The Korf Blog

The inside story: our research, development and opinions

12 September 2017
Prototype 5, No Surprises
Prototype number 5 has a 10 mm diameter brushed stainless steel armtube with 0.5 mm wall thickness.

In my opinion, this is the best-looking armtube so far. It looks and feels solid.

Below is the vibrometry chart. I've left the Prototype 3 and Prototype 4 on the chart for comparison.
And almost everything is entirely predictable. The very stiff steel tube doesn't really flex much. It has a bit more material, so its damping capacity should be a bit better — and yes, the measured 800 Hz main counterweight resonance is a bit lower.

The only surprise is the second harmonic of the counterweight resonance that shot right up. I think it is a function of counterweight position. Moving it back and forward even a bit drastically changes the harmonics. It isn't a very well designed counterweight, but we'll have to live with it for the time being.

Subjective evaluation
Not much to say here compared to Prototype 4. Still good, nothing's been ruined. Feels a tiny bit better, but it's entirely possible that the improvement comes from a better cartridge matching. The cartridge compliance resonance of Prototype 5 is desirable 10 Hz, while Prototype 4 has a bit marginal 7 Hz.

Result: ★★★★
Next week, next arm tube!
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