This isn't meant to start a fight, but it is important to on lookers. As a qualifier, I have my own audio forum where we report on audio issues as we empirically test them. It helps us short cut on theories and developing methods of listening. We have a wide range of systems and they are all over the world adding their experiences to the mix. Some are engineers, some are artist and others are audiophiles both new and old. One question I am almost always asked while I am visiting other forums, from some of my members and also members of the forum I am visiting is, why do so many HEA hobbyist talk theory without any, or very limited, empirical testing or experience?
I have been around empirical testing labs since I was a kid, and one thing that is certain is, you can always tell if someone is talking without walking. Right now on this forum there are easily 20 threads going on where folks are talking theory and there is absolutely no doubt to any of us who have actually done the testing needed, that the guy talking has never done the actual empirical testing themselves. I've seen this happen with HEA reviewers and designers and a ton of hobbyist. My question is this, why?
You would think that this hobby would be about listening and experience, so why are there so many myths created and why, in this hobby in particular, do people claim they know something without ever experimenting or being part of a team of empirical science folks. It's not that hard to setup a real empirical testing ground, so why don't we see this happen?
I'm not asking for peoples credentials, and I'm not asking to be trolled, I'm simply asking why talk and not walk? In many ways HEA is on pause while the rest of audio innovation is moving forward. I'm also not asking you guys to defend HEA, we've all heard it been there done it. What I'm asking is a very simple question in a hobby that is suppose to be based on "doing", why fake it?
I said it before and I’ll say it again. What type of wave is a sound wave? In this case, the particles of the medium move parallel to the direction that the pulse moves. This type of wave is a longitudinal wave. Longitudinal waves are always characterized by particle motion being parallel to wave motion. A sound wave traveling through air is a classic example of a longitudinal wave. Hel-loo!
I've been tuning for many years, so maybe it would be helpful to some of the people reading this if I talked a little about my own experience. Like most everyone else, I got started with tuning because I was looking for better sound. I felt that what I had was ok, but I wanted more. I began with acoustical treatments and then moved into stripping down components, using minimalist wires, and tweaking the electricity. At this point in time, I really can't NOT tune a system. How do you listen to a component with its chassis top on when you know that removing it will give you a sound that is so much more dynamic and open? How long can you look at a capacitor strapped down with a plastic zip tie, when you know that freeing it will give you a three dimensional, holographic soundstage? If it's me, the answer is - not long at all. :)
As my systems became more finely tuned over the years, I began to notice that recordings I remembered as all sounding reasonably good differentiated into a large group of recordings that sounded spectacularly good, and a small group that didn't sound anywhere near as good. What I also observed was that if I put together two equally good sounding systems from different components, the same recording could sound wonderful on one system and ho-hum on the other. It wasn't the recording. At this point, I could have done one of three things: One, dial the system back until all recordings sound just ok. Two, live with the tuned in system that does most recordings extremely well and ignore the recordings that aren't so great. Or three, tune the system to the recording.
I'd like to say that I've been in camp number three all along, but that isn't true. Opening a system up by stripping down components, using good platforms and good wire, careful setup of speakers and room treatments, and releasing tension from the electrical will get you to spectacularly good sound. But tuning to the recording is really a different skillset. It's the same tools and techniques, but you need to understand what sonic effect each move has and then put together the right combination to get yourself where you want to go. With so many variables involved, it was really more than I felt I could do.
What changed things for me was the discovery of the Audolici A25M. The Audolici is an integrated EL34 tube amp that makes about 30W per channel. It's a lovely sounding amplifier even untuned, but what really sets it apart is its ability to be tuned to the recording with wooden blocks under its chassis. What this means is that recordings that had sounded distant, unfocused and uninvolving can be tweaked into sounding beautiful in just a few minutes. And the spectacular recordings sound just as spectacular as ever, with their own settings. Essentially, what had been a complex process involving many different parts is now reduced to an adjustment on a single component.
