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View Full Version : DCR AND OHM IMPEDANCE CONNECTION



gerard
10-18-2006, 06:02 AM
Hello

I woild like to kwow what is the connection between Dcr and impedance in a loudspeaker .

Some people have an 8 ohms impedance and a 6.3 ohm Dcr as example !

Thank you

Gerard

johnaec
10-18-2006, 06:13 AM
DCR is the actual measurement you get with an ohm meter when testing across the leads with the speaker unconnected and at rest. The "nominal" impedance is an "average" rating based over the speaker's normal operating frequencies. Points along this line may be above and below the average value.

John

gerard
10-18-2006, 07:08 AM
Thank you johanec

Does it mean if I have a 16 ohms rated speaker ( J model ) and 9.8 dcr , the speaker will be more like an 8 ohms ( H speaker ) ? Will that influence the crossover frequency ?

Gerard

johnaec
10-18-2006, 07:41 AM
You should have an impedance sweep done. That 9.8 might be the minimum point. The crossover should probably be designed for the impedance at the crossover point.

John

subwoof
10-18-2006, 08:34 AM
DCR = DC ( 0 hertz) resistance. This is what the actual resistance of the wire in the coil is. This can be all over the map and does NOT always track the impedance

Impedance = the **AC** ( measured and averaged over a range of frequencies ) "resistance" a component, network or system has.

This can go up and down depending on many factors but usually the average is specified.

In the case of the large 4" JBL coils, the DCR is around 6.2 for an *8* ohm speaker.

9.8 is right in the ballpark for a *16* ohm speaker.

sub

scott fitlin
10-18-2006, 12:53 PM
To understand better what they are saying about the impedance rising and falling proportional to frequency, when you have the ohm meter connected to the woofer, gently push the cone forward from the backside, and watch the meters display read out all kinds of crazy numbers.

Its sort of an idea of whats going on when the woofer is actually playing music. Impedance is nominal, not exact.

subwoof
10-19-2006, 05:26 PM
pushing in a cone is the same as talking into a dynamic mic. The coil moves in a magnetic gap which creates a voltage.

this has nothing to do with impedance. the ohmmeter's internal voltage is added to or subtracted from what the motor generates.

sub

scott fitlin
10-19-2006, 06:13 PM
pushing in a cone is the same as talking into a dynamic mic. The coil moves in a magnetic gap which creates a voltage.

this has nothing to do with impedance. the ohmmeter's internal voltage is added to or subtracted from what the motor generates.

subBut doesnt impedance fluctuate as the woofer plays signal? I understand that what Im saying isnt actual impedance, but it sort of gives an idea of how the impedance fluctuates with signal, motion, and frequency. I did say " sort of "!

As the woofer moves in and out to signal, the impedance doesnt fluctuate, varying with frequency?

edgewound
10-19-2006, 06:24 PM
But doesnt impedance fluctuate as the woofer plays signal? I understand that what Im saying isnt actual impedance, but it sort of gives an idea of how the impedance fluctuates with signal, motion, and frequency. I did say " sort of "!

As the woofer moves in and out to signal, the impedance doesnt fluctuate, varying with frequency?

Sure it does Scotty.

Look at any of the impedance plots in the forum and you'll see that actual impedance is dynamic.