Hi Juergen,
No, you read it wrong. There are psychoacoustic studies on perception of reflections but none on music reproduction in small acoustic spaces. Naqvi is the only one I know of that came close. But Blauert is on of the single most knowledgeable people in that field, so I wouldn't be so bold to act arrogant and call it just a belief.
You don't need to. Why not try something else, e.g. cooking, be nice to people, etc.
That was a good one. Nowhere near. What is the German reference sound pressure level for reproduction of "serious recordings"?
Best, Markus
xpert said:
No, you read it wrong. There are psychoacoustic studies on perception of reflections but none on music reproduction in small acoustic spaces. Naqvi is the only one I know of that came close. But Blauert is on of the single most knowledgeable people in that field, so I wouldn't be so bold to act arrogant and call it just a belief.
xpert said:
You don't need to. Why not try something else, e.g. cooking, be nice to people, etc.
xpert said:
That was a good one. Nowhere near. What is the German reference sound pressure level for reproduction of "serious recordings"?
Best, Markus
It's a pity that so much good technical input is being drowned in personal stuff. Zilchlab, take a break from this thread for the next 48 hours. xpert, we're going to take some other action. All others, please keep things to the technical level, not personal. Forum rules. No argument.Done....SY said:
fb said:
Sure. Keep in mind that this is just a proof of concept. It only does 40 slices from back to front and it assumes the angle at the throat is 0. You could do all the fancy stuff with more work but you'd really want to do that in a CAD program if you were planning to CNC a mold.
markus76 said:
You know that Blauert won't "hypothesize" if its not cold hard fact then he is very cagey about his responses.
markus76 said:
Unfortunately I am firmly of the beliefe that multichannel will not gain acceptance as a mainstream format. This means that we can't simply ignore 2 channel because it is not ideal. I am very much a 2 channel person and seak to optimize its performance as much as possible.
markus76 said:
So you know him? Wow!
Blauert is THE authority on binaural hearing. While not the most congenial person I have ever met (I mean after all he is GERMAN 🙂 ), I have nothing but the utmost respect for him and his work. He is extremely thorough. If he says that something is fact, it is!
A sharp contrast is Brain Moore, who if you met him in a pub you might think him a hippy bum. He is a very nice guy who likes to sit and stum his guitar.
Now that we have gotten the flame wars settled out, I wanted to post my honest opinion about waveguide vs. horns and HOM.
I have listened to horns for more than 40 years. Basically thats all I have ever owned. They have their pro's and cons, but I like so many, found that they had a sound quality that can sometimes grate on your nerves - its often called harshness and I find this an appropriate term. Now, not I, nor anyone else, can tell you exactly what harshness is or how to measure it, but certainly no one will deny that it is real.
I spent a great deal of effort over the last several decades on trying to understand this poor quality, because, quite frankly, in every other aspect horns beat all other types of HF sources hands down.
Some thirty years ago I started to study horns in detail, but it didn't take too long to figure out that analytically (mathematically) they were sadly lacking. There were some asumptions made that everyone knew weren't true, but everyone just kept on using them anyways. I wasn't satisfied with this lack of understanding so I dug a little deeper. And then it dawned on me that what was needed was a more complete mathematical description of the performance of a horn - and waveguide theory was born (thats now all in print and well accepted). This new approach predicted some radically new (for the time, about 20 years ago) profiles. There were some early attempts at using the new concepts but they weren't very sucessful and for all practical purposes the ideas laid dormant for a number of years. Some of the concepts were begining to be used, like mouth radi to reduce mouth diffraction, etc. but no one was actually making true waveguides according to my original work.
When I left Ford about ten years ago I decided to renew my interest in the concepts. I built some waveguides and low and behold, they actually did sound better - to me at least. But they also measured better. Back in the early 90's, John Eargle, who was good friend and had a strong interest in my work, commented that JBL had built some waveguides and found that the impedance (electrical) of the devices was very smooth - none of the multiple ripples found in the diffraction horns of the era. He commented on how much of an advantage this was to a passive crossover. Years later I was to see this advantage in practice.