In practice, I find I don't actually need to retune for every CD I put on. Many recordings will sound at least good to very good with the same block setting under the amp. But when I put on something that has a distinctly different recorded 'key', I'll know it inside of 10 seconds, and I adjust the blocks until I get the sound I know was in there. :)
I know there will be people who read this and have no interest in going down this road. Believe me, there's no judgement. Every person needs to decide for themselves what great sound is, and how far they're willing to go to get it. I'm just telling you about what has worked for me.
testpilot 182 posts 05-15-2018 9:30am The sound gets refracted ("back" removed) towards the listener due to the change in the transmission medium i.e. hot and cold air
>>>>>I want to get on board your explanation. I really do. Can you be a little more specific and go into detail just a bit? So far I’m thinking hmmmm, maybe partial credit.
It’s based on the same principle as why can we hear sound for longer distances in winter than in summer. You have already given the theory as to the why and how in the post above.
>>>>Not exactly. You’re close. Very close. The analogy is why we hear better from across a lake on a cold morning rather than later in the day. It’s because the temperature of air higher up above the lake is warmer than the air closer to the lake surface. And sound travels faster in warm air. Thus, sound waves higher above the lake surface up fall over the slower sound waves lower down and bend down toward the listener. So he hears better than if there were no temperature gradients. There would be no temperature gradients in winter or in summer generally speaking. Except fir the case I gave of a cold morning and warm afternoon. The temperature of air near cold lake water slows the speed of sound. In the afternoon the temperatures above and near the lake surface are more equal.
I already stated my pant legs were not flapping in the breeze. So obviously there is no movement of air as if there was a draft. But if the air is compressing and expanding the air molecules must be moving. If the air molecules were stationary the air would not compress or expand. PV = nRT
theaudiotweak Not upset. Gotta catch a plane home..later..but until that time keep looking and hunting. Shear is all around..just not understood by many. Tom
>>>>>I can hardly wait. So shear is like what, love? Did Einstein understand it? Or only you guys?
He knows. Even the janitors at Nasa know! Don’t you realize GK just likes to say things to see if anyone is paying attention to him? Very attention starved! Must have had a tough childhood. Poor guy!
My wife can detect the slightest draft. Next time I get things cranking, I’ll close the windows or turn off the AC and check with her. She will know if the air is still flowing for sure!
Tom, sorry if I upset you. Please explain what you mean. By shear and Polarity and how there’s no such thing as isolation. You just keep repeating the words as if they are self explanatory. Type slow since I’m from NASA.
Sorry you cannot learn or understand anymore as you are truly isolated in thought.
Your brain has about the same shear velocity and density as lead. NASA must have been happy to eject you because your days of grandeur are more like delusions. Tom
Then don’t over damp it. Hel-looo! Don’t throw the baby out with the bathwater. There’s a right way and a wrong way to do everything. You’re obsessed with rubber and rubber tires. Expand your mind. Besides it’s not that tires that are isolating the car. And don’t start up with the old but there’s no such thing as isolation routine. That got old a long time ago. Almost as old as shear.
Unfortunately Mr Green apparently has chosen to not shed any light here on any of this. Too bad. The answers would appear to require a road trip to his very interesting web site.
Damp those vibrating solids. Vibration and resonance are the enemies of great sound. That or the audiophile must "manage" the nature of those kinetics.
WOW! This thread is a perfect example of how science does not and will never account for what our ears hear. "Fake Science"!
(Edit): Is that the kind of empirical understanding promoted at the Michael Green site?
BTW, I agree with your assessment of Green’s behavior in this thread , obviously. Labeling anyone who challenges your claims "trolls" instead of simply responding to the arguments is never a good look.
As you can see: anyone can make up, or infer, any hypothesis they want. And if the method of "testing" the hypothesis is merely subjective, then the results can be confirmed by the imagination of the subject. Hence...you have endless tweaks based on wild hypotheses being "confirmed" because "I heard the difference!"
WOW! This thread is a perfect example of how science does not and will never account for what our ears hear. "Fake Science"!
BTW...Michael, I still have all corners of my listening room treated with your products and they make a substantive difference to my listening enjoyment. Sadly, this thread has impeached your character in the way you negatively label those who don't say what you wish them to say. Sad.😞
The reason it’s said that you want a large size woofer or large excursions of the diaphragm is because it pushes more air is uh, it pushes more air. The air moves. Hel-loo! As I said acoustic waves require air to propagate, analogous to waves on the ocean. The air molecules like the water molecules are moving, at least when the wave pushes through it. So when an acoustic wave hits a wall, air molecules are moving. It’s the frequencies of the of the (complex) wave that we hear and that produces resonance of objects in the room, not of air molecules. A standing wave has a frequency, although the air molecules at that location move along with the wave. Reflected waves have frequencies, the air molecules resonate at whatever frequency or frequencies the wave is moving. In a sense you cannot separate the acoustic waves from the air, there would be no sound without air. In space no one can hear you scream.
