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Why so much bass?


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Steven Kephart 
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Posted: March 11, 2005 at 11:47 AM / IP Logged  

And you still haven't answered my question.  What is this "force" measured in?  My guess by your description is dB.  However your definition of frequency is wrong because when you change the output (higher/lower dB)  you do not change the frequency. 

Steven Kephart

Adire Audio

Poormanq45 
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Posted: March 11, 2005 at 7:04 PM / IP Logged  
alien wrote:
A cycle is the force you are making per instance of time. If there were no forces acting then time would not matter and therefore freqeuncy wouldn't matter. High freqeuncy tuned sounds therefore have more instances where the amplitude of the sounds are changed.
Incorrect on pont A and point B.
About the high frequency changing amplitude, this is just totally bullsh*t. You can play a constant test frequency of 15k Hz at 120db from a tweeter and a constant test frequency of 20Hz at 120db from a subwoofer. So now tell me, if the frequency remains the same, and the electrical AND acoustical power remain the same, where are you saying that the amplitude is changing? It's notWhy so much bass? - Page 6 -- posted image.
alien wrote:
At 120hz the driver will be accelerated forward and back at a rate of 120 times per second. The changes the ear drum experience must be equivilant.
OK, if you're so smart, then why don't you calculate the actual acceleration if the driver were moving, oh lets say 2in peak to peak.
And no, the ear drums will not always be affected at the same frequency that the driver is producing. The surrounding environment can alter the frequency that is actually heard compared to that of which is being produced.
sedate 
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Posted: March 12, 2005 at 2:49 AM / IP Logged  
Alien, screw these clowns, I think ur onto something.
You're just not expressing it very well.
This whole started, before everyone jumped all over Alien, because he made the observation that higher frequencies were more damaging to hearing than lower frequencies, given the same SPL. This is, from my own experience, correct. EVERYONE in here will have to admit that 140 dB ripping off of a pair of Infinity EMIT tweeters will be TORTUROUSLY PAINFUL while 140 dB pounding off two Perfect12's would be a MASSAGE.
Now, because I have a feeling Alien is on the right track, if a bit vague..
Steven Kephart:
Alien is not wrong about his definition of frequency, just muddled. Please believe me, frequency is the number of vibrations or oscillations in units per second, measured in cycles or Hertz per second. The rate of repetition in cycles per second (Hertz) of musical pitch as well as of electrical signals. For example, the number of waves per second a vibrating device such as a piano or violin string moves back and forth each second of time to produce a musical tone. Frequency or Cycles or Hertz = Motion/Time. The "Force" he is talking about is motion, since, physically speaking, they are both one and the same. Force = Mass*Accerlation. You would agree that something that has mass and is accerlating is "in motion," wouldn't you?
Poormanq45:
I *LOVE* math!
When you state that Alien is "Incorrect on pont A and point B." not only are you making an egregious typo, but you are actually, totally incorrect yourself. Alien CORRECTLY asserts that if there is no force, everything else is irrelevant. Alien is MATHEMATICALLY CORRECT; when you place a zero for Motion where Frequency = Motion/Time, the rest of the equation becomes.. thats right! null and void and equal to zero.
Alien is not saying the amplitude is dynamic (changes at the same frequency) just that when you look at a frequency response curve of a higher frequency, there are alot more "waves" for a given period of time over a low frequency ... the wavelength is shorter. (...and Alien's English is real muddled..)
Oh, even though you already know this I'm sure, you don't provide enough information to answer the "acceleration" of a driver, since Accleration = DeltaVelocity/DeltaTime.
Or, the Change in Velocity/Change in Time. But, you actually low ball the velocity itself. At 120 Hz and 2-inches peak-peak you would get about 240 inches/second, or about 13.5 mph.
DYOhn:
I read, with utter facination, your thought exercise a few days back about the peak-excursion behavior of a driver while playing a flat, distorted wave and the resulting affect on heat dissapation within the driver.
How can you go from providing such an outstanding explanation like that to telling Alien he's pushing a load of misinformation and then leaving it at that? Then saying that he's misapplying physics and such.. you know, you always explain yourself real well.... how about this time? How is he "mixing up basic principles of physics?" To be blunt, loudspeaker operation is an excercise in basic physics. Alien is posting equations and citing specific physical laws.. you're just telling him he's wrong and mixed up. Again, as specifically as you can muster (I can take the techno-talk), how so?
Alien:
OKAY I think I know what you are trying to say but not managing to, at all:
Higher Frequencies have MORE power than lower frequencies because they MATHEMATICALLY have to. Higher Frequencies have a SHORTER wavelength, resulting in MORE motion over the same period of time. By the MATHEMATICAL DEFINITION OF FREQUENCY when you hold TIME constant, and INCREASE power, THE FREQUENCY MUST INCREASE.
Is that why higher frequencies hurt hearing more than lower frequencies holding constant for volume? They inherently must contain more power for dB level?
Steven Kephart 
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Posted: March 12, 2005 at 3:28 AM / IP Logged  

