Speaker spec terminology, what do these mean?

[sparkless]

Can anyone explain what these speaker spec terms mean?
Have looked on the net & books but to no avail.

Krm= in m Ohm
Erm=

Kxm= in m H
Exm=

Thanks for any help

Steve

 

[PeteMcK]

http://pagesperso-orange.fr/francis.audio2/VoiceCoilIpedance.doc

 

[sparkless]

Thanks for that info Pete.

I have those specs for a speaker, but not Le, so I'm using the Le = Kxm x @ to the power of (Exm - 1) formula.

This part is confusing me;

>>where @ = 2 x pye x f; { f = frequency in Hz }

What frequency? Where do I get that figure?

Thanks for any help.

 

[bjorno]

This part is confusing me; >>where @ = 2 x pye x f; { f = frequency in Hz } What frequency? Where do I get that figure?

Hi sparkless,

Maybe this could be of help? Picture 1(1) :

b

1(1)

 

[AndrewT]

in those formulae, is x = multiplier? = *

kxm x w = K * M * w ???? (w= greek omega)

and Exm -1 = E * M^-1 = E/M??

otherwise, I am lost as well.

 

[AndrewT]

Pi = greek symbol for 3.14159 = Circumference / Diameter.

 

[bjorno]

n those formulae, is x = multiplier? = *

Hi Andrew,

Yes but not in Exm or Kxm where x indicates a reactive element.

I admit that using x as a multiplicative operator can confuse.

Here's a better picture:

b

1(1)

 

[sparkless]

Thanks Bjorno for that info.

>>Omega, f, are not constant but variable<<

Understood. What I am not sure about is , when the specification
Le is given for a particular woofer at what F is that figure based on?
I believe it is usually 1K, is that correct? (need this spec for Zobel)

Steve.

 

[bjorno]

Understood. What I am not sure about is , when the specification Le is given for a particular woofer at what F is that figure based on? I believe it is usually 1K, is that correct? (need this spec for Zobel)

Hi Steve,

Correct! The primary standard measurement point is at 1 k Hz.

b

 

[sparkless]

>>Correct! The primary standard measurement point is at 1 k Hz<<

thanks bjorno
So if I'm using a Zobel for a woofer that's to be crossed over at 2500Hz should f = 2500 to get the correct Le ?

C = Le/Rc2 Rc = 1.25 Re

 

[bjorno]

..So if I'm using a Zobel for a woofer that's to be crossed over at 2500Hz should f = 2500 to get the correct Le ?..

No, Le should be measured at 1 kHz because thats the frequency point where the Zobel network is supposed to correct the driver impedance.
See my picture 1(1).

b

1(1)

 

[sparkless]

Le should be measured at 1 kHz because thats the frequency point where the Zobel network is supposed to correct the driver impedance.

Thanks for clearing that up bjorno, much appreciated.