|Two units acquired in
2015 and 2016
Since the first two were labeled as EB-1 and EB-2, the sequence was continued. All 4 were found on ebay. These two are all original; the FS/AL surprised as the foam hasn't rotted. The adhesive holding it to the cone had to be repaired in places so it was lifted from the cone and reapplied.
The CS/AL has no wear whatsoever; it was never used. There is no evidence of screws being applied and the original solid wires, now removed but kept, were still attached to the terminals. Both have phenolic spiders and aluminum speech coils. The EB-4 unit is of a later vintage, probably mid 60's. Note the dust cap in the second photo.
The dark spot at 9 o'clock on the annulus of the speaker on the right is a drop of glue applied to seal a hole probably caused by a hungry cricket or moth.
This photo shows the phenolic spiders.
|The blue curve is that
of EB-3, the FS/AL. That's just about the only difference that can
account for the lower Fs.
The CS would make a better midrange; the stiffer annulus would slightly improve transient response.
|The red curve is EB-3, the FS/AL. Also,
it's the longer curve. The black curve is EB-4, the CS/AL.
It is also the smoother curve. Both exhibit a rise around 5 khz
but can be tamed if preferred by using a second order low pass section
at about 4 khz.
Both curves were obtained with 0.25 watt applied with reference to the measured impedance at 1 khz. The EB-3 is 8.6 ohms and the EB-4 is 8.0 ohms at that frequency.
The mic distance was 0.5m and the generator was gated so as not to pick up room reflections.
0.25w at 0.5m is equivalent to 1w 1m.
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