just trying to further my knowledge in the makings of a subwoofer...or any driver for that matter after telling my wife that i would be spending a weekend with what i thought were some of the most knowledgable people I know in the industry, she had but one question for them. "How does the sub produce 2-3 different bass notes at different frequencies at the same time?" i stopped and thought....i really don't think i know the correct answer...so instead of waiting a month...i decided to ask here how does the sub produce 2 different freqs at the same time...such as a a low constant 30hz rumble while also accurately reproducing 40-50hz bass notes at the same time? please...the full unedited unadultrated reply :?:
Kinda makes you think heh? Maybe i dont know as much as i thought i did. I cant begin to answer that question. Funny how we put so much time into learning and mastering this sport but lil things like this sends us into scratching our heads without a clue. I'll bet geo will give us a pretty good understanding. :yes: :huh:
the frequencies add you know how a sine wave looks? add the 30Hz wave to the 40Hz wave and see what you get... Side note: Your ears are able to distinguish the different frequencies based on where the hairs in your inner ear are vibrating... Different sections of hair in the inner ear vibrate with different frequencies... and your brain is able to interpret it as different frequencies Also, it's much easier to tell the difference between 40Hz and 50Hz than 10000Hz and 10010Hz.... edit: here's a simple plot of the two frequencies over a time period of 0.2seconds. you simply add the value of the blue curve to the value of the green curve at the same time and you get the bottom curve. So take a look at the values of the two curves at each of the squares (blue and red). Add those two values up, and you get the value below in the black square. The bottom curve doesn't look so nice like a sine wave, but you can see it repeats after 0.1 seconds. That's because the difference between the two frequencies is 10Hz and 1/f = time, so 1/10Hz = 0.1s. This bottom curve represents the motion of your speaker cone, and in effect, the signal that you're receiving at your ears. It's actually the two tones being played together, but it's only output as ONE signal by the speaker. Your brain has something like a filter in it, to let you interpret that this is actually two tones being output by the speaker.
I'm tired and it's late, but I've been through a discussion of this before. It concerned with how an amplifier receives a signal and then distributes the power. I've taken the best stuff and posted it here. Here is the link: (long interesting read) http://www.hometheaterforum.com/htforum/sh...387#post1723387 I'm Brian Tatnall http://www.eatel.net/~amptech/elecdisc/frequncy.htm One of the examples shows multiple frequencies and more specfically gives the example of two sine waves like you are suggesting: Remember that your speaker is only playing one frequency at a time really. Basically has one amplitude at any point is what I mean. It combines the different since waves into one combination wave looking like this: This is what your amp and speaker actually see. It takes the brain to divide up the wave and recognize the two sine waves being played at the same time. When looking at the combined wave in terms of power it just takes the amount of power for the single combined wave. So what does this mean when combining waves? Just like in a pool when waves collide they create crests and valleys. Sound does the same thing!!! When you combine waves some parts are amplified even more and some parts have a decrease in amplification. Like in the picture I showed of the two sine waves combined. Your amp and speaker do not see each sound individually. They see one amplitude at any point in time. ONLY ONE. If you feed an amp or speaker two then it will create ONE anyway. ONE and ONLY ONE. About sinewaves, If all waves were seperatly amplified and amplifaction doubled for every sinewave played at the same time how would the subs cone move. would it play every wave seperatley at the same time? would it move say 20 cycles/second and then 30cycles/second at the same time. How could it? Would we here both tones or a combination of the two.
wow...still reading the links...but i see that it is how my brain percieves it...not actually a function of the speaker i'll go back to reading now
see your all wrong When a Sound a Played, the matrix sends a Electic Signal to the big metal rod shoved in to your brain
It's called superposition... The graphs above are great explanations of what happens. You don't hear each frequency on its own, you hear the sum of the frequencies. Note that IMD is when you add the two frequencies together in a nonlinear way and get extra frequencies (like adding 70 Hz and 90 Hz, and getting some 110 Hz (90 + (90-70)) mixed in). Dan Wiggins Adire Audio
These plots are great illustrations of what happens. When you combine multiple frequencies, you get complex waveforms like these. This is the signal that your speaker is going to be fed, and this is the signal that it is going to try to replicate... not two separate waveforms at once...although that's technically what this summation actually is. In terms of voltage, look at that plot. The X axis represents "time". The Y axis in the scope of a signal would then represent "voltage". Remember, this signal is AC electricity... but unlike the voltage in your home, whose frequency is always 60hz, and amplitude is always 120v, music is more dynamic.. the frequency is most often a complex waveform of varying frequency(or frequencies), and amplitude is variable depending on the recording level of the signal in the music, and your hand on the volume knob. So... the red line represents 0v, positive voltage (or rather, voltage in one direction) above the red line, and negative voltage (or rather, voltage in the opposite direction). Pretty simple. So what happens when you feed this signal into a speaker? It turns it into cone motion, or excursion... and it mimics the amplitude of the signal fed into it. So... In terms of excursion, look at that plot. The X-axis still represents "time". Now, the Y-axis could represent "excursion". The red line would represent the speaker's "at rest" position... or 0mm of excursion. The area above the red line represents positive excursion, the cone moving out of the basket... (if the sub is not wired backwards, anyway And the area below the red line represents negative excursion. Thinking about it this way, you can easily see exactly what the subwoofer is doing with the signal, and where the signal ends up "putting" the cone at any given moment in time, as that signal is fed into the speaker. Make sense? :detective:
If you read the thread that I linked to over on HTF you'll find that you need more power for each frequency you add. More frequencies = more amplitude so don't forget to buy enough power for every sub!!!
