I'm building a 2>3 channel stereo matrix "extractor" (no active steering) with some BW limit options based on reading David Griesinger (formerly of Lexicon) papers, largely because I now have a 42 inch HD TV in the middle. I've also included the option of a holographic generator (inter-aural cancellation) circuit, with and without BW limiting for the L&R outputs.
I read somewhere that if you delay the L&R outputs relative to the center output, you double the amount of perceived separation between the center and the L&R signals. I think the recommendation for delay was about 1-10mS, but I'm not sure if that would cause an objectionable comb filter effect since the matrix is effectively passive and therefore has some crosstalk. I plan to research this when I get the basic extractor circuit done. I think the delay takes advantage of precedence effect, and may effectively cause some decorrelation. This may increase the 3-D effect of a singer in the middle.
I read somewhere that if you delay the L&R outputs relative to the center output, you double the amount of perceived separation between the center and the L&R signals. I think the recommendation for delay was about 1-10mS, but I'm not sure if that would cause an objectionable comb filter effect since the matrix is effectively passive and therefore has some crosstalk. I plan to research this when I get the basic extractor circuit done. I think the delay takes advantage of precedence effect, and may effectively cause some decorrelation. This may increase the 3-D effect of a singer in the middle.
Bob, if you can (temporarily) run vst plugins check out the Voxengo free plugins. They have a plugin that can delay the mid/side separately. I've played with it a long time ago to see what that sounds like. It can delay in cycles or milliseconds. I was able to get weird sounds out of it (lol).
Here's a link: http://www.voxengo.com/product/sounddelay/
Here's a link: http://www.voxengo.com/product/sounddelay/
Voxengo Sound Delay said:
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Thanks, but I'm still an all analog guy. The computer is in the other room so no VST options in my main system.
I can't say I've looked at GD plots in a joint measurement of ambience and mains.
I usually look at the 2 separately, as I can isolate them.
The only data I collect needing the both of them together is to determine or check the delay set for the ambient channels. So I don't have that many measurements with the both of them.
For the group delay I'm still looking at both REW and APL_TDA. It made it easier to see the ambience channel's time spread too. I should redo some of the measurements sometime soon, but I'm kinda busy with other things at the moment and am enjoying the sound I've got in the mean time.
I usually look at the 2 separately, as I can isolate them.
The only data I collect needing the both of them together is to determine or check the delay set for the ambient channels. So I don't have that many measurements with the both of them.
For the group delay I'm still looking at both REW and APL_TDA. It made it easier to see the ambience channel's time spread too. I should redo some of the measurements sometime soon, but I'm kinda busy with other things at the moment and am enjoying the sound I've got in the mean time.
Interesting stuff wesayso and Jim. This is some next level "stereo" reproduction... from room correction (really room reduction) to room enhancement! As a recording engineer, I have some issues with the concept from a purist reproduction perspective - 5.1 in fairly dead rooms is a more reliable format for delivering the "in-studio" experience "in-home". This seems just like a kind of polyfill or stopgap for surround music.
Not that any of that means I think you should stop doing it, or that it isn't making the listening experience better in your rooms. It's just a troubling concept to me... well, I guess it is just a room-specific stereo->surround upmixing technique. It certainly exceeds the scope of stereo reproduction and points to the limitations of the stereo format.
(I'm browsing your thread on GS now Jim.. hopefully that will shed some light on your design philosophies!)
Agree. 1 and 2 are solved by looking at a CSD plot, right? 3 through 5 require multiple microphones. Trinnov uses the dodecahedron setup for analysis of these factors (processed ambisonic style I assume). Too much information for a static 2D image, that's for sure.
Not that any of that means I think you should stop doing it, or that it isn't making the listening experience better in your rooms. It's just a troubling concept to me... well, I guess it is just a room-specific stereo->surround upmixing technique. It certainly exceeds the scope of stereo reproduction and points to the limitations of the stereo format.
(I'm browsing your thread on GS now Jim.. hopefully that will shed some light on your design philosophies!)