sedate wrote:
Steven Kephart:
Alien is not wrong about his definition of frequency, just muddled. Please believe me, frequency is the number of vibrations or oscillations in units per second, measured in cycles or Hertz per second. The rate of repetition in cycles per second (Hertz) of musical pitch as well as of electrical signals. For example, the number of waves per second a vibrating device such as a piano or violin string moves back and forth each second of time to produce a musical tone. Frequency or Cycles or Hertz = Motion/Time. The "Force" he is talking about is motion, since, physically speaking, they are both one and the same. Force = Mass*Accerlation. You would agree that something that has mass and is accerlating is "in motion," wouldn't you? 

Speakers are a constant acceleration device.  So if acceleration is constant, and mass is obviously constant, force MUST be constant.  Force does not change with frequency.  You are correct that some higher frequencies do hurt our ears more than lower frequencies.  But this is because our ears are more sensative to these frequencies.  Our ears are most sensative to IIRC 1 kHz to 5 kHz, and the sensetivity decreases as the frequency decreases from there AND increases.  So higher frequencies actually hurt us less.  But this is a function of the ear, and has nothing to do with "extra force" of those frequencies.

sedate wrote:
Alien is not saying the amplitude is dynamic (changes at the same frequency) just that when you look at a frequency response curve of a higher frequency, there are alot more "waves" for a given period of time over a low frequency ... the wavelength is shorter. (...and Alien's English is real muddled..) 

A frequency response curve has no time reference.  It is strictly how loud the speaker is playing in the audible bandwidth.

sedate wrote:
  OKAY I think I know what you are trying to say but not managing to, at all:
Higher Frequencies have MORE power than lower frequencies because they MATHEMATICALLY have to.

Actually they mathematically can't.  90 dB at 50 Hz is the same output (same preasure) as 90 dB's at 15 kHz. 

Which is heavier; a pound of feathers or a pound of bricks?  Are you going to tell me that mathematically a pound of bricks is heavier?

sedate wrote:
 Higher Frequencies have a SHORTER wavelength, resulting in MORE motion over the same period of time.

Actually that is false.  For every halving of frequency excursion must increase by a factor of 4 to keep the same SPL level.  So in fact there is greater motion at lower frequencies than at high frequencies. 

sedate wrote:
By the MATHEMATICAL DEFINITION OF FREQUENCY when you hold TIME constant, and INCREASE power, THE FREQUENCY MUST INCREASE.

That makes absolutely no sense.  Do you mean increase cycles?  Power has absolutely no relevance to the formula.

Steven Kephart

Adire Audio

DYohn 
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Posted: March 12, 2005 at 10:17 AM / IP Logged  

This has become very tedious, but let me say one last thing since we have a new player.

Amplitude and frequency are independent factors in waves.  One does not change the other.  This is the basic physics error in the original poster's proposition.  "If you hold time constant and increase power" the decibel level increases.  Frequency will remain constant as it is dependent on other factors.  This is high school physics.

http://www.physicsclassroom.com/Class/sound/soundtoc.html

Now while frequency and amplitude are independent of one another, the vibratory energy needed to produce a sound wave is indeed frequency dependent.  As stated earlier, it is an inverse square function.  It requires far more energy and far more physical movement to generate lower frequencies than it does to generate higher frequencies at the same decibel level.  To generate a 20Hz pressure wave at any given db level requires approximately 100 times more power input as producing a 20KHz pressure wave at the same db level.  This is why woofers are large and move a lot of air and eat up gobs of power, and tweeters are small and don't move a lot and don't require as much power.  Alien's supposition implies the exact opposite.  The vibratory energy imparted by a sound wave into a physical medium is similarly inversely frequency dependent.

