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(OT) Follow-up on CW Resonant Speaker

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stan levandowski

(OT) Follow-up on CW Resonant Speaker

Folks, I posted about having built the CW Resonant Speaker in the
February 2017 and having problems with low audio. This is a follow-up
report for those with interest in this subject.

It works! It's fabulous! It's unbelievable how great it sounds! CW
pops out and background noise is significantly reduced.

I built it EXACTLY as described in the article and ordered the EXACT
parts listed. My problem was not enough audio coming from either my KX1
or my KX2 headphone jacks.

I purchased a fully assembled 15 watt mono amplifier - Qianson TDA2030A
15W Mono Channel Audio Power Amplifier Board AC/DC 12V AMP Module -
Amazon for $11.80.

With the new amp, my speaker is acoustically resonant at 760 Hz and I
have plenty of volume; enough to fill the room. The author had claimed
"around 700 Hz" so it's in the ballpark. I can verify that the
construction article was accurate.

I wanted 600 Hz so I built a vinyl sleeve to insert into the street
elbow and set my sidetone pitch for 600 Hz then slid the sleeve up and
down until I got a very obvious peak in volume.

I'm still a "can fan" for serious CW operating, but it's nice to be able
to listen to sweet CW that pops right out now that the higher frequency
sounds are substantially subdued.

This was a really worthwhile little project.

73, Stan WB2LQF
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efortner

Re: (OT) Follow-up on CW Resonant Speaker

Stan,

I have built three of the resonant speakers per the QST article. I am using a K3s and have plenty of audio without an amplifier. The three speakers were all in the ballpark of 