you it could improve your listening experience. Do I sound presumptuous or downright crazy? Read on and find out.
I thought to myself: wouldn’t it be absolutely great, if I could listen to my favourite music just like the virtual barbershop. That’s what started me on my quest and although in the end I have not managed to place my favourite musicians in a virtual space as clear-cut as the barbershop, I have come very close!
A little bit of personal background first to show you my credentials. Traditional hi-fi has always been an essential part of my life, from the moment I got my first transistor radio at age 7 and gramophone at age 10. As a teenager I built my own speakers from the units in broken down TV sets and all my pocket money went into sound systems. As an adult I’ve worked as a high-end hi-fi salesman, sometimes selling equipment costing 6 figures (think Mark-Levinson, Wadia, etc.) and I was and still am a hi-fi purist, always looking for ways to keep the signal path as “clean” as possible, but only if that works and makes the sound better, not merely for its own sake. I have owned good cans in the past as well, although I rarely used them, and if I did, through the headphone output of a main or pre-amp, not through a dedicated headphone amp. Other than that, I felt, and still feel that most of the time listening through speakers is a much more realistic and relaxing experience than listening through headphones, although I must add that headphones are not to blame for that, music recordings are!
Part 2: All the World’s a Sound Stage?
I guess this chapter is not going to be news to most of you, but I’ll include it anyway to paint a complete picture and as preparation for what comes after. From the very beginning music recording has been focused on reproduction through loudspeakers rather than headphones. That’s why almost all recordings to date are “stereophonic” recordings. In modern sound studios stereo mixes are created from multiple mono tracks, but in the old days a stereo recording was made by placing two microphones a certain distance apart, and realistic playback of a 3-dimensional “stereo-image” was possible through two speakers similarly placed a certain distance apart, a phenomenon all of us know very well. This type of recording was and still is meant to be heard through a pair of loudspeakers in order to unfold and re-create its inherent 3D-image or sound stage. If heard through headphones however, each channel that’s supposed to be heard by both the left and the right ear, is in stead heard only by one ear, causing the stereo-image to collapse into a flat line between both ears.
This is the (not much of a) “sound stage” that we perceive through headphones while listening to stereophonic music recordings (99.9% of all recordings, or more) in our natural state of hearing. Note the two issues I have underlined, which I will get into separately.
Part 3: Binaural Minority Report
The Virtual Barbershop (VB) is NOT a stereophonic recording. It’s a binaural recording, tweaked digitally by way of a proprietary algorithm. The binaural recording technique is one specifically designed to be played back through headphones. The two microphones are placed in a dummy head where our eardrums are located. If the dummy would be an exact plastered copy of our own head and ears, we would have no need of digitally enhancing the recording. Anything would then sound just like the VB. I’m sure you can understand why. In order for it to create its 3D realism to such an extent in each pair of human ears, the digital algorithm that’s whispered into your ear at the end of the clip is used. It enhances the so-called head-related transfer functions (HRTF) of the recorded sounds. This is what creates the main difference between the perception of front and rear. Of the very few binaural recordings that are made, only some will give you that exact front/rear positioning like the VB, because some binaural recordings are recorded with a Jecklin Disc, or a dummy head without ears, so typically the perceived space is placed 180 degrees in the rear OR 180 degrees at the front, rather than the full 360% like the VB. It’s our ears, and in this case I mean those funny pieces of meat sticking out of the sides of our heads, that allow us to discern between a sound coming from the front or the rear. They screen the sounds coming from the rear more than they do the sounds coming from the front. The way sound is altered because of our outer ear is determined by these HRTF. So the first clue I followed was the mysterious algorithm that was whispered in my left ear. But first, as I promised above, I‘d like to share my experience with natural hearing and the lack thereof!
Part 4: The Red or the Blue Pill
I’ve noticed that when the subject comes up, almost all long-term head-fiers state that although they have tried cross-feed and even preferred its sound at the start of their head-fi “career”, after a while they more and more started to prefer listening without it. Why is that? I think it’s all between the ears!
Our brain is an amazing thing capable of performing awe-inspiring feats. As we come into the world, our ears (that is our brain) don’t have as yet the capacity to locate sounds. We have to slowly start learning to interpret those slight phase-shifts in sound, those reflections and diffractions that are caused by the unique shape of our ears and our head (HRTF). We would lose that capability if we would lose our ears or be outfitted with differently shaped ears, at least at first, but as we get used to those new ears, we would slowly gain that capability again. This shows that we are able the “re-program” our brain in order to preserve our capacity for 3-dimensional hearing. In case of the new set of ears we merely have to continue our inherent capability for “natural” hearing, based on those subtle HRTF cues, so although the transitional adaption period might be slightly confusing and tiring for our brain, once re-programmed, we are again able to listen effortlessly to the sounds in the world around us. Now, what does this have to with anything?