Wrong. You are conflating flow and vibration. The air particles in the room vibrate elastically at musical frequencies they do NOT “flow” around the room. There is no net air movement Flow = Zero, Capiche?
But there is air flow in the listening room, you silly goose. 🦆 For heaven’s sake, don’t have a conniption. 😫 The air molecules are pushed by the high speed acoustic (mechanical) waves, just as waves in the ocean push the water. So, there is laminar flow in the room, and in many directions, obviously. There would not be resonance without mass and there would not be mas without air molecules.
Some examples where baffles are used to organize or maintain laminar flow for audio applications include air baffles for air tubing for my air bearing everything Maplenoll turntable, 500 feet of air tubing, between the air compressor and the air bearing platter and air bearing tonearm AND a small baffle in the air spring connecting air fitting between the auxiliary air canister and the air spring per se, maintaining a smoother flow of air during operation, the air flow velocity in this case must certainly be quite low, no?
Fellows you should study up on shear waves and their various velocities and polarities thru and on all solid materials in your listening room including solids in motion. Compressive becomes shear...on impact..or on solids in motion.Tom
Since there is no air flow in a listening room you can’t create turbulent flow. You don’t even have laminar flow in a listening room.
Reynolds numbers?
Good grief.
We have such a conflation of different applied sciences here - none of which applies to audio! We are venturing into aerospace engineering and motor vehicle drag perhaps but this is nonsense in audio.
Waves on a beach? Good grief - waves in the sea are NOT elastic acoustic waves at all. Again conflating completely different phenomenon. Surface waves at an interface have orbital progressive properties. The interface is key - just like the major damage from earthquakes comes from “ground roll” at the interface.
The reason acoustic energy varies in a room is due to the reinforcement and interference of a multitude of reflected acoustic waves along with the primary. Since the reflection surfaces are rigid compared to air there is also a build up of pressure very close to the wall. Listeners should keep at least 3 feet from a wall - 6 feet is better.
The sound gets refracted ("back" removed)
towards the listener due to the change in the transmission medium i.e. hot and
cold air
>>>>>I want to get on board your explanation. I really do. Can
you be a little more specific and go into detail just a bit? So far I’m
thinking hmmmm, maybe partial credit.
It’s based on the same principle
as why can we hear sound for
longer distances in winter than in summer.
You have already given the theory as to the why and how in the post above.
I do believe the whole subject of room issues is very real and goes way beyond what alot of people work at with bass traps and wall diffusers etc. After all you only need look at some websites to see what some are selling just as off the shelf items, And I do believe certain people spending years in the research and counterpoint of these effects has been productive. I wonder though with the wave of the latest electronic correction devices if this has somewhat negated all of this effort?
I wonder just what effect a unit like the Lyngdorf 2170 or Anthem would have on the rooms that already been heavily massaged and tweaked? Would they be able to improve still further? Or would they possibly make matters worse? Be interesting to note the amount of room correction they attempt to make.
Personally I have known my room was acoustically terrible for years but then came along the 2170 and as far as I am concerned it did the "walk" for me and in all honesty I am just about done and really just sit down and enjoy the music for hours on end. Maybe ignorant bliss and contentment but its my room...lol.
glupson, as a matter of fact Michael and I both talk the talk AND walk the walk. He and I have both been exploring room acoustics for a very long time, independently. He and I have spent extraordinary effort and time finding out how things work. I was one of Michael’s first customers around thirty years ago and have measured the effectiveness of his Echo Tunes and Corner Tunes. Of course many others also were getting their hands dirty and developing products.
