[Elecraft] (OT) CW Resonant Speaker

[Dean L]

This whole topic is very interesting to me. Very ironically, just before
this topic got started, I was thinking about qrp hall of famer, Rick
Littlefield's,  Ham Radio magazine article Mar 89', featuring a resonant cw
speaker.
It was built using a solo 16 cup and a small 700hz transducer.
I put it on my to do list, back in 89'... nearly 28 years later I FINALLY
sent Rick an email asking if he still had any of these little speakers
left, after so many years... A few days later I had a package from Rick
with a couple of the little speakers!
The generosity of old school hams never ceases to amaze me.

I have a question for those in the "know"--

Knowing very little about the physics of sound, does using a thinner tube
as opposed to a larger diameter one, make the tube have a narrower "
bandwidth " ?
How would on increase the Q of the device ( if that's even possible)?

I'd appreciate any input. TIA

72
Dean/K2WW

On Feb 18, 2017 8:09 AM, "jrquark" <jamesforsman at me.com> wrote:

> The confusion here is a common one, closed vs open ended resonators,
> especially if one looks at the poorly explained graphs in most physics
> texts.
>
> The speaker, attached to one end of the pipe, is not the closed end, it is
> open, since it drives the air particles at that end, and that makes it a
> displacement antinode, where the particle displacement is maximum.
>
> Jim - K7BIE
>
>
> > On Feb 17, 2017, at 9:43 PM, Joe Subich, W4TV <lists at subich.com> wrote:
> >
> > A cylinder with a speaker in one end and open in the other is an "open"
> > cylinder (open pipe).  It is a *half wave* in air which means the
> > formula uses 2f instead of f.
>
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