Let’s talk about headphone fatigue. This is the reason why I said that I personally always preferred listening to speakers rather than headphones. While we listen to stereophonically recorded music through headphones our brain is receiving auditory information that is in some way distorted and unnatural. Some aspects of it like the frequency spectrum and the timing are OK, but the directional cues are plainly NOT there in the way our brain is used to receiving them. So rather than give up and leave us to the narrow between-the-ears stereo-image we actually perceive in that natural state, our brain starts the process of re-programming itself in order to re-instate the illusion of natural positional hearing. This takes time and effort. It does cause fatigue, but after some time our wonderful brain IS actually able to have us believe that we are listening to a speaker-like sound stage. And the more we get used to it, the less fatiguing it gets and we are happy. This is the situation almost all of you find yourselves in. It’s not exactly natural, and it still does take some small effort to the brain to maintain the illusion, but it kind of works, and at least there are absolutely no changes made to the frequency spectrum, the timing or resonant harmonics of the source.
This has been the one and only choice available, but now I’m going to offer you a pill of a different colour. I’m not claiming it’s the better choice. It’s the one I chose and I’m absolutely happy with it. What if we could spare the brain the initial time and effort to re-program itself for headphone listening and the continuous effort it takes to uphold an illusion. I believe that it still creates fatigue in the most experienced of head-fiers, because it takes so much more effort to translate those invalid auditory cues into a coherent sound stage, at least compared to the natural HRTF phase-based cues. As most of you know, I’m not the first one to get the idea of some sort of pre-processing to make the sound more natural. The thread title does mention cross-feed, so that’s one of the things I started experimenting with.
Part 5: Cross-Feed, just a newbee toy?
Up until a year ago I hadn’t owned a set of cans for about 15 years, for the reasons mentioned above. There were three reasons why I gave headphones another chance. First, because my family situation didn’t allow me to listen to music through my speakers at the proper sound level anymore. Second, because I stumbled upon this forum and started reading all kinds of amazing stuff about headphones and relatively cheap dedicated head amps. And third, the cross-feed circuits built into them, because at that time that seemed like the solution to the problem I had with headphone listening. I bought myself a Grado SR-60 and a Headstage Lyrix amp, connected it to my CD player, and... I was enchanted!
Little did I know how many more revelations were yet to come. I’ll make a long story short at this point because my subsequent attack of upgraditis is not relevant to the subject at hand. I used the cross-feed setting on the Lyrix almost all the time although I started noticing that the perceptual difference between with and without was getting smaller AND I did notice that without it the sound was more accurate as far as frequency and timing was concerned and more transparent. While making the change from using my CD player as a source to my computer, I upgraded to a Derek Shek NOS DAC, a DIY-built OTL tube amp (NOS-rolled) and headphones alternating between an AKG K340 and K240 Sextett. All in all a set-up I am absolutely happy with at the moment. I play mostly lossless files through Foobar with bit-perfect output obviously.
As I had left the cross-feed of the Lyrix behind, I listened without it through my new system for a few weeks and although I did indeed learn to experience a certain measure of depth in the music, as before, it was way too little and too unnatural for my taste and in some recordings I didn’t like it at all. So I started looking for an alternative to the hardware cross-feed circuit I had experienced already and found out that there were actually a few Foobar plugins offering software cross-feed. The head-fi sticky thread only mentions 4Front and naive software, but these fall way short in terms of realism. Browsing the forum I stumbled upon Boris Mikhaylov’s Bauer stereophonic-to-binaural DSP (BS2B). The name was already very promising and having played around with it and its settings, I liked it quite a bit. It emulates various hardware based cross-feed circuits and makes subtle changes to the sound. In a way it offers an option in-between the two extremes mentioned above. It helps the brain a little bit more with deciphering spatial cues and building a small-scale sound stage, but still leaves something for the brain to do: expanding the soundstage outward; all in all, a good compromise, and definitely an option.
At this point in time I found the virtual barbershop demo, clearly demonstrating that even more might be possible, so I started digging deeper.