Agree. 1 and 2 are solved by looking at a CSD plot, right? 3 through 5 require multiple microphones. Trinnov uses the dodecahedron setup for analysis of these factors (processed ambisonic style I assume). Too much information for a static 2D image, that's for sure.
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I think your reading an intent into what I (we?) are doing that is a bit off the mark. For myself, I am exploring a fully encompassing 2 channel listening experience, not a altered or quasi surround enhancement. To me, the full 2 ch listening experience includes the proper listening environment. That environment includes the dynamic/acoustic qualities of the listening room. Like most people, the room I listen in isnt optimal. So what wesayso and I are discussing mostly is how to adapt an imperfect room to come closer to an ideal one utilizing additional sources, DSP, and room treatment.
What is lacking in small rooms the most is a adequate sense of proper ambience. While wesayso and I are going about it in different ways, I think we are trying to reach the same goal.
I can understand you being troubled. Much of the ground here doesn't not have well established guidelines. Certainly, there is a lot of experimentation going on. But when you say it exceeds the scope of stereo reproduction, I think we would have to define what the model for that is to begin with.
From a listeners point of view, that is usually a modest system in a small untreated room. While this maybe the dominate experience, I dont think its the ideal one.
As said above, the scope of 2 ch reproduction must include the environment its being reproduced in.
Thanks for the clarification Jim.
I agree that the goals of stereo reproduction are rather loosely defined. Some recordings are exceedingly dry and rely exclusively on listening room acoustics to generate ambience. Other recordings include extensive ambience which may work against natural room acoustics - or your chosen DSP acoustic. Some are optimized for headphone reproduction (a fringe area, but still - don't get me started on the moving target that is headphones!)
Certainly, the acoustics of the typical domestic listening room are not preferable for creating this ambience or spatial impression from a 2 channel source. So I understand why and what it is that you are doing (using additional channels to create a 'better listening room' spatial impression). Yet, I fail to see how it differs functionally or even philosophically from upmixing stereo to 5.1. In the latter case, one is adding ambience - artificial listening room ambience in your case (not necessarily "recovering ambience") - and reproducing this upmix on a standard 5.1 setup. The only difference is that the placement of the speakers is not standardized in your setups.
In your solution to the ambience problems of 2 channel reproduction in small rooms, the ambience, although artificial, cannot be chosen by the artist and tailored to the content. In "pure 2 channel" stereo, this is an unavoidable limitation. But since you are already dabbling in surround sound upmixing (even if only to the end of enhancing stereo listening room acoustics), it may be worthwhile to consider the well thought out, standardized formats for surround sound, which was also designed to solve these same problems (among other things). If you were using a standard 5.1 setup - even with your own custom stereo upmix as you are using now - you would at least allow for the playback of content designed for this situation: discrete reproduction channels for artificial ambience.
I understand and agree that 2 channel music greatly benefits from ambience in the listening environment. Yet, this "playback ambience" is not defined, and cannot be defined, within the constraints of the stereo format. "Treated small room" 5.1 basically solves these problems (listening room does not create desirable ambience, artist has control over ambience reproduced in playback environment).
All that said, I think it is quite interesting stuff that you are doing, coming from an understanding of the shortcomings of stereo reproduction in small rooms, and surely is giving me food for thought...
I agree that the goals of stereo reproduction are rather loosely defined. Some recordings are exceedingly dry and rely exclusively on listening room acoustics to generate ambience. Other recordings include extensive ambience which may work against natural room acoustics - or your chosen DSP acoustic. Some are optimized for headphone reproduction (a fringe area, but still - don't get me started on the moving target that is headphones!)
Certainly, the acoustics of the typical domestic listening room are not preferable for creating this ambience or spatial impression from a 2 channel source. So I understand why and what it is that you are doing (using additional channels to create a 'better listening room' spatial impression). Yet, I fail to see how it differs functionally or even philosophically from upmixing stereo to 5.1. In the latter case, one is adding ambience - artificial listening room ambience in your case (not necessarily "recovering ambience") - and reproducing this upmix on a standard 5.1 setup. The only difference is that the placement of the speakers is not standardized in your setups.