I'm not a doctor, but my understanding is that our ears are damaged more in the upper frequency perception ability first because the cillia inside our ears that convert the sound pressure waves into electrical impulses are much smaller than the ones that perceive lower frequencies, and are much more fragile and more easily damaged.  It is SPL, not the frequency, that damages them.  Any SPL above 85dba will cause hearing damage.

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DanWiggins 
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Posted: March 12, 2005 at 10:19 AM / IP Logged  

Hi all, A few thoughts...

SPL is Sound Pressure Level.  It is a logarithmic measure of pressure relative to 20 microPascals (20 * log(measured pressure / 0.00002)).  Inherent in that is the simple fact that pressure is pressure.  Regardless of frequency.  There is ZERO time dependency in the equation.  94 dB SPL at 1 kHz, 100 Hz, or 2 Hz is 1 Pascal of pressure.  Pure and simple.

Drivers operating above Fs are constant acceleration devices (below Fs they are constant velocity devices).  F=ma.  If acceleration is constant, and mass is constant, then force must be constant.  Simple Newtonian physics.  Note again there is ZERO time dependency in the equation, meaning that frequency is irrelevant.

The reason 115 dB SPL is "so much louder" than 125 dB SPL @ 50 Hz is the way our ears work.  Look at the Fletcher Munson (or Robinson Dadson) curves.  You'll see that our ears are much more sensitive to frequencies between 1-5 kHz than it is to frequencies below or above that range.  This isn't an indication that there is more "power" - all it means is that you hear those frequencies better, and you need less pressure to hear those tones.  Thus they "seem" louder (the Fletcher Munson curves are equal-loudness curves, that show what SPL is required for a tone to appear as loud as another tone; a 2 kHz, 0 dB SPL sounds as loud as 80 dB SPL @ 20 Hz).  This is not an indication that 90 dB SPL @ 5 kHz has more "power"; rather it shows that your ear picks up the 5 kHz signal a LOT better than the 50 Hz tone.

Dan Wiggins

Adire Audio

oonikfraleyoo 
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Posted: March 12, 2005 at 2:09 PM / IP Logged  
Man, I'm not a scientist. But I do love the way you 2 guys are making up your own laws of physics. Could you help me out with this gravity problem I'm having?
Nik
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haemphyst 
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Posted: March 12, 2005 at 3:38 PM / IP Logged  
oonikfraleyoo wrote:
Man, I'm not a scientist. But I do love the way you 2 guys are making up your own laws of physics. Could you help me out with this gravity problem I'm having?
OK, sure that might be funny - gravity problem... (a little bit), but if you are being serious about the "making up your own laws of physics", you might want to know that the man who just gave you that information is the mad scientist behind the kick-ass drivers brought to you by Adire Audio. The XBL technology included in most (if not all) of their drivers is HIS brainchild - he does not just "work there". Show some respect, man...
Making it up? I don't think so... Listen to what he has to say... learn something. That he spends his valuable time to come here and post EXCELLENT information like he has done, shows a lot about the character of the man. Dan and Steven are damn good people, and smart too! I had the pleasure of meeting them at the CES, and in the 30 minutes I was in their booth/demo room, I learned quite a bit from them both.
If you ONLY trying to be cute, please accept my apology, Nik, but I thought you might not know who you were talking to...
Thanks, Dan!
(BTW Dan, the Extremis 6.8 is a SMOKIN' driver! As if you didn't already know!) Why so much bass? - Page 6 -- posted image.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
oonikfraleyoo 
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Posted: March 12, 2005 at 3:44 PM / IP Logged  
haemphyst, I wasn't refering to Dan, Steven, DYohn, or anyone else who was making any kind of since. I was just joking though. Unless of course someone can help me fly.
Nik
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haemphyst 
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Posted: March 12, 2005 at 3:52 PM / IP Logged  
Cool, then...
I'd like to know how to fly as well...
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
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