I designed and developed quite a number of room acoustics devices that address a wide range of room acoustics problems. My very first product was going to be Ortho Ears for improving dynamic range, modeled after Mr. Spock’s ears, but that product was overcome by events, perhaps fortuitously. Off the top of my head I have at least SEVEN room acoustics products, including some quantum mechanical ones. I developed the first comprehensive crystal-based product line for resonance control and room acoustics control. I have also spent much time and effort studying room acoustics dynamics, including mapping out the sound pressures of the entire 3D space of the room. I have built my own Helmholtz resonators of various sizes, including a 15 foot long folded horn resonator for very low frequencies. I have my own ceramic version of the tiny little 1” bowl acoustic resonators. My hands have not been soaking in Ivory liquid, Junior.
Getting back to the whole laminar flow issue for a second, we know that air moves in the room while music is playing. We also know that acoustic waves themselves travel through air at the speed of sound. These high speed acoustic waves striking a surface would be like waves of water striking the beach, no? So the dynamics of the acoustic wave + air hitting a surface would obviously have a much greater impact than one might imagine. That’s why I measure sound pressure peaks in some locations around the room that are 10 times higher than the average sound pressure in the room. That’s a lot of energy, no?
That is the beginning of what I was thinking about in my hypothetical room, or let’s say that room that you had copied the article about. Although, I was, in my mind, playing with multiple variables of the equation. I was mostly wondering about density and that was, in fact, how I imagined the change in Reynolds number. You picked viscosity. All the same for practical purposes of theoretic imagination. I envisioned different air composition. In my thoughts, I used Helium. I guess 80/20 would be preferred. That led me to thinking what happens to the sound perception (actually, I called it simply "sound") with changes in density of the medium and how it would affect the direction, energy transfer, and whatever else may be involved. Even that unfortunate laminar flow would be greatly affected or enhanced so, if it actually matters, it would affect the sound based on that fact, too. I went through those mind exercises without coming up with any conclusion I would be able to stand behind, but it was a fun exercise for me. Sure, it would be quite complicated to do it in real life, not impossible but prohibitive on more than one level. Making a room Helium-tight would be a decent challenge. For most, just the price of HeliOx would be ridiculous even for a relatively small room (and the one I was imagining was the one on the picture on MG’s website next to where laminar flow is mentioned and it seems quite large). I think that canister is around $700, but may be very wrong about that one. You would likely need many of them. All in all, it was just an exercise, not anything I would consider doing. I was not thinking of change of Reynolds number as means to enhance laminar flow (although that is how I remembered it at first), but as a product of changed density. In my mind, I changed the density which then changed the Reynolds number, and conveniently that would also do something to flow characteristics, in case anyone is interested in that part.
However, it all did come to me from my post you may not recall. In it, I mentioned how I was interested in what methods Michael Green uses to determine where to place his shutters as it seems impossible that placing them in the same position in different rooms would yield same results. You could get it by luck, but then you could also just throw a few pillows around and call it a day, too. That is when I mentioned I find it hard to imagine how it may be done because I would guess it would require equipment and staff for laminar flow measurements and then doing it at different heights and temperatures which I cannot imagine being very convenient even for a well-run business. I may be wrong on that. Temperature was that link from Reynolds number as it, as you pointed out, affects at least viscosity. That is why I actually did stop and think about your ice-cold water for a moment.
Velocities in any kind of listening room are probably very low and likely cannot be greatly influenced, but viscosity and density could, as above. However, there will practically always be some turbulent flow of air in a vessel, in our case the vessel is listening room. If the walls are perfectly smooth, paints differ wildly on that one I just learned, turbulence will increase with distance from the wall, making the middle of our listening room the most vulnerable spot. Of course, add a chair or two and all bets are off. I speculate that, barring a hurricane in the room, turbulent flow will not have much influence on the propagation of sound. I am not saying none, but not much. Of course, for this purpose anything may be important.
That all was just trailing on my initial question about "organizing laminar flow". All of this above had nothing to do with that initial question, but it somehow got out of hand when I thought of it.
The more I think about that "organizing laminar flow", the more I am getting a feeling it is just poor choice of words. Not that I am a firm believer in it for CD-listening purposes, but am focusing on basic statement I read on website.
I am sorry if all of this above is not written clearly, I just wrote as fast as I was thinking about it and as fast I could write it, I did not edit it as it is very late.
For the purpose of this thread, I just talked the talk. If anyone is willing to walk the walk and do what I imagined above, I will humbly admit you are a real walker.
Turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce chaotic eddies, vortices and other flow instabilities.
The Reynolds number Re is defined as,
Re = fluid density x fluid velocity x characteristic linear dimension / dynamic viscosity of the fluid
where:
ρ is the density of the fluid (SI units: kg/m3) u is the velocity of the fluid with respect to the object (m/s) L is a characteristic linear dimension (m) μ is the dynamic viscosity of the fluid (Pa·s or N·s/m2 or kg/m·s) ν is the kinematic viscosity of the fluid (m2/s).
Reynolds number is proportional to the velocity of the fluid (air) which is rather low in a listening room, so Reynolds number will be relatively low. I don’t recall my pants legs flapping in the breeze whilst listening. It’s not exactly a wind tunnel. So turbulent flow is very unlikely or perhaps impossible. This is not to say there might be some advantage sonically to “organizing” laminar flow using shutters. Remember organizing laminar flow doesn’t mean there has to be turbulent flow or that turbulent flow is prevented.
I personally would have to experiment with the shutters to see what happens sonically. The viscosity of the air in a given room will be fairly constant except in the case of bowls of ice cold water, one or two or three or more, that I mentioned, in which case the viscosity and thus the Reynolds number will be different lower in the room than higher up. Reynolds number is mostly a function of temperature. And the speed of sound is slower in cold air than warm air. Therefore the part of the acoustic wave higher up in the room will be faster than lower down so that the wave will bend over and down toward the listener position. He will hear more of the sound, especially the treble, including ambient information. But because of the speed of sound issue not really Reynolds number.
I kind of enjoyed this thread. Probably due to its bizarre turns. There were inexplicable characters, weird responses ("your adult diapers are elastic", or something to that effect), some concise and sharp observations, strange non-questions, a few topics completely unrelated to the original one floating around at random, a little bit of basic physics ("what is sound"), some pointers to other websites, one potentially interesting link on youtube (even if it was me who posted it), and food for my own thoughts rising from all the jungle I just mentioned. It was all quite entertaining. I learned, prompted by the thread but not in it, about some design features of airplanes, paint quality issues, how drums get tuned, botany (Nevada trees), CD-making process, dynamic ranges of albums I have, and a few more things. I have to give Michael Green credit and thanks for that. Had I started a thread, it would have died after a post or two. As this is supposed to be "hobby" website, I consider coming here "waste of time" or "entertainment" so I will have to admit that it served the purpose. All along, while following discussions on audiophile website Audiogon, I sat in silence or, at best, listened to Internet radio on $50 Bluetooth speaker. Not that I did not need room tuning, I probably would not have been considered worthy of logging in. Life is good. Just do not take it too seriously. I am sorry you got so upset.
I honestly think a thread like this can be, and to some degree has been, turned into something somewhat valuable. I think it’s a good thing to identify the types of posts that are "bad faith" style posts, including the follow up replies.
I think if someone has a problem with a specific person, argument or claim, he should be specific about it. At least supplying examples. Otherwise it’s just an excuse to lodge gripes without being challenged on them, and therefore not showing openness to the idea you are wrong, and letting someone make the case you are mistaken.
And that’s not to mention the undercurrent of self-advertising that puts a stink into the noses of many people reading such threads.
I certainly defend the right of high end audio salesmen and manufacturers to post here, as they can contribute valuable information. (Geoff even contributed to one of my threads asking about turntable isolation, and I appreciated that!)
But I don’t think it should be at the price of those people always going unchallenged, if they are making critiques, gripes or bad-faith posts, and disguising advertising for their own web sites or products as dialogues about something else.
(And I’ve had people telling me I’ve given voice to their own feelings about this thread, so I'm comfortable that it wasn't "just myself" that I was arguing for).
I just noticed your post and am glad I did not end up being a troll. I do think that both you and prof have taken your arguments too seriously. I tried to stay in the middle, focusing on more tangible things.
do not take it too personally. You could not win. It seems that I became a troll, too, despite fully in good faith trying to explain why people cannot afford trial and error approach on everything. In fact, many would agree that it would be foolish. I am only sorry that I never got my answer about laminar flow as advertised on the website. It is baffling me.
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