Why so much bass?

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

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.

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

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?

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. 

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

Steven Kephart

Adire Audio

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.

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