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Posted by Vasyachkin on
07-18-2010
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fiogf49gjkf0d I was recently reading a book called "The Cyclist's Training Bible" by Joe Friel. The author immediately surprised me by not being an idiot. Anyway one of the things he said is that the SCIENCE of training / exercise physiology is USUALLY ONE STEP BEHIND top athletes. That it isn't the top Athletes that use science to train better but it is the SCIENCE that looks at top athletes and tries to understand how they do it. or should i say REAL science SHOULD.
I thought this was a profound observation that can be applied to many fields of human endeavor. I think in our modern society as a whole we are suffering from what i could only call "science worshipping" where scientific theory is somehow put ahead of actual reality.
For example not to get too political we have had dietary recommendations based on "scientific studies" upon following which virtually ALL of the diseases EXPLODED especially the ones that these guidelines were targeting. The fact that the results were the opposite of what they were supposed to be however didn't stop anybody from following those guidelines for ABOUT 40 YEARS because they guidelines were "scientific" and it didn't matter that it was absolutely obvious that they were wrong.
I have noticed something similar happening in Audio with respect to frequency response. People keep following the "flat = perfect" dogma despite the fact that augmented bass is ALMOST UNIVERSALLY preferred by listeners. Somehow people feel obligated to follow "science" and ignore reality.
IN FACT i have analyzed the mentality of rodents known as scientists and realized that they associate STRAIGHT with CORRECT in ALL problems. To them STRAIGHT = CORRECT is an axiom and requires no proof.
For example if you're a runner they say you must make contact with ground with your foot directly under your body ( STRAIGHT ). I just watched video analysis of a runner who kept setting world records for 13 years straight, and the scientist doing the analysis lamented that the runner doesn't quite reach the STRAIGHT geometry. well i have news for that IDIOT - it would be PHYSICALLY IMPOSSIBLE for him to do this without eventually planting his face in the pavement - but this is too technical for *scientists* to understand - they just need everything STRAIGHT.
As another example i was watching a video analysis of a Cycling Athlete's pedal stroke and AGAIN the "fitting expert" complained that the measured angle between the knee and the pedal was less than straight, which to him ( and according to official fitting guidelines ) indicated "wrong" seat position.
So this is just a heads up, lest we forget that scientists are actually IDIOTS.
When i was in college i thought scientists were smart. Now i know that the only reason we have that perception is because SMART scientists ( Newton, Einstein, Tesla, Maxwell, Faraday etc ) are the only ones we are TAUGHT ABOUT in school. Those are literally one in a MILLION. Most scientists are so dumb they make me want to stab myself with an ice pick AND on top of this they know NOTHING about what SCIENCE actually was SUPPOSED TO BE.
REAL science was supposed to explain reality, but the "science" we have today simply comes up with "guidelines" like "eat low fat" or "must be straight" or "must be vertical" or "must be flat" which represent not any sort of legitimate insight but are just a reflection of FLATNESS of the MINDS of the ones writing these recommendations.
Basically what i was trying to say is i like a lot of BASS 
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Posted by Paul S on
07-18-2010
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fiogf49gjkf0d Nice rant about "scientists"; but I suppose you are preaching to the choir here.
I jumped in not to pile on the stupid "scientists" but to address the rendering of bass, and ULF in particular, in the context of home hi-fi.
A while back I got a splash of cold water in my face when I read a post from an audio "pro" who had run actual response tests on a number of popular "subs" (and the woofers they used). I was astounded to read the rather pitiful results, including doubled McCauley 6174s that were down 3 dB at 43 Hz. Using this data and driven by renewed interest in the subject, I began to run the numbers on what it would take to get down to 20 Hz. Within a few hours, I had pretty much abandonded the half-baked "conventional" methods I had earlier half-held on to as my future (U)LF ticket.
