OK,
Peak to Peak displacement = 1 cm = 0.01 m
Peak equals half... so Xp = 0.01 / 2 = 0.005 m
Frequency, f, equals 50 Hz = 50 * 2 * pi = 314.6 rad/s
The position of the cone as a function of time is:
X = Xp * sin (t * f)
The instantaneous velocity, vc, is the derivative:
vc = dx/dt = XP * f * cos(t * f)
Evaluating at t = 0, where the velocity is peak:
vc = dx/dt = 0.005 * 314.6 * cos(0) = 1.57 m/s
By P. Mouse's conservation of momentum the box and the midrange will be moving at a velocity, vb of:
vb = 1.57 m/s * 0.5% = 0.00785
Doppler shift, ds, is just a ratio thing, using 347 m/s for the speed of sound, vs:
ds = vb/vc = 0.000785/347 = 0.0000226
Finding the shift, fs, in Hz, for 1000 Hz signal:
fs = ds * 1000 = 0.0226 Hz
Seems to me that might not sound so good.
Peak to Peak displacement = 1 cm = 0.01 m
Peak equals half... so Xp = 0.01 / 2 = 0.005 m
Frequency, f, equals 50 Hz = 50 * 2 * pi = 314.6 rad/s
The position of the cone as a function of time is:
X = Xp * sin (t * f)
The instantaneous velocity, vc, is the derivative:
vc = dx/dt = XP * f * cos(t * f)
Evaluating at t = 0, where the velocity is peak:
vc = dx/dt = 0.005 * 314.6 * cos(0) = 1.57 m/s
By P. Mouse's conservation of momentum the box and the midrange will be moving at a velocity, vb of:
vb = 1.57 m/s * 0.5% = 0.00785
Doppler shift, ds, is just a ratio thing, using 347 m/s for the speed of sound, vs:
ds = vb/vc = 0.000785/347 = 0.0000226
Finding the shift, fs, in Hz, for 1000 Hz signal:
fs = ds * 1000 = 0.0226 Hz
Seems to me that might not sound so good.
Ha, I knew if I faked it long enough a real mathematician would have to get involved!
BTW, I just saw your mail.
Shin, if we allow perfect coupling between the box and the floor, this then means we have a ratio of the mass of the cone against the mass of the earth, that's a very, very small number...
BTW, I just saw your mail.
Shin, if we allow perfect coupling between the box and the floor, this then means we have a ratio of the mass of the cone against the mass of the earth, that's a very, very small number...
All of the nonsense in that article hinges on whether this is true.
Im sorry I dont see how it is, first enough sound energy has to excite the amp case into motion despite losses, then the energy has to excite the pcb into motion again there are losses, then the energy that is leftover has to distort a closed form capacitor(its fully encapsulated), it does this by flexing those weak little leads on the cap. Come on, there are way too many losses and the components are too rigid with too many attach points. So IMO, a signal cannot be generated with this vibration.
comparing lp's to cd players HELLO, the needle of a record player rides on the surface and responds to pits and bumps-aka vibrations. Cd player are digital, if it doesnt cause a skip its not an issue.
As far is ic's transistors etc. I seem to remember extremely high shock tolerances on the few components I looked at, if shocks dont disrupt function I doubt low level hums will, just a thought. hmmmmm!
"just a thought" I think this is one of the key problems with that whole site, lots of thought experiments and not much else.
yeah, opposites never attract, just take two magnets and... hmmmm wait a minute.
This whole article seems like one big conclusion, I want to read the raw or reduced data, I want to see the test procedure. I can draw my own conclusions, in fact if you have to spend pages drawing me a picture of "how it is" that's pobably not how it is.
IF any of that sutff in that article is true then there should be some data to back it up.
The data should illustrate your point, the conclusion should just paraphrase it.
Checking the website again, guess what, yep that article is marketing to help sell whatever they sell.
Anyways, thanks for posting, it has been a fun read.