While the waveguide themselfs were a big improvement, it was not until I tried a foam plug that I really heard something that got my attention. ANYONE who has tried foam will tell you that the difference isn't small - its major. Needless to say I was intrigued. I wanted to understand why this simple device worked so well. As I looked into the situation further I begain to put together a corherent concept of what might be at play here - namely the HOM (I had discovered that distortion wasn't a factor as I had though at first - see the B&C paper). The new theory had predicted that HOM would exist and there is now little doubt that they do, but is this the sole answer to what makes the new devices sound the way that they do? Quite honestly, I am not sure.
ALL of the data that "I" have says that the HOM and the internal reflection reductions are what is making the difference. However, I am still NOT convinced that this is ALL there is to the story. That HOMs are part of the story, I have no doubt, that they are the whole story, I am far less confident. In fact I have some pet theories on what else it might be, but alas those are not for public consumption at this point.
So in a nutshell, I have spent nearly 30 years trying to improve the sound of a horn. I believe that I have done that. What exactly is it that I have done to make this difference? - first, better contours than have less diffraction and edge treatments that create less reflections and diffraction. These things CAN be measured and with some experience its possible to see them in a set of data. I see them, but clearly not everyone else does.
Second there is the foam plug. Exactly what this does is not yet clear, but damping of the undesirable waves is certainly part of it. But there might be other aspects to it as well. Measureing these effects IS NOT easy and even I have not found the "smoking gun" as to exactly what is going on. That the foam plug is not some audiophool psuedo-science can only be truely stated by those who have actually experinced it. I have not heard a single person say that they did not hear a difference, and further, that it was not an improvement. But of course this later data is all circumstantial at this point. And its likely to stay that way for a fairly long time. Thats just the way audio is.
I have listened to horns for more than 40 years. Basically thats all I have ever owned. They have their pro's and cons, but I like so many, found that they had a sound quality that can sometimes grate on your nerves - its often called harshness and I find this an appropriate term. Now, not I, nor anyone else, can tell you exactly what harshness is or how to measure it, but certainly no one will deny that it is real.
I spent a great deal of effort over the last several decades on trying to understand this poor quality, because, quite frankly, in every other aspect horns beat all other types of HF sources hands down.
Some thirty years ago I started to study horns in detail, but it didn't take too long to figure out that analytically (mathematically) they were sadly lacking. There were some asumptions made that everyone knew weren't true, but everyone just kept on using them anyways. I wasn't satisfied with this lack of understanding so I dug a little deeper. And then it dawned on me that what was needed was a more complete mathematical description of the performance of a horn - and waveguide theory was born (thats now all in print and well accepted). This new approach predicted some radically new (for the time, about 20 years ago) profiles. There were some early attempts at using the new concepts but they weren't very sucessful and for all practical purposes the ideas laid dormant for a number of years. Some of the concepts were begining to be used, like mouth radi to reduce mouth diffraction, etc. but no one was actually making true waveguides according to my original work.
When I left Ford about ten years ago I decided to renew my interest in the concepts. I built some waveguides and low and behold, they actually did sound better - to me at least. But they also measured better. Back in the early 90's, John Eargle, who was good friend and had a strong interest in my work, commented that JBL had built some waveguides and found that the impedance (electrical) of the devices was very smooth - none of the multiple ripples found in the diffraction horns of the era. He commented on how much of an advantage this was to a passive crossover. Years later I was to see this advantage in practice.
While the waveguide themselfs were a big improvement, it was not until I tried a foam plug that I really heard something that got my attention. ANYONE who has tried foam will tell you that the difference isn't small - its major. Needless to say I was intrigued. I wanted to understand why this simple device worked so well. As I looked into the situation further I begain to put together a corherent concept of what might be at play here - namely the HOM (I had discovered that distortion wasn't a factor as I had though at first - see the B&C paper). The new theory had predicted that HOM would exist and there is now little doubt that they do, but is this the sole answer to what makes the new devices sound the way that they do? Quite honestly, I am not sure.