Sometimes when I suffer a setback I develop a sort of morbid facination with the problem, itself, where I simply gather and look at information on the subject with no real agenda. Following this pattern with respect to ULF I began once again to think of servo bass. Basically, I wonder if it has improved in terms of musical utility since the early Velodyne (etc.) "one-note" systems that were also impossible to integrate into a system.
These days, some of the servo systems come with user-adjustable bias and narrow enough ranges of adjustments to where it appears it might actually be useful. Sure, pure output is nice, but there is simply no getting away from the room and the rest of the system in the case of (U)LF, so it appears that any "universal" approach must include provisions for careful individual tailoring along with "enough" pure power to get the rote part of the job done. Distortion under these circumstances can be very high, practically speaking, and certain servo approaches at least appear to offer a chance to effectively lower ultimate power requirements and working distortion, both, via the same trick of putting the speaker itself in the feedback loop. So, now I wonder.
While a decent 40 Hz may be more difficult than many people realize, significant quality output at 20 Hz is another thing, altogether. How best to approach the mysterious "bottom octave" of music?
Rather than close now, when I should, I will take full advantage of the initial set-up by turning readers on to the strange and wild "scientist", Royal Rife; and I am always pleased to repeat the name of Rupert Sheldrake to any Students of Life who do not already know of him.
Best regards,
Paul S
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Posted by Vasyachkin on
07-18-2010
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fiogf49gjkf0d I don't see the problem with getting 20 hz bass.
You have to keep in mind that the average signal levels at 20 hz in MUSIC are quite low ( compared to signal levels @ 40hz - 80hz ).
When i ran a quiet sinewave sweep on my system it seemed the driver will pop out of the basket at 20 hz, but when i played music MUCH LOUDER than the sinewave sweep the driver was fine.
You have to think about the musical instruments that you're reproducing. Let's say you're reproducing a kick drum that displaces a finite volume of air during a kick - then your woofer only need to be able to displace AS MUCH air on the stroke even if there is a 0.0001 hz component to the kick sound.This way it essentially boils down to having a system slightly larger ( in terms of cubic feet ) than the instruments it must reproduce.
I mean if you look at a speaker like Genelec 1036A driver-wise it has the same kind of drivers as are used in systems that roll off at 40 hz. But instead it rolls off at 20 hz - and it is simply because they tuned it for Studio rather than dance club use. They did however go with substantial cabinet volume.But when i said i like a lot of bass i didn't mean that i like the system to reach to 20 hz ( which i do like too ) but rather that i like when there is more bass at ALL frequencies.
Here is the frequency response of the earbuds i am using when i jog:
graphCompare.php
It comes pretty close to my idea of proper bass. Oh and by the way i use "deep" EQ preset on my iPhone with them. Of course aerobic type activities seem to call for ( much ) stronger bass than sitting back in a chair just listening. Also depends on the mood - sometimes too much bass makes me tired, at other times i can't have enough.
The problem with Servo as i see it is that accelerometers aren't designed for music. Theoretically it makes a lot of sense to use servo ( accelerometer ) bass, but in practice you are at the mercy of that piece of silicon. I am sure accelerometers could be developed to the level where they would be musical but i don't think anybody is working on that.
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Posted by Paul S on
07-18-2010
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fiogf49gjkf0d Your point about relative levels is well taken. Still, the typical concert grand piano, for instance, does about a 27 Hz fundamental, as I recall (and certain pianos go rather lower), and some other instruments are not far behind. If to simply low pass/pad down to <20 Hz with drivers that will take the heat, we are probably looking at a fairly serious power requirement and fairly serious distortion. But I suppose the notion of power - like everything else - is relative. A friend recently corrected my "memory" of an 8 X 515s per side stereo LF array when he told me the drivers were actually 15" McCauley units with a total of 4,000 Watts on tap; and then he told me that this "isn't much" by today's standard, and "they don't go that low".
So, I guess it's all what you're used to.
