Can't figure out how to read this impedance graph

[Bmsluite]

Silver Flute W17RC38-04
I have never seen an impendence graph like this.
How do I read this? I am trying to trace it to see if its a viable choice for a build I am considering. Basically a budget 2 way build I could give away to friends.
How does the "V" translate to ohms?​

 

[Ugg10]

My first guess is that the right hand side axis is incorrectly labelled and the gradations should be 10, 20, 30, 40 ohms. Only a guess but would make the minimum impedance around 8ohms and the resonance peak about 35ohms which seems plausible.

 

[AllenB]

I'd expect to have to measure it again.

 

[Dave Bullet]

https://ampslab-spk.com/2018/05/19/silver-flute-w17rc38-08/

 

[eriksquires]

Based on Re of 3.7, id say treat the right axis as milliohms the multiply by 100.

 

[Bmsluite]

I'd expect to have to measure it again.

This is the factory graph. I've never seen one like this though

 

[adason]

Fs is 42Hz, impedance is 7.2 ohm. According to this blue impedance sweep.

 

[AllenB]

I've never seen one like this though

Nor should you. It's not unusual to measure impedance as Volts, but not to display it that way.

 

[mbrennwa]

How does the "V" translate to ohms?

It does not. The plot title indicates impedance, but there is no impedance on any of the x-axes.

All I can tell is that there must be an error. If this really is a plot by the manufacturer, they don't seem very competent at what they do.

 

[Ugg10]

I quickly overlaid the spec sheet and Ampslabs data and they line up for100mV = 10ohms which seem to confirm it is a mislabeling of the graph. Even the wiggle at 1khz is seen on both and lines up. Peak at FS is lower but this is likely due to the baffle they were both tested on.

 

[torgeirs]

Silver Flute W17RC38-04​

How does the "V" translate to ohms?​

Is it just R = U/I? So they have used a constant I for the sweep and measured the U in volts across the speaker terminals?

 

[Bmsluite]

My first guess is that the right hand side axis is incorrectly labelled and the gradations should be 10, 20, 30, 40 ohms. Only a guess but would make the minimum impedance around 8ohms and the resonance peak about 35ohms which seems plausible.

That seems reasonable. I will just use that I guess

 

[Bmsluite]

View attachment 1344033

I quickly overlaid the spec sheet and Ampslabs data and they line up for100mV = 10ohms which seem to confirm it is a mislabeling of the graph. Even the wiggle at 1khz is seen on both and lines up. Peak at FS is lower but this is likely due to the baffle they were both tested on.

Thanks for this

 

[torgeirs]

So maybe a 10 mA constant current source then. 10 mA x 10 ohm = 100 mV