ALL of the data that "I" have says that the HOM and the internal reflection reductions are what is making the difference. However, I am still NOT convinced that this is ALL there is to the story. That HOMs are part of the story, I have no doubt, that they are the whole story, I am far less confident. In fact I have some pet theories on what else it might be, but alas those are not for public consumption at this point.
So in a nutshell, I have spent nearly 30 years trying to improve the sound of a horn. I believe that I have done that. What exactly is it that I have done to make this difference? - first, better contours than have less diffraction and edge treatments that create less reflections and diffraction. These things CAN be measured and with some experience its possible to see them in a set of data. I see them, but clearly not everyone else does.
Second there is the foam plug. Exactly what this does is not yet clear, but damping of the undesirable waves is certainly part of it. But there might be other aspects to it as well. Measureing these effects IS NOT easy and even I have not found the "smoking gun" as to exactly what is going on. That the foam plug is not some audiophool psuedo-science can only be truely stated by those who have actually experinced it. I have not heard a single person say that they did not hear a difference, and further, that it was not an improvement. But of course this later data is all circumstantial at this point. And its likely to stay that way for a fairly long time. Thats just the way audio is.
catapult said:
Thankyou
I'd been planning a spreadsheet with the same approach, but I'm supposed to be studying.
This'll give me a head start 🙂gedlee said:
What does "optimize" mean when talking about stereo? You said it yourself: 'there will never be a "one size fits all"'.
gedlee said:
Not really. All I can say is that he is known for being a troll. He uses multiple accounts and emails.
Best, Markus
Patrick Bateman said:
I threw together some illustrations of how the Geddes aiming concept works. Basically it shows why the speakers are cross-fired.
I am building waveguides for the Vifa ring-radiator for my car, so I put the thread on Diymobileaudio.
http://www.diymobileaudio.com/forum/diy-mobile-audio/60146-creating-perfect-soundstage.html
"Unfortunately I am firmly of the beliefe that multichannel will not gain acceptance as a mainstream format. This means that we can't simply ignore 2 channel because it is not ideal. I am very much a 2 channel person and seak to optimize its performance as much as possible."
How can you be a Phd in acoustics and be a two channel guy?
You sell THX spec speakers and you're a two channel guy? You wrote a book on theater design! ...and you're still a two channel guy?
You must be aware of the psychacoustic advantages of surround? and you're a two channel guy?
Dr. Geddes your listening habits seem to be at odds with your education and philosophy.
BTW: Every Home Theater represents a potential multi-channel music customer, every modern car stereo owner potential multi-channel consumer, HD radio could be multichannel.
FYI: Sony is a four letter word....
For 12 years I have listened to 2 channel CD's in surround and this experience has left me feeling two channel is seriously lacking when it comes to playing back the CD. The microphone is your ears in the room during the recording process, and unless it is mounted flush in a wall the microphone has the potential to capture surround information which can be decoded off a two channel CD. Also ALL artificial reverb (ie Lexicon, Eventide, ...) and delay is modeled in a 360 degree reference which is easily decoded accurately as surround information more accurately that can be done with a two channel system. Just some quick basic items to think about. And no I don't like having the musicians behind me, its not like that when you do surround correctly.
Thanks for reading , Have a good day.
How can you be a Phd in acoustics and be a two channel guy?
You sell THX spec speakers and you're a two channel guy? You wrote a book on theater design! ...and you're still a two channel guy?
You must be aware of the psychacoustic advantages of surround? and you're a two channel guy?
Dr. Geddes your listening habits seem to be at odds with your education and philosophy.
BTW: Every Home Theater represents a potential multi-channel music customer, every modern car stereo owner potential multi-channel consumer, HD radio could be multichannel.
FYI: Sony is a four letter word....