I do not know and so could not even guess if the "silicon" or the driver itself would be the weaker link in producing ULF these days. So I am fishing to see what any readers know about ULF in general and "contemporary" servo ULF in particular. If the accelerometer is not designed for music, what, if not a feedback loop, controls the long stroke of a ULF driver powered with a big AB amp or, more likely, a D or H amp? Isn't this in the end mostly a less-efficient way of attempting the same thing, ie, "control" of the woofer via its motor?
Best regards,
Paul S
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Posted by Vasyachkin on
07-19-2010
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fiogf49gjkf0d  Paul S wrote: | | the typical concert grand piano, for instance, does about a 27 Hz fundamental, as I recall (and certain pianos go rather lower), and some other instruments are not far behind. |
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all of the acoustical energy generated at that 27 hz comes from a single finger of the pianist. the best athletes can generate a peak power of 1 kilowatt with their legs so you can estimate the power of 1 finger. also you have to consider that the radiating area of a string is only a few square inches, virtually all of the output is cancelled with the out of phase back wave and the frame to which the strings are mounted is orders of magnitude heavier than a speaker cone. in other words there is simply no issue reproducing that 27 Hz note.
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Posted by Vasyachkin on
07-19-2010
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fiogf49gjkf0d | Paul S wrote: | | I do not know and so could not even guess if the "silicon" or the driver itself would be the weaker link in producing ULF these days. So I am fishing to see what any readers know about ULF in general and "contemporary" servo ULF in particular. If the accelerometer is not designed for music, what, if not a feedback loop, controls the long stroke of a ULF driver powered with a big AB amp or, more likely, a D or H amp? Isn't this in the end mostly a less-efficient way of attempting the same thing, ie, "control" of the woofer via its motor? |
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there isn't necessarily a need to control anything electrically here. control with respect to subwoofers refers to control of box resonance which can be accomplished mechanically with a resistive box vent.
it is possible to also have amplifiers without negative feedback you know. as a matter of fact i invented one such amplifier but years later learned that it had already been implemented. an amplifier using a transformer as a voltage gain element is inherently linear and requires no correction.
negative feedback is only needed to correct errors. but it is possible to design a system without errors in the first place. TC Sounds LMS subwoofer for the most part is such a driver - its error without any accelerometers is at about the same 2% as for Velodyne WITH accelerometer.
question is - what sounds worse - 2% distortion from a driver or 2% distortion from an accelerometer ? accelerometer is essentially a piezo tweeter wired in reverse, so Velodyne is essentially a piezo subwoofer LOL.
well, actually there can be different accelerometer technologies - it can be capacitive as well, but even so the "suspension" is still made out of silicon and crystals aren't known for being very linear when it comes to deformation.
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Posted by Vasyachkin on
07-19-2010
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fiogf49gjkf0d I suggest we end this conversation before i am asked to leave again
There are physics forums you know Paul, like this one:
http://www.physicsforums.com/
They will be happy to answer your questions there.
It was a very clever Troll on your part to take my science bashing thread and turn it into a science fair
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Posted by Paul S on
07-19-2010
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fiogf49gjkf0d It is almost ironic, in the context of your original post, that you've refered me to "Physics" as a sort of generic introduction or prerequisite to practical musical ULF. But I do appreciate your applied thoughts on the evils of feedback loops, and the driver tip; and mea culpa, the twist in your thread.
I suppose you are kidding about being "asked to leave" (again). In case you are wholly or partly serious, while it is indeed easy to draw fire here, it is generally only the most determined idiots that get bounced. In fact, I've begun to think there is a sort of "Audio Adventure Tourist Club" composed of people who somehow accrue points with their kin if they manage to get run from here. If GSC is not Everest for these clowns, perhaps it is Anapurna. Anyway, as you can see, nothing said so far has drawn much interest, let alone censure.
FWIW, I did not realize until now that you took your science post so seriously.
I'll eventually start a proper thread on the practical matters of bass, and when I do, in the spirit of fair play, you are welcome to respond OT.
FYI, I actually tried to look at the website you are trying to boost here, but my protective browser (Explorer + Romanian anti-virus) refuses to open the page. Are you "trolling" (or phishing), yourself?
