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Old 4th October 2010, 09:26 PM   #7381
JoMoCo is offline JoMoCo  United States
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Originally Posted by LineSource View Post
I wonder if a Fish Speaker would sell well in the Pacific North West?
Well they even have a beer named after a mudshark. Maybe you could get the Fish Brewery to be your corporate sponsor...

Fish Brewing Company, Olympia, WA Home
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Old 5th October 2010, 12:08 AM   #7382
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Originally Posted by LineSource View Post
RAAL has also recently announced a dipole ribbon tweeter. I found this early documentation. Personally, I would minimize the baffle area by separating the ribbon's transformer off of the front mounting plate.

www.solen.ca/pdf/raal/DIPOLE140-15D.pdf

A DIY dipole ribbon tweeter is simple to construct from 0.5" x 0.5" NdFeB N50 magnets and some 0.5" square 1018 steel. I build 4" long x 0.7" wide dipole ribbons which can easily be crossed at 1,500Hz, and mount it on top of no-baffle Lambda TD15D or Tang Band W8-1808 mids. Material cost ~ $50. A no-baffle dipole ribbon tweeter has modest area required for good dispersion.

I wonder if a Fish Speaker would sell well in the Pacific North West.
the fish speaker looks like a cool project, where could i find more info about it?


Matt
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Old 5th October 2010, 01:35 AM   #7383
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Originally Posted by John Sheerin View Post
How could you leave out Toole's book? Granted Earl's book has some information on psychoacoustics, but Toole's book has tons of valuable information in it. If you don't know how your brain interprets what the speakers produce, then you have little basis for effectively applying information in any of those other books so in my world it's at the top of the list.
Wholeheartedly agreed.

Toole's book is a must read. I own both, and the complement each other nicely.

See it here on Amazon:

http://www.amazon.com/Sound-Reproduc...pr_product_top

And see Geddes' here on his website:

Home Theater

Transducers

Anand.

Last edited by nycavsr2000; 5th October 2010 at 01:41 AM.
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Old 16th October 2010, 04:17 PM   #7384
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Originally Posted by Charles Hansen View Post
OK, let's try and clarify some basic concepts here. I'm surprised that there is so much confusion, as this not rocket science.

Let's start with a table fan. It's a hot day and you want a cool breeze on your face. So you go down to the store and look at different models. They are mostly similar. They will have a motor and a fan blade and a protective grille and a base. Typically the fan blade has 4 blades.

Now some of those different fans may have plastic blades. Some may have metal blades. And of the plastic, some may be polystyrene, some may be polypropylene. And of the metal, some may be steel and some may be aluminum. If you are lucky, you might even find one with wooden blades.

But assuming the same motor and the same fan blade design, do you think that you could tell the difference between a blade made from polystyrene versus one from aluminum? In other words, you close your eyes, turn on the fan, feel the breeze on your face. Wouldn't all the materials produce the same airflow? The answer, or course, is that they will all be the same.

So now we have established the fact that it is possible to move air in such a way that the material used to move the air has no influence on the airflow.
Sorry if this is has already been pointed out.
I agree with you that a fan blade moving at constant velocity in one direction (and hence also constant force) will perform equally as well regardless of material.

But a speaker cone does not move at constant velocity, with constant direction (ie constant force).
Even a perfect sine wave of a single test tone is not constant velocity because the speaker cone is constantly changing direction, and the change of displacement with respect to time is also changing. Therefore the force applied to the speaker cone is changing (ie cyclic loading).
Obviously music is a lot more dynamic (ie the amplitude of sound waves are always changing) as well as complex (more than one frequency is heard at any one time). So the problem is significantly worse for reproducing music than it is for a simple test tone.

So this is where hysteresis becomes important. When a material is subjected to constant force (eg fan blade) the effect of hysteresis is nill.
However when you apply a cyclic load to a material, hysteresis is observed. Different materials display different amounts of hysteresis.
To keep it simple hysteresis is bad. Hysteresis means energy loss. This means distortion.

