The Korf Blog

The inside story: our research, development and opinions

23 October 2017
Prototype 7, Constrained Layer Damping
Prototype number 7 has a ⅜ inch CLD armtube that consists of an outer 0.25mm-walled aluminium tube, a 1 mm layer of Shore A 30 silicone, and an inner tube, also with 0.25mm wall. All the layers are clearly visible on the lower photo.

Below is the vibrometry chart. I've left the Prototype 1 (same ⅜ inch aluminium armtube with 0.25mm walls, but with no damping applied) on the chart for comparison.
The results are quite surprising. I expected the constraining silicone layer to dampen the main resonance, but nothing of the sort happened. On the contrary, the Q of a dampened armtube is a lot higher compared to a simple tube!

But all the other resonances got dampened quite efficiently. In fact, this is the first armtube to affect the bearings resonance.

Subjective evaluation
Ouch. This is truly awful. This is by far the worst tonearm I've ever made. Compared to it, Prototype 1 is quite ok.

Bloated unsteady sound completely devoid of meaningful highs. I couldn't even finish listening to the first track on the album.

It looks like adding any damping to an armtube has a drastic negative effect on sound quality.

Result: ☆☆☆
Yes, zero stars.
Next week, next arm tube!
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