Part 6: Professional Positional Audio
I’ll continue where I left off at the end of part 3 with my report on the search for that mysterious Cetera algorithm responsible for the WOW-factor in the VB. I found that the demo was created by a manufacturer of hearing aids called Starkey. The Cetera algorithm was the “software” part of a hearing aid developed in the late nineties, in cooperation with another company called QSound Labs. This company, then as well as now, specializes in a wide spectrum of 3D audio solutions. Their technology is implemented in various ways, software as well as hardware based. In fact, I discovered that since the nineties various companies had started research into 3D audio, both for studio purposes, like music recording and movie surround tracks, as well as positional audio for the PC (think first-person shooters). SRS Labs, for instance, has worked in the same field as QSound. Both these companies have developed software packages for the PC, able to process and enhance sound and music in a variety of ways, including headphone surround. I’ll not go into details here, as their products usually are shipped with certain hardware, like PC sounds cards, or if sold separately, are only useable as part of the operating system, upsampling, downsampling, etc, so doesn’t really serve the purpose of audiophile music listening.
There’s one company however that I didn’t as yet mention, Lake Technology. This Australian company developed digital audio algorithms for recording studios. One of their algorithms allowed movie studio technicians to use headphones to work with and monitor 5.1 AC3 tracks. After Dolby Laboratories licensed the technology and then even bought the whole company, it became known as Dolby Headphone. Being a company with a slightly different focus, compared to the others mentioned before, Dolby Headphone was licensed to manufacturers of DVD-players and other home-theatre equipment, where its algorithms were hardwired so-to-speak into the signal path.
Now, all these technologies were a long way from being easily useable for my purpose, to create a high-quality, PC-based 3D sound through headphones. The technology exists, but we audiophile headphone listeners don’t present a large market to begin with and is not exactly an obvious market for such companies, especially considering that most of you are convinced purists like myself, for whom any kind of sound-processing represents evil. So why would any of these companies bother to create something like a Foobar plugin, when they can make money licensing their technology to manufacturers of products that are bought in huge quantities or to professional recording studios.
That’s another taboo we audiophiles tend to suffer from. Most of recorded music is processed and down-mixed by exactly these kinds of technologies, and we are ready to defend our purist ways by preserving the “original” sound, when that sound is not original to begin with. So what would be wrong with using those technologies to merely extrapolate the sound engineer’s purpose and change a stereophonic track into a binaural one, suitable for headphone listening?
Investigating Dolby Headphone I stumbled upon THIS thread at the Hydrogenaudio forum and discovered that someone had had similar thoughts already and that turned out to be the singular most significant discovery I made during my research.
Part 7: Chungalin’s Dolby Headphone Wrapper
This guy (or girl, I’m not sure, you never know, in the guise of Calimero, goes by the name of Chungalin in various forums, head-fi included) already developed a great piece of software around 3 years ago, called the Dolby Headphone Wrapper (DHW). It’s an official 3rd party Foobar plugin (foo_dsp_dolbyhp) and using it correctly and in combination with certain other plugins improves regular cross-feed processing by several orders of magnitude (imho). Reading the thread I mention above gives one a good idea of the various developments and improvements that have been made in connection with the wrapper. I won’t repeat everything that’s said there, but in case you don’t feel like reading that whole thread I’ll summarize it for you.
The Dolby Headphone algorithm is not only built into stand-alone dvd-players, but is also part of a number of commercial software dvd-players for the pc. One little file in particular takes care of it: dolbyhph.dll and Chungalin wrote a Foobar plugin that utilizes that file. There are demo-versions of software dvd-players available for download that include that dll-file. So the wrapper converts a 5.1 channel input into a 2 channel output for headphones. Now, the big question and challenge mainly featuring in the Hydrogen thread is: What can we put before DHW to change a 2 channel stereo track into a 5.1 surround track? Hancoque’s large post in the thread is an excellent resume of the process of finding answers to that question.
Until now not much of what I’ve shared with you has been my own unique effort. I’ve just gathered relevant information in one place, merely adding some conclusions and opinions. Now I’d like to share with you my review of the different methods of how to use DHW and the results of my own experimenting and tweaking. These days, except for the one binaural album in my possession and the VB, all the rest of my music, be it rock, classic, pop or folk, I listen to through my customized DSP chain, based on Dolby Headphone. The slight alterations in the frequency spectrum and resonant harmonics are negligible in my perception, so with most music I don’t feel I lose anything. But the gains are immense. I have something better than a speaker-like soundstage. I have a live soundstage. Words cannot begin to describe what these DSP’s do to any source of music, no matter how it’s recorded.
