Glasswolf, or anyone else with extensive magnetism knowledge..

 

Silver Member
Username: Skies

Courtenay, British Colu... Canada

Post Number: 446
Registered: Aug-05
Glasswolf,
I'm taking physics and a few questions arose which I forgot to ask my teacher... Why is a "watt" used instead of just amperes, since that is what makes the electromagnet work?

Also, are permanent magnets(e.g. subwoofer motor) measured in tesslas too ?

And now... Why does it take more power to get a DD 9917 moving than a simple infinity reference sub? The motor on the DD is bigger, therefor it would take less power through the VC to repel from the motor would it not?

Thanks
 

Silver Member
Username: Jonesp

Post Number: 204
Registered: Sep-05
for one thing i no amps will kill you rather than watts
 

Silver Member
Username: Jonesp

Post Number: 205
Registered: Sep-05
for one thing i no amps will kill you rather than watts yea i know it has nothin to do with you question
 

Silver Member
Username: Jonesp

Post Number: 206
Registered: Sep-05
for one thing i no amps will kill you rather than watts yea i know it has nothin to do with you question
 

Gold Member
Username: Southernrebel

Monroe, Louisiana DD 9515d~~]...

Post Number: 4749
Registered: Mar-04
Watt = 1 Joule/sec/sec
Its a measure of HEAT.

The reason it takes more energy to more a DD sub is due to the suspension. DD=stiffer, but more controllable.
 

Silver Member
Username: Skies

Courtenay, British Colu... Canada

Post Number: 450
Registered: Aug-05
Okay, but heat isn't what makes an electromagnet is it ? Electromagnets will still work at -50ºC, will they not?

Okay that makes sense... Also, I assume the mass of the cone would affect it too then...

Now, people say after their subs are "broken in" the suspension becomes much softer... Would this also mean it takes less power to reach same loudness(in theory)?
 

Silver Member
Username: Hgihkcin

Lincoln, NE

Post Number: 121
Registered: Sep-05
no heat isn't what makes it a electromagnet, i think canaan meant a measure of energy(energy=heat), heat is just the wasted energy, yes the mass of the cone would affect it too, but not noticeably, almost all sub woofer cones are built to be extreamly light weight. if they decided to make the cones out of some sort of heavy metal then it might have an effect, and your last question I'm not sure about but i would they that would happen, but again the effects would be minuscule
 

Silver Member
Username: Riskyb

Post Number: 528
Registered: Feb-06
"Watt = 1 Joule/sec/sec
Its a measure of HEAT.

The reason it takes more energy to more a DD sub is due to the suspension. DD=stiffer, but more controllable."

Canaan is right but not entirely. A watt is just equal to what you said. A watt is equal to that much energy over time. A joule is time independent. They had to come up with a unit for energy over time and they called it the watt.

A watt is a measure of power. The formula for power is

Power = Work/Time

I'm a little confused by your question:
"Why is a "watt" used instead of just amperes, since that is what makes the electromagnet work?"

The watt isn't really used to find the strength of an electromagnet. The formula for the force that an electromagnet creates is

Force of magnet (In newtons) = B(The tesla of a magnet) X I(the current in Amperes) X L (The length of wire in meters)

Next, "Also, are permanent magnets(e.g. subwoofer motor) measured in tesslas too ?"

Yes all magnets can be measured in tesla. Tesla is the SI unit of measurement of a magnets density with in it's field.

Finally "And now... Why does it take more power to get a DD 9917 moving than a simple infinity reference sub? The motor on the DD is bigger, therefor it would take less power through the VC to repel from the motor would it not?"

Yes it would take less power theoretically. The longer the voice coil the stronger the electromagnet.

There are many other factors to consider such as the weight of the cone etc. Providing manufacturers don't lie, you can see a sub's efficiency rated as how many decibels it achieves at 1 meter. This would be your best bet for seeing a sub's efficiency because it takes into account all the variables of the speaker.
 

Silver Member
Username: Skies

Courtenay, British Colu... Canada

Post Number: 462
Registered: Aug-05
I'm a little confused by your question:
"Why is a "watt" used instead of just amperes, since that is what makes the electromagnet work?"

The watt isn't really used to find the strength of an electromagnet. The formula for the force that an electromagnet creates is

Force of magnet (In newtons) = B(The tesla of a magnet) X I(the current in Amperes) X L (The length of wire in meters) "



I meant, because the formula for "B" is
B = ((Mew'not')(N)(I)) / L

I guess, because Watts = VI, and V is somewhat constant, the more the watts go up the more current flows.

Efficiency, labelled as "SPL" by most manufacturers is a form of measuring efficiency then?

How would the magnet weight convert into Tessla ?
 

Silver Member
Username: Riskyb

Post Number: 531
Registered: Feb-06
"I guess, because Watts = VI, and V is somewhat constant, the more the watts go up the more current flows"

Exactly.

"Efficiency, labelled as "SPL" by most manufacturers is a form of measuring efficiency then?"

Yes. Manufacturers lie but, supposing they didn't what you could do to get a woofer's efficiency is give it 1 watt and measure the SPL at 1 meter. The woofers with higher SPL ratings at 1 watt per meter would be more efficient because it takes the same amount of power to get more output.

"How would the magnet weight convert into Tessla ?"

It doesn't really. Tesla can be measured with magnetometer, I believe.

The only way to compare weight to the strength of a magnet would be if you had magnets all of the same substance. Like all iron-ferrite or all neodymium.

You can't just say "oh this iron-ferrite magnet is 5 lbs so it's stronger than this neodymium magnet that is only 3 lbs". This is because neodymium magnets are known to have more tesla per weight than iron-ferrite magnets.
 

Platinum Member
Username: Glasswolf

Wisteria, Lane USA

Post Number: 11751
Registered: Dec-03
just saw this, but guess it's already taken care of.
« Previous Thread Next Thread »

Add Your Message Here

Bold text Italics Create a hyperlink Insert a clipart image Add a YouTube Video
Need to Register?
Forgot Password?
Enable HTML code in message
   



Main Forums

Today's Posts

Forum Help

Follow Us