Best regards,
Paul S
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Posted by noviygera on
07-20-2010
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fiogf49gjkf0d | Paul S wrote: | Your point about relative levels is well taken. Still, the typical concert grand piano, for instance, does about a 27 Hz fundamental, as I recall (and certain pianos go rather lower), and some other instruments are not far behind. If to simply low pass/pad down to <20 Hz with drivers that will take the heat, we are probably looking at a fairly serious power requirement and fairly serious distortion. But I suppose the notion of power - like everything else - is relative. A friend recently corrected my "memory" of an 8 X 515s per side stereo LF array when he told me the drivers were actually 15" McCauley units with a total of 4,000 Watts on tap; and then he told me that this "isn't much" by today's standard, and "they don't go that low".
So, I guess it's all what you're used to.
I do not know and so could not even guess if the "silicon" or the driver itself would be the weaker link in producing ULF these days. So I am fishing to see what any readers know about ULF in general and "contemporary" servo ULF in particular. If the accelerometer is not designed for music, what, if not a feedback loop, controls the long stroke of a ULF driver powered with a big AB amp or, more likely, a D or H amp? Isn't this in the end mostly a less-efficient way of attempting the same thing, ie, "control" of the woofer via its motor?
Best regards,
Paul S |
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Quote: "This article offers concepts and techniques for getting good bass. Our focus will be the frequency range from approximately 20 Hz to 150 Hz"
http://www.prosoundweb.com/article/a_practical_guide_to_good_bass_part_1_acoustical_concepts_of_subwoofers/
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Posted by Vasyachkin on
07-21-2010
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fiogf49gjkf0d | Paul S wrote: | FYI, I actually tried to look at the website you are trying to boost here, but my protective browser (Explorer + Romanian anti-virus) refuses to open the page. Are you "trolling" (or phishing), yourself?
Best regards,
Paul S |
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My website is down. I don't know when i will get around to fixing it.
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Posted by Vasyachkin on
07-21-2010
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fiogf49gjkf0d | noviygera wrote: | |
be careful applying the information in this article to home audio. bass in a room is very different from bass in a large venue.
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Posted by Vasyachkin on
07-21-2010
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fiogf49gjkf0d | Paul S wrote: | | But I do appreciate your applied thoughts on the evils of feedback loops. |
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I don't think that feedback loops are evil. They solve some problems and create others.
Your human body employs a virtually infinite number of such loops as part of its design - and the human body is by far the most advanced work of engineering. In fact the very engineering process that gave birth to it - evolution - is itself a negative feedback loop.
evolution however is based on trial and error and REAL-LIFE performance. Evolution doesn't care about arbitrary parameters like %THD - it cares about WHAT WORKS BEST, it cares about the END RESULT.
Generally speaking the more advanced a system ( not talking about audio systems here ) is the more negative feedback loops it will have. But also the more advanced a system the more it is also likely to be a failure. Some of the simplest systems like a nail in mechanical engineering or a virus in biology - are some of the most successful ones. And some of the most complex systems - like communism - are some of the biggest disasters.
the problem with feedback loops is that they usually increase complexity. but not always. for example capitalism is based on feedback loops and is simpler than communism - and it works better.
a feedback loop is a very powerful tool - and like most powerful tools it can be used for good or for evil.
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Posted by Paul S on
07-21-2010
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fiogf49gjkf0d
From the thoughtful, absorbed tone of your posts, at this point in your self-education/personal feedback cycle, you might enjoy a book entitled, "Consilience; The Unity of Knowledge", by Edward O. Wilson.
Then, in light of this, you might enjoy reviewing Levi-Strauss, Derrida, etc., to look again into how we cook up the version of reality that suits us.
In case you wonder, at this time in my life, I think "Capitalism" has not solved the problems of "Communism", since criminals (like cockroaches) are where you find them; but this is hardly the forum to get into it.
Best regards,
Paul S
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