So what is the missing link? The last chapter will be my actual contribution. I’m going to tell you step-by-step what I’ve done and the results of my testing.
Part 8: The Icing on the Cake
The options that Hancoque presented and shared in his foo_dsp_upmix are the final developments of the “straightforward” approach to the upmixing issue. It basically takes the two stereo channels and sort of spreads them around the 6 channels. Of the dsp’s he created, I personally found the double center option slightly better than the full front option and a lot better than the full rear option. I could have happily lived with his upmix dsp’s combined with the DHW, as the results are already absolutely great, but … I did happen to have some experience with home-recording software like Cubase and Cakewalk and their use of so-called VST plugins. I was aware of the amazing pieces of software that are available for changing the number of channels in a multi-track recording, so I was wondering if there wouldn’t be a more intelligent way to spread the stereo signal around the available 6 channels, and of course there is!
A guy named Steve Thomson created a free piece of software called V.I. Stereo to 5.1 Converter VST Plugin Suite (VI) that incorporates a number of algorithms (i.e. ambisonics) to place sounds into the proper place in the 3-dimensional sound stage. It creates a living, breathing atmosphere out of the slightest auditory cues available in the original signal. No matter how the recording is made, as long as it’s stereophonic and not binaural, VI will create a 360 degrees image that is absolutely believable, and, miraculously, hardly takes anything away from or adds anything to the frequency spectrum. In my perception it is VI that is actually responsible for placing echoes, resonances and other subtle or not so subtle cues at the proper place in the virtual sound stage, without ever overdoing it in such a way that it’s perceived as unnatural. A singer for instance is typically placed front center, but the acoustic reverberation of the voice that is part of the original recording is placed all around the listener just as it should be if the singer would be standing before you in a real room. And this applies to all instruments and sounds. The result is mind-blowing, and you’ll have to hear it to believe it. Of course some recordings work better than others with it, but all in all it’s pretty amazing how intelligently VI and Dolby Headphone work together to create such a realistic sound space. I have spent considerable time finding the perfect setting for VI where the focus and front/rear division is optimal and most realistic. I suggest you start with this and only if you are the experimenting type, change the settings and see if your taste is different than mine.
So, what do you need? I’ve already explained above how to get the DHW. Place this last in the DSP chain (well, not much of a chain as there are only two DSP’s needed). Configure it by pointing it to the dolbyhph.dll on your PC, set the room to the DH1 reference room (the other rooms are too large), set amplification at 100% (changing this slightly affects sounds quality similar to the use of ReplayGain) and make sure to leave Dynamic Compression off. Now download the VI Suite (Google it) and the old VST host foobar plugin (foo_dsp_vst), so NOT George Yohng’s VST wrapper as this plugin doesn’t support multiple channels. Place the VST host (bridge) first in the chain above the DHW and point it to the VI.dll file that came with the VI Suite. Now press “Show Editor” and you’ll be able to adjust the VI settings, even while music is playing. I strongly recommend you use the following settings:
Of the three lights on the right side of the panel the first (on/off) should obviously be on, movie mode should be off and LFE on. Of the 4 main sliders the two middle ones should be left where they are, in the middle at the default setting. I call this position 0. The rest of the settings range from -5 to 5. The two remaining sliders (top and bottom) should be slightly left of the -4 position in such a way that the top slider just covers the little white marker, and the bottom slider just barely shows the marker. Sliding these only a tiny bit to the left or right already creates a major shift in sound, so make sure they are placed like this:
Attachment 7875
UPDATE: Go to the end of page 4 for revised and more transparent settings!
There are a few things that might spoil it for you. I guess these DSP’s take up quite a bit of processing power, so I’m not sure which computer will be up to the task and which not. I use a Core Duo. The old VST bridge unfortunately is not a very stable program. It tends to crash. In my case it always displays an error message AFTER I have stopped listening and close Foobar, so not much of a problem, but I DID have problems playing FLAC’s. I have now converted all my music to TAK, an alternative lossless format, which works just fine, MP3’s and OGG’s as well. Certain loud pieces of music might clip after it has passed through the chain. Only in that case I would either use ReplayGain or set the amplification of DHW a bit lower (at 70%), because to my ears at least, there is a barely noticeable loss in sound quality lowering the volume of the music digitally, not a lot, but enough.
Well, that’s it. Thanks for your patience. I hope it has been worth it.
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