For 12 years I have listened to 2 channel CD's in surround and this experience has left me feeling two channel is seriously lacking when it comes to playing back the CD. The microphone is your ears in the room during the recording process, and unless it is mounted flush in a wall the microphone has the potential to capture surround information which can be decoded off a two channel CD. Also ALL artificial reverb (ie Lexicon, Eventide, ...) and delay is modeled in a 360 degree reference which is easily decoded accurately as surround information more accurately that can be done with a two channel system. Just some quick basic items to think about. And no I don't like having the musicians behind me, its not like that when you do surround correctly.
Thanks for reading , Have a good day.
Without foam: http://www.htguide.com/forum
/attachment.php4?attachmentid=8931
With foam: http://www.htguide.com/forum
/attachment.php4?attachmentid=8932
It's interesting that the foam makes the initial cycles more symmetric about the horizontal axis, more like the input looks.
“Any measurements that we can look at to compare the 1086 vs Geddes "Bowls"?”
BMS 4552ND on XT1086: http://lscon.tripod.com/xt1086/
“The "Here's a measurable difference with the foam in place versus without it" approach is not getting me much of substance, as conclusions rely on an unproven hypothesis as to what's actually occurring with(in) the foam. “
It never occurred to me that the foam did anything besides absorption/damping.
Do you think anything otherwise?
“According to measurements of the XT1086, it's response is down about a half decibel at 45 degrees in the horizontal plane.”
Looks like 6 dB from ~1 kHz up in the curves at the above link.
Someone really needs to file down the neck of an XT1086 and measure it.
"I'm trying to decide if it's worth $88 to find out if that will create the "ultimate waveguide", I have an XT1086 sitting here..."
Patrick, can you do polars?
I'll chip in half the cost if it turns out bad (presuming the value is higher if it works).
Since the diffraction slot widens coverage, I'm hoping the result would be that it's CD with narrower coverage.
That would be an advantage in my long narrow room, where I want to minimize sidewall reflections.
/attachment.php4?attachmentid=8931
With foam: http://www.htguide.com/forum
/attachment.php4?attachmentid=8932
It's interesting that the foam makes the initial cycles more symmetric about the horizontal axis, more like the input looks.
“Any measurements that we can look at to compare the 1086 vs Geddes "Bowls"?”
BMS 4552ND on XT1086: http://lscon.tripod.com/xt1086/
“The "Here's a measurable difference with the foam in place versus without it" approach is not getting me much of substance, as conclusions rely on an unproven hypothesis as to what's actually occurring with(in) the foam. “
It never occurred to me that the foam did anything besides absorption/damping.
Do you think anything otherwise?
“According to measurements of the XT1086, it's response is down about a half decibel at 45 degrees in the horizontal plane.”
Looks like 6 dB from ~1 kHz up in the curves at the above link.
Someone really needs to file down the neck of an XT1086 and measure it.
"I'm trying to decide if it's worth $88 to find out if that will create the "ultimate waveguide", I have an XT1086 sitting here..."
Patrick, can you do polars?
I'll chip in half the cost if it turns out bad (presuming the value is higher if it works).
Since the diffraction slot widens coverage, I'm hoping the result would be that it's CD with narrower coverage.
That would be an advantage in my long narrow room, where I want to minimize sidewall reflections.
Another thing on modding thye XT1086 - I'm not sure how thick the walls are, but it's a pretty sharp bend, so it might require building up the outside w/metal-filled epoxy first to get a meaningful change in the profile.
I wonder if it's a weldable alloy...
Or, make a plug of the inside, then thick-walled fiberglass over that, and then have at it.
I wonder if it's a weldable alloy...
Or, make a plug of the inside, then thick-walled fiberglass over that, and then have at it.
Simpl Dug said:
The problem is, you loose important directional information once all sounds have been mixed into a two channel signal. Furthermore a single microphone is not able to capture the spatial information a multichannel solution needs in order to work. So any 2 channel upmix is just an effect and not "the real thing".
Simpl Dug said:
Unfortunately there are no reverbs that provide a complete three dimensional set of reflections (which is needed for surround to provide the most accurate virtual reality) – even today. The process is simply to complicated. Barry Blesser (inventor of the EMT-250) talks about that in more detail in his book "Spaces Speak".
