CLS II impedance

[lugano]

Hello folks,

Yesterday a skilled technician came to my place and we did some measurements of my CLS II's (built in february 1990). I wanted to know what's their impedance related to frequency, and he did a full plot of both channels. You can see the curve below - it might be interesting for all CLS II owners.

Some remarks:

1) The 2 ML's are practically identical in their attitude - one is plotted in red, the other in blue and the 2 curves are practically the same.

2) We measured this with 1 watt, then tried with 4 watt - no change.

3) we also measured the mean value of the sound pressure level at which I normally listen - it's 91 dB. The sound pressure level at which you feel the need to get out of the room was measured, too: 95 dB.

4) As you can see on the plot, the impedance at 1 kHz is exactly 4 ohm. Then it begins to go down, reaching 2 ohm at 5 khz and there it remains, up to 20 khz.

 

[garmtz]

I think the graph is clipping in the beginning (at the lower frequencies) and what is the vertical scale?

 

[lugano]

Yes, under 85 Hz it's over 16 ohms. We wanted to have a very precise mesurement of what happens in the higher frequencies and couldn't care less about what happens under 100 Hz, so we took the 0 to 16 ohm scale.

The vertical scale is the one on the right, checked with a red X, i.e. going from 0 to 16 ohms.

 

[IWalker]

So it really only drops down to about 2ohms? That's better than expected, no? I thought they dropped down to around 1ohm at 20k hz per spec.

 

[lugano]

So it really only drops down to about 2ohms? That's better than expected, no? I thought they dropped down to around 1ohm at 20k hz per spec.

Yes, me too. There's plenty of "these babies flirt with 0.7 ohms quite often" around. Bull. Not that a flat 2 ohms will make people and amps happy, but AFAIK CLS II's are surpassed only by CLS as being a difficult load. The IIz should be better. Good to see it. Also good was to listen to the analyzer's pattern (buuuuuooooooooooaaaaaaaaaiiiiiiiiiiiiiiiissssssssss) and realize that I kinda hear up to 16 Khz )