In your solution to the ambience problems of 2 channel reproduction in small rooms, the ambience, although artificial, cannot be chosen by the artist and tailored to the content. In "pure 2 channel" stereo, this is an unavoidable limitation. But since you are already dabbling in surround sound upmixing (even if only to the end of enhancing stereo listening room acoustics), it may be worthwhile to consider the well thought out, standardized formats for surround sound, which was also designed to solve these same problems (among other things). If you were using a standard 5.1 setup - even with your own custom stereo upmix as you are using now - you would at least allow for the playback of content designed for this situation: discrete reproduction channels for artificial ambience.
I understand and agree that 2 channel music greatly benefits from ambience in the listening environment. Yet, this "playback ambience" is not defined, and cannot be defined, within the constraints of the stereo format. "Treated small room" 5.1 basically solves these problems (listening room does not create desirable ambience, artist has control over ambience reproduced in playback environment).
All that said, I think it is quite interesting stuff that you are doing, coming from an understanding of the shortcomings of stereo reproduction in small rooms, and surely is giving me food for thought...
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As Jim said, our methods are wildly different but we are trying to reach a common goal. I completely understand that this is deviating from a purist point of view.
But I do believe there are differences between what we are doing and a multichannel upmix. The both of us are trying to compensate for our listening environment, making the room behave more like an ideal listening environment. I am extremely handicapped compared to Jim as I am using a living room. But by eliminating obvious small room key's, meaning the first reflections, and introducing key's from a larger room I can change the perception of the stereo sound being reproduced. Getting closer to how it should sound in a better room. Jim's version will be more pure than mine, no doubt. I'm just trying to figure out our perception of sound and having a blast in the process.
The differences in perception with or without added ambience are not small. Both of our attempts are (more or less so) based on available concepts. With the difference that each of us is trying to maximize that goal for our particular listening environment.
For me, personally it is clear if brings an advantage over the traditional stereo listening experience. I do play with 5.1 mixes from time to time to compare my own efforts. But I only run 4 channels so it isn't a fair comparison. It still needs a mix down of the center and I don't run any subs. It started as a loosely implemented LEDE concept and with the help of the papers by David Griesinger it evolved a bit further. It is experimental though, at least for the most part. But there is much to learn from doing this. Luckily there is research available to guide us, but it will be taste and subjective preference that guides us as well.
I'd take a better room any day, but don't have that luxury. The next best thing in my book is to maximize what I do have. I started this road out of curiosity. It was on my agenda from day one starting this project due to the experience of reproducing stereo in an even smaller room, my Car. I wasn't able to get any meaningful results there due to lacking DSP channels but I wanted to know what this concept could do. I prefer the listening experience with the added ambience. Still experimenting to dial everything in though.
But I do believe there are differences between what we are doing and a multichannel upmix. The both of us are trying to compensate for our listening environment, making the room behave more like an ideal listening environment. I am extremely handicapped compared to Jim as I am using a living room. But by eliminating obvious small room key's, meaning the first reflections, and introducing key's from a larger room I can change the perception of the stereo sound being reproduced. Getting closer to how it should sound in a better room. Jim's version will be more pure than mine, no doubt. I'm just trying to figure out our perception of sound and having a blast in the process.
The differences in perception with or without added ambience are not small. Both of our attempts are (more or less so) based on available concepts. With the difference that each of us is trying to maximize that goal for our particular listening environment.
For me, personally it is clear if brings an advantage over the traditional stereo listening experience. I do play with 5.1 mixes from time to time to compare my own efforts. But I only run 4 channels so it isn't a fair comparison. It still needs a mix down of the center and I don't run any subs. It started as a loosely implemented LEDE concept and with the help of the papers by David Griesinger it evolved a bit further. It is experimental though, at least for the most part. But there is much to learn from doing this. Luckily there is research available to guide us, but it will be taste and subjective preference that guides us as well.