ShinOBIWAN said:
"The position of the cone as a function of time is:
X = Xp * sin (t * f)"
Well, I made this mistake once before. You cannot start with position for the diff eq of a speaker. I dont feel like writing it out so let me quote eva on this one:
Assuming a piston diaphragm with uniform movement and a voice coil with negligible inductance and constant BL, driven by a sine wave, then we have a constant moving mas "M" over wich a force defined by an ondulatory function f=I*BL*sin(wt) is acting ("I" is voice coil current amplitude and "BL" is motor force factor in Newtons/Ampere).
As acceleration is just force/mass :
a = (I*BL/M) * sin (wt)
Where (I*BL/M) is a constant that does not depend on frequency, thus acceleration is not frequency dependent, it only depends on the amplitude of the input signal.
except for this part, I is a function of frequency so acceleration is too.
Finally, by integrating the previous expression across "t" we can calculate instantaneous speed, and integrating again across "t" we obtain instantaneous cone position:
v = -(1/w) * (I*BL/M) * cos (wt)
x = -(1/w^2) * (I*BL/M) * sin (wt)
Thus the amplitude of v is inversely proportional to w and the amplitude of x is inversely proportional to w^2
nunayafb, we're not computing SPL (your analysis would be correct in that case). The woofer cone's displacement and input signal frequency were givens in the problem. Poobah showed that there could indeed, under those circumstances, be measurable sidebands in the midrange.
Significant aurally? Beats me. But I do have my speakers well-anchored so they don't rock.
Significant aurally? Beats me. But I do have my speakers well-anchored so they don't rock.
Something to consider here.
Without engaging in the semantics that surrounds the doppler-phase-frequency modulation issue, a waveform is waveform after all, this can treated well enough as FM.
Now... the frequency shift is, indeed, rather small. But, there are infinite sidebands. Someguy made some rule... 98% of the energy is contained within the first 2 sets of sidebands. So that would be +/- 0.046 Hz... still no biggy as I happen to believe our ears are a bit like a spectrum analyzer.
What about the other 2%? That stuff is spread across the whole audible band, albeit mostly near the fundamental (or carrier in this case). And, that is 2% of every spectral component hitting that driver, being smeared into the noise floor.
Without engaging in the semantics that surrounds the doppler-phase-frequency modulation issue, a waveform is waveform after all, this can treated well enough as FM.
Now... the frequency shift is, indeed, rather small. But, there are infinite sidebands. Someguy made some rule... 98% of the energy is contained within the first 2 sets of sidebands. So that would be +/- 0.046 Hz... still no biggy as I happen to believe our ears are a bit like a spectrum analyzer.
What about the other 2%? That stuff is spread across the whole audible band, albeit mostly near the fundamental (or carrier in this case). And, that is 2% of every spectral component hitting that driver, being smeared into the noise floor.
I have bolted my speakers to the floor at times,and have also used guy wires bolted to the floor. I have also cut holes in the floor and done the same on the cement floor underneath.
and the active components..many times (different installs) are in different rooms. Wires run throuigh a hole in the wall. Basically, speaker wires come into the room from the remote location.
If yah want it to work, do it right.
Oh yeah, ps: I've also used adjustable damped posts to tighten/stress the top of the speaker..to the ceiling.
Or all of the above, at the same time.
I was doing such things long ago.
Imagine where I'm at now.
and the active components..many times (different installs) are in different rooms. Wires run throuigh a hole in the wall. Basically, speaker wires come into the room from the remote location.
If yah want it to work, do it right.
Oh yeah, ps: I've also used adjustable damped posts to tighten/stress the top of the speaker..to the ceiling.
Or all of the above, at the same time.
I was doing such things long ago.
Imagine where I'm at now.
While designing the Ohm Acoustics MicroWalsh speakers, over a period of several months I spent more of my time working on controlling internal and external cabinet resonances and figuring how to do so effectively in a manner suitable for production than on any other aspect of the design. We ended up using multiple types of constrained layer damping, multiple types of wood, extensive bracing, lead sheets, etc... with the specific locations nd methods of application of each being an important part of the equation.ScottG said:
No matter how romantic the notion of using "vibrant" woods like spruce, etc, may seem ~ CABINET VIBRATIONS ARE BAD, period. Unless you are some kind of uber-genious that figures out how to cause them to be in phase, that, I would like to see.
