[CW] 600 Hz Resonant Speaker for CW - Plans

[Jeffrey Herman]

I'm wondering now if instead of what I wrote, the diaphragm was removed
and replaced with a non-magnetic diaphragm, with the center cut out and a
harmonica reed attached in the center so that it can freely vibrate at
its resonant freq'y.

I just can't remember the exact details of the article. But going on what
I  wrote below, I would use a nibler tool (not nipper as I wrote) and make
cuts around the center of the diaphragm so that you form a narrow finger
that would act as a resonant reed.

Let me search for that article.

73, Jeff KH6O


On Tue, 1 Sep 2009, Bob Good wrote:

> Jeff,  Can you explain a little more about the "reed" portion.  I cannot visualize the trimming but am familiar with the "cans".  Sorry but thanks for the help.....Regards,  Bob  K4BG


>   ----- Original Message -----
>   From: Jeffrey Herman
>
>    I seem to recall an article about a VERY narrow CW mechanical filter, constructed as such: Take a pair of old headphone "cans", remove the outer plastic ear cover, then remove the metal diaphram. Using a metal cutter called a nipper (?), trim the diaphram in such a way that, for the most part, just a reed appears in the center (the longer the reed, the lower its resonant frequency, and vice versa). Replace the diaphram and cover. Now that particular earpiece will only pass signals whose audio freq'y exactly matches the reed's resonant freq'y.
>
>   One of those "ah-ha" type of simple but effective projects.
>
>   73, Jeff  KH6O