The KOSS Electrostatic unit was still installed , so I removed
and checked resonance .
The resonance was 136 HZ. I then tested it in horn assembly
and the result was the same : 136 HZ. Appears to be rather poor throat coupling.
But it was, as I suspected (in other thread ), outside its operating range < 80 HZ.
I then tested the two 416's in free air and they were 28 HZ each. Then I tested them in the
horn - both drivers driven with signal and measured 23 HZ resonance. Better throat coupling
- better than, say, a Shearer or Mirrophonic folded stacked "W". But, like these, probably more of a
"waveguide" than true well coupled exponential loading.
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