I'd take a better room any day, but don't have that luxury. The next best thing in my book is to maximize what I do have. I started this road out of curiosity. It was on my agenda from day one starting this project due to the experience of reproducing stereo in an even smaller room, my Car. I wasn't able to get any meaningful results there due to lacking DSP channels but I wanted to know what this concept could do. I prefer the listening experience with the added ambience. Still experimenting to dial everything in though.
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Thanks for the clarification Jim.
I agree that the goals of stereo reproduction are rather loosely defined. Some recordings are exceedingly dry and rely exclusively on listening room acoustics to generate ambience. Other recordings include extensive ambience which may work against natural room acoustics - or your chosen DSP acoustic. Some are optimized for headphone reproduction (a fringe area, but still - don't get me started on the moving target that is headphones!)
Certainly, the acoustics of the typical domestic listening room are not preferable for creating this ambience or spatial impression from a 2 channel source. So I understand why and what it is that you are doing (using additional channels to create a 'better listening room' spatial impression). Yet, I fail to see how it differs functionally or even philosophically from upmixing stereo to 5.1. In the latter case, one is adding ambience - artificial listening room ambience in your case (not necessarily "recovering ambience") - and reproducing this upmix on a standard 5.1 setup. The only difference is that the placement of the speakers is not standardized in your setups.
In your solution to the ambience problems of 2 channel reproduction in small rooms, the ambience, although artificial, cannot be chosen by the artist and tailored to the content. In "pure 2 channel" stereo, this is an unavoidable limitation. But since you are already dabbling in surround sound upmixing (even if only to the end of enhancing stereo listening room acoustics), it may be worthwhile to consider the well thought out, standardized formats for surround sound, which was also designed to solve these same problems (among other things). If you were using a standard 5.1 setup - even with your own custom stereo upmix as you are using now - you would at least allow for the playback of content designed for this situation: discrete reproduction channels for artificial ambience.
I understand and agree that 2 channel music greatly benefits from ambience in the listening environment. Yet, this "playback ambience" is not defined, and cannot be defined, within the constraints of the stereo format. "Treated small room" 5.1 basically solves these problems (listening room does not create desirable ambience, artist has control over ambience reproduced in playback environment).
All that said, I think it is quite interesting stuff that you are doing, coming from an understanding of the shortcomings of stereo reproduction in small rooms, and surely is giving me food for thought...
You make some compelling points. But let me clarify my intentions still further.
Speaking of my situation only, my reason for adding ambience is largely a consequence of my room treatment. Let me explain.
In my efforts to minimize early (<20ms) reflections via room treatment, I have deadened or eliminated most of the later arriving ones. My ambient project is mostly about reintroducing these later arriving reflections (energy) that my room treatment has eliminated.
Therefore, I would characterize what I am doing not as an enhancement, but as recovery. So in my way of thinking, what I am doing is only an extension of treating the room, not meant as a pseudo alternative to 5.1.
Nor is my attempt meant as an alternative to 5.1. At least not in the sense as an upmix of logic 7 would be. More like Jim, I'm substituting new sound reflections for the ones I robbed away with damping.
Without damping the wall behind the listening position I get some of the same effects as I get with the ambient info. But the reflections come too soon in my small room and it takes too much away from the clarity and focus.
With the damping and ambient channels I regain what was positive about the rear reflections without sacrificing the clarity etc. It "feels" like a larger space. Still very much depending on the played content I have to say.
Without damping the wall behind the listening position I get some of the same effects as I get with the ambient info. But the reflections come too soon in my small room and it takes too much away from the clarity and focus.
With the damping and ambient channels I regain what was positive about the rear reflections without sacrificing the clarity etc. It "feels" like a larger space. Still very much depending on the played content I have to say.
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I'm glad to hear that this has been an effective way of creating an "ideal room" within a "less than ideal room". A creative solution to the overly dead sound that comes along with eliminating small room cues... I am a fan of the concept for sure.
I maintain that surround sound as a physical configuration, and a delivery format, has better potential for being transported into the mix, or recreating the exact ambience of the recording venue (for purist reproduction). A 5-channel speaker configuration with the surrounds placed 90 degrees +- 20 from center is near-optimal for creation of large room ambience in a small room, according to research cited by Toole in his book. (Ambience arriving from the sides is the most effective at generating immersion.)