To reduce the effect of hysteresis you can either use a different material, eg metals have much lower (almost negligible) hysteresis when used in their elastic zone compared to plastics, or you can make a composite material eg various coatings, fibre reinforced materials, etc.

I am not sure how significant or audible these effects will be on a speaker cone while reproducing music, but they will be present none the less.

So now we come to the catch 22. If we reduce the hysteresis to zero the resonances which Charles talks about will be even worse because there will be no hysteresis to dampen the resonances. Resonances can be controlled by changing the geometry as well as thickness of the material, you can also apply coatings or form composite materials (eg constrained layer) but there are obviously limits to what can be done for a loudspeaker cone.
On the other hand if we chose a material which diplays high amounts of hysteresis to control the resonances, we now have bigger energy losses (ie another form of distortion).
I suppose it comes down to which is the greater evil, and trying to kill that while keeping in the back of your mind the effect of the other problem.

I don't design speaker cones, so I have not carried out these measurements to determine how significant these effects are on speaker cones.
Anyway, it is something to be aware of I suppose.

Last edited by Melon Head; 16th October 2010 at 04:20 PM.
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Old 16th October 2010, 07:52 PM   #7385
Few is offline Few  United States
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To keep it simple hysteresis is bad. Hysteresis means energy loss. This means distortion.
Why should energy loss necessarily imply distortion? An ideal resistor will exhibit energy loss (it dissipates energy associated with the electrical current in the form of heat) but it doesn't create distortion. It just reduces the current generated by a given voltage. No harmonics or intermodulation products are generated. Are you defining a non-frequency-dependent and phase-shift-free reduction in the signal as distortion?

Or are you instead arguing that hysteresis directly causes distortion but it's not because it causes energy loss?
Few
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Old 16th October 2010, 10:25 PM   #7386
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Energy loss does not necessarily imply distortion. But most energy losses are usually non-linear.
Resistors (ie non-perfect resistors) are a good example, as you apply more power across them the resistance increases. The current is not directly proportional to voltage across the resistor because the resistance actually increases as it heats up.
So the energy loss is non-linear.
Hysteresis effects of materials can be much more non-linear than this.

For a perfectly elastic material you would see a perfectly straight line between load (ie force) and displacement.
However when you apply cyclic loads to materials this is not the case, there is hysteresis.
The best example would be to compare it with a mosfet. An ideal mosfet would have a straight line of Id vs Vgs. However this is not the case. On top of that the properties of Id vs Vgs also change with changes in temperature. So when you apply a sine wave through a mosfet you get a sine wave plus some distortion. That is, it is no longer a perfect sine wave.

It is the same or at least similar with hysteresis of materials.

Last edited by Melon Head; 16th October 2010 at 10:31 PM.
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Old 16th October 2010, 10:47 PM   #7387
Few is offline Few  United States
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Thanks for the clarification of your intent. Your expanded explanation points (correctly, I think) to nonlinearity as the source of distortion rather than to energy dissipation as the source. With that in mind, would you accept "To keep it simple hysteresis is bad. Hysteresis means nonlinearity. This means distortion." as a rephrasing of your earlier statement?
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Old 16th October 2010, 11:10 PM   #7388
Defo is offline Defo  Norway
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What is this thread about really? First post isnt really that relevant anymore...

Last edited by Defo; 16th October 2010 at 11:12 PM.
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Old 16th October 2010, 11:21 PM   #7389
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Originally Posted by Few View Post
Thanks for the clarification of your intent. Your expanded explanation points (correctly, I think) to nonlinearity as the source of distortion rather than to energy dissipation as the source. With that in mind, would you accept "To keep it simple hysteresis is bad. Hysteresis means nonlinearity. This means distortion." as a rephrasing of your earlier statement?
Yes
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Old 16th October 2010, 11:40 PM   #7390
Variac is offline Variac  United States
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What is this thread about really? First post isnt really that relevant anymore...
Its about a journey.
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