"isn't worth pursuing" HOGWASH! Hmm, does he per chance work for BOSE maybe? (There is one model of BOSE speaker I respect, one version of the 901, it was quite an interesting speaker at the time)
Hi all,
Suppose you have the most stiffer and damped pair of speakers
of the world. DIY or commercial are not important. You have the best.
Now my provocation:
If you put your hand on these speakers, you can hear they continue
to vibes.
Not only, If you check the tube-preamplifier, it vibes too.
The turntable ? the same.
When the volume is loud, you can also unplugged the right speaker
and it continue to vibes ( partial reduction only).
Now, if you are happy because You believe you have a very good
sound from your stereo system we accept and respect your opinion.
But are you sure you can't do better?
Only for this second case,
what is your "medicine"? Spikes? Wodoo?
perdone me, I have a strange sense of humor and I like jokes !
Cheers,
Inertial
Suppose you have the most stiffer and damped pair of speakers
of the world. DIY or commercial are not important. You have the best.
Now my provocation:
If you put your hand on these speakers, you can hear they continue
to vibes.
Not only, If you check the tube-preamplifier, it vibes too.
The turntable ? the same.
When the volume is loud, you can also unplugged the right speaker
and it continue to vibes ( partial reduction only).
Now, if you are happy because You believe you have a very good
sound from your stereo system we accept and respect your opinion.
But are you sure you can't do better?
Only for this second case,
what is your "medicine"? Spikes? Wodoo?
perdone me, I have a strange sense of humor and I like jokes !
Cheers,
Inertial
Though not with particular emphasis on loudspeakers - an interesting (and timely) subjective review on something as "simplistic" as "cones" and a "base":
http://www.6moons.com/audioreviews/soundmechanics/cones.html
Note that "tuning" in this instance does not mean enhancing a particular resonant character, but rather the opposite - dampening a particular resonant charcter. (..and/or possibly shifting the resonant modes to a different passband.)
This would of course have particular relevance (in a loudspeaker context) with respect to problem #2.
http://www.6moons.com/audioreviews/soundmechanics/cones.html
Note that "tuning" in this instance does not mean enhancing a particular resonant character, but rather the opposite - dampening a particular resonant charcter. (..and/or possibly shifting the resonant modes to a different passband.)
This would of course have particular relevance (in a loudspeaker context) with respect to problem #2.
If your speaker cabinet has a layer of vacuum then no sonic vibrations will pass through that at all ~ like a Thermos. Just be sure that the inner and outer barriers which contain the vacuum are connected by a soft viscous material with an extremely low Q, like sorbothane. Perhaps roofing tar filled with lead powder. Perhaps the front ring of the speaker basket should be where the speaker is suspended from, with the cabinet in mid air, many high tension cables firmly holding the speaker in place in the room all attached to the edge of the basket.inertial said:Hi all,
Suppose you have the most stiffer and damped pair of speakers
of the world. DIY or commercial are not important. You have the best.
Now my provocation:
If you put your hand on these speakers, you can hear they continue
to vibes.
Not only, If you check the tube-preamplifier, it vibes too.
The turntable ? the same.
When the volume is loud, you can also unplugged the right speaker
and it continue to vibes ( partial reduction only).
Now, if you are happy because You believe you have a very good
sound from your stereo system we accept and respect your opinion.
But are you sure you can't do better?
Only for this second case,
what is your "medicine"? Spikes? Wodoo?
perdone me, I have a strange sense of humor and I like jokes !
Cheers,
Inertial
Do you know Thermos? Speaker cabinet like a big Thermos.