In terms of creating a better listening environment for 2 channel stereo material - one more akin to the configuration of a 2 channel mastering studio, or a no-expense-spared listening room - I have no doubt that what you are doing is effective as per your subjective impressions and room measurements. I only suggest that these efforts point to the shortcomings of traditional 2 channel stereo in small rooms, and that desirable room ambience effects may be created just as well, or better, in a standard 5-channel or 7-channel configuration, or even one lacking the center channel (while also having the benefit of compatibility with content created with these extra channels in mind).
Home theater speaker layout - 5.1 and 7.1 recommendations from Dolby, THX and ITU - Acoustic Frontiers
A creative solution to the overly dead sound that comes along with eliminating small room cues... I am a fan of the concept for sure.I maintain that surround sound as a physical configuration, and a delivery format, has better potential for being transported into the mix, or recreating the exact ambience of the recording venue (for purist reproduction). A 5-channel speaker configuration with the surrounds placed 90 degrees +- 20 from center is near-optimal for creation of large room ambience in a small room, according to research cited by Toole in his book. (Ambience arriving from the sides is the most effective at generating immersion.)
In terms of creating a better listening environment for 2 channel stereo material - one more akin to the configuration of a 2 channel mastering studio, or a no-expense-spared listening room - I have no doubt that what you are doing is effective as per your subjective impressions and room measurements. I only suggest that these efforts point to the shortcomings of traditional 2 channel stereo in small rooms, and that desirable room ambience effects may be created just as well, or better, in a standard 5-channel or 7-channel configuration, or even one lacking the center channel (while also having the benefit of compatibility with content created with these extra channels in mind).
Home theater speaker layout - 5.1 and 7.1 recommendations from Dolby, THX and ITU - Acoustic Frontiers
hi jim, I cant help, by looking at your room pictures in gearslutz, to think that your room may indeed be way to dead.
From I can see from your treatment, and correct me if im wrong, is that you have a lot of absorption that are not covered with a membrane that reflect the highs?
I understand that for first reflections panels, a HF reflective membrane in front of your first reflection panels is obviously not wanted, but for all the other absorption panels in your room that you have, shouldnt you put diffusion over your absorption panels in order to not make your room too dead?
I once covered my whole back wall with floor to ceiling absorption and it sounded horrible indeed because it made my room way to dead...
One of the room that interest me most at gearslutz is Boggy's room. im sure you know his room, but unless you dont, he has something like 10 to 100cm of absorption all around the room, and a false wall made of wood slats that cover them all in order to allow the room to not be overly dead.
https://www.gearslutz.com/board/studio-building-acoustics/581809-myroom-acoustic-design-2.html
post #36
From what Ive read, the solution of very deep absorption covered by wood slats seem to be overall the best method (albeit the most expensive), or maybe im wrong. what is your take about this method and dont you think you would have better result?
thanks
With my ambient speakers going, my Rt60 is in the .25 - .30 range (>300hz). Hardly dead.
If you want to talk about my room specifically in detail, it would be better over at Gearslutz (see thread link below my post).
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Did you guys catch Pano's cave? http://www.diyaudio.com/forums/multi-way/269864-caveman-speakers-troglodytes.html
If you look at his ETC:
http://www.diyaudio.com/forums/multi-way/269864-caveman-speakers-troglodytes-6.html#post4519064
Maybe we should all have a cave like that to play with...
If you look at his ETC:
http://www.diyaudio.com/forums/multi-way/269864-caveman-speakers-troglodytes-6.html#post4519064
Maybe we should all have a cave like that to play with...
Did you guys catch Pano's cave? http://www.diyaudio.com/forums/multi-way/269864-caveman-speakers-troglodytes.html
If you look at his ETC:
http://www.diyaudio.com/forums/multi-way/269864-caveman-speakers-troglodytes-6.html#post4519064
Maybe we should all have a cave like that to play with...
Thats about what my ETC would look like without a kicker or ambient speakers.