Simpl Dug said:
Music industrie has no standards on that. They completely missed the train.
Best, Markus
SY said:
Thanks SY, that was overdue.
Sheldon
Patrick Bateman said:
Nice plots, but they miss a critical factor - timing. In the Geddes setup the nearer speaker gets softer as the timing gets shorter, this helps to keep a central image over a much larger area. In the "classic CD" setup the opposite occurs causing an almost immediate collapse of the image to the closer speaker. I've tried to draw this effect, but its not easy.
Simpl Dug said:
Its not MY choice! CD's are two channel! It's the market that decides these things NOT me! I do prefer GOOD multi-channel, but there is almost nothing available in that format (some DVD that I have, thats about it). I DO NOT prefer simulated multi-channel from 2 channel sources. At least nothing that I have heard here in my setup.
"optimize 2 channel" means good imaging with good spaciousness, not optimizing for either at the sake of the other.
Earl,
Your post #847 was thoughtful and very well written. Kudos to you. I for one appreciate your hard work.
Simpl Dug said ...
"How can you be a Phd in acoustics and be a two channel guy?"
I can do you one better. I am a two channel guy even tho my day job is to design and build surround gear for a company whose name you would certainly recognize. What's more, I expect that most of the engineers in the business would say the same about themselves. To be more specific, surround sound is mostly about splashing noise in support of what you are seeing with your eyes. Surround Sound is about cinema, whether it be in a commercial setting or your home. Most music is purposely recorded as a two channel experience. That is especially the case for recordings that are more than 15 years old. Audiophiles use words like 'imaging' and'soundstage' that are most meanful when listening to 2 channels. Think about it, what we call imaging and soundstage is really about reconstructing in our brains what we would be seeing with our eyes if we were watching the performance live. And when watching that performance, unless you are watching live unamplified musicians perform, chances are what you are hearing is a mostly monophonic mix delivered over multiple loudspeaker stacks (ie: No imaging) and is an entirely different listening experience with what you have at home.
I would go on to say that most emerging products such as the new 10 channel surround is mostly about marketing (ie: exchanging your $$ for their spin and paying the wages of guys like me) and mostly serves to fill in the holes made by the crappy left and right mains of your system. That is why the research that Earl has been doing is so important. Horns and now waveguides do a great job of recreating the edge and transients of a live performance. For me, Earls work is about recreating the soundfield of that live experience in a way that traditional horns cannot.
Your post #847 was thoughtful and very well written. Kudos to you. I for one appreciate your hard work.
Simpl Dug said ...
"How can you be a Phd in acoustics and be a two channel guy?"
I can do you one better. I am a two channel guy even tho my day job is to design and build surround gear for a company whose name you would certainly recognize. What's more, I expect that most of the engineers in the business would say the same about themselves. To be more specific, surround sound is mostly about splashing noise in support of what you are seeing with your eyes. Surround Sound is about cinema, whether it be in a commercial setting or your home. Most music is purposely recorded as a two channel experience. That is especially the case for recordings that are more than 15 years old. Audiophiles use words like 'imaging' and'soundstage' that are most meanful when listening to 2 channels. Think about it, what we call imaging and soundstage is really about reconstructing in our brains what we would be seeing with our eyes if we were watching the performance live. And when watching that performance, unless you are watching live unamplified musicians perform, chances are what you are hearing is a mostly monophonic mix delivered over multiple loudspeaker stacks (ie: No imaging) and is an entirely different listening experience with what you have at home.
I would go on to say that most emerging products such as the new 10 channel surround is mostly about marketing (ie: exchanging your $$ for their spin and paying the wages of guys like me) and mostly serves to fill in the holes made by the crappy left and right mains of your system. That is why the research that Earl has been doing is so important. Horns and now waveguides do a great job of recreating the edge and transients of a live performance. For me, Earls work is about recreating the soundfield of that live experience in a way that traditional horns cannot.
What page did we have Geddes OS measurements that shows with foam vs without foam?
EDIT: Nevermind, found them again.
EDIT: Nevermind, found them again.
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