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#%#................................................/
#%#..............................................[ ) <-- speaker
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#%# .............................................###
#%#..............................................#%#
#%#..............................................#%#
#%#########################%#
#%%%%%%%%%%%%%%%%%%%%%#
#############################
% = vacuum
# = airtight speaker cabinet walls ( chiuso ermeticamente? )
I only put ........... because the forum removed the spaces I had originally put and ruined my drawing.
#############################
#%%%%%%%%%%%%%%%%%%%%%#
#%#########################%#
#%# .............................................#%#
#%# .............................................#%# <-- enclosure
#%# .............................................###
#%# ..................................................)
#%# ................................................./
#%#................................................/
#%#..............................................[ ) <-- speaker
#%#................................................\
#%#..................................................\
#%#....................................................)
#%# .............................................###
#%#..............................................#%#
#%#..............................................#%#
#%#########################%#
#%%%%%%%%%%%%%%%%%%%%%#
#############################
% = vacuum
# = airtight speaker cabinet walls ( chiuso ermeticamente? )
I only put ........... because the forum removed the spaces I had originally put and ruined my drawing.
inertial said:
“Your speaker stands are pointing in the wrong direction, gentlemen”
Naturally, it does not hurt to try to eliminate the movements of the box, however minuscular they may be. But the idea to use a rigid bar pointing 90% degrees to the direction of the plane of movement, as in principle is the case with the common speaker stand??? I believe every architect or construction engineer would laugh out loudly at the idea.
To stop the speaker from moving slightly back and forth, the rigid bar would have to work in the very plane of this movement. In practice it would have to be horizontally oriented, and firmly attached to a rigid wall behind the speakers. (The ordinary stand is roughly speaking pivoted, seen from the point of view of the speaker box: The very slight movements at the top will be redused to almost nothing at the bottom And how does one stop nothing? )
People always hate me when I point this out, because they love their stands. (and of course stands look nice and stable, and they stand out as a natural place to place the speakers, so to speak). But I firmly believe that the improvement one can hear by using “optimal” stands is most easily explained in the psychological realm, same as with cables etc…
About box coloration.To reduce the typical and most noticeable box coloration, that from the vibrating panels, I personally use the lazy man’s method, which means attaching a leaden weight on the back of the bass driver itself, and in addition mounting the drive unit elastically on the baffle through rubber pieces and rubber rings/gaskets. The mechanical vibrations from the unit will thus not reach the panels of the box .These are typically vibrations in the frequency region above the actual bass, and has nothing to do with the reactive movements of the whole box, mentioned above ( which in my opinion are of little interest). The elastic mounting is a very effective mean to clean up the sound.
O.S.
Naturally, it does not hurt to try to eliminate the movements of the box, however minuscular they may be. But the idea to use a rigid bar pointing 90% degrees to the direction of the plane of movement, as in principle is the case with the common speaker stand??? I believe every architect or construction engineer would laugh out loudly at the idea.
To stop the speaker from moving slightly back and forth, the rigid bar would have to work in the very plane of this movement. In practice it would have to be horizontally oriented, and firmly attached to a rigid wall behind the speakers. (The ordinary stand is roughly speaking pivoted, seen from the point of view of the speaker box: The very slight movements at the top will be redused to almost nothing at the bottom And how does one stop nothing? )
People always hate me when I point this out, because they love their stands. (and of course stands look nice and stable, and they stand out as a natural place to place the speakers, so to speak). But I firmly believe that the improvement one can hear by using “optimal” stands is most easily explained in the psychological realm, same as with cables etc…
About box coloration.To reduce the typical and most noticeable box coloration, that from the vibrating panels, I personally use the lazy man’s method, which means attaching a leaden weight on the back of the bass driver itself, and in addition mounting the drive unit elastically on the baffle through rubber pieces and rubber rings/gaskets. The mechanical vibrations from the unit will thus not reach the panels of the box .These are typically vibrations in the frequency region above the actual bass, and has nothing to do with the reactive movements of the whole box, mentioned above ( which in my opinion are of little interest). The elastic mounting is a very effective mean to clean up the sound.
O.S.
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