High DCR on ribbon tweeter

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audiogurujax

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High DCR on ribbon tweeter
« on: 10 Jun 2019, 03:53 pm »
Hi, I have a technical question if anyone can answer, I was measuring the DCR of my ribbon tweeters of my GT3R GT Audio works speakers and I am confused, If I use my $30 southwire multi-meter i get a resistance of 3.7 ohms but if I use my fancy $400 BK LCR meter using DCR setting I get 19.2 ohms but if I measure the resistance (R) or Impedance (Z) at 1Khz I get 3.675ohms and  3.854 ohms respectively.

Also when I measure the DCR with the BK the ribbon tweeter moves a lot but no sound, and when measuring R or Z I can hear the 1Khz tone with the SouthWire MM It does not move or make any noise when I measure the Ohms.

Why does it moves so much with the BK measuring DCR and why is the DCR value so high on the BK?

BTW I tested the BK and is calibrated!

FullRangeMan

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Re: High DCR on ribbon tweeter
« Reply #1 on: 4 Oct 2019, 05:51 am »
Resistance (R) and Impedance (Z) are not the same thing, usually a 1kHz tone is too low for some tweeters hence the visible diaphragm motion.

HAL

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Re: High DCR on ribbon tweeter
« Reply #2 on: 4 Oct 2019, 01:14 pm »
Since the GTA ribbons are direct drive, Ohm meters use a DC current to measure the resistance.  That current flow will move the ribbon when connected. 

You would not see a 1KHz tone in the driver as moving it.  Has to be a low frequency or transient like connecting a DC voltage.  Be careful not to strech the ribbon!

I have a version of the ribbons here and I have seen what happens when they get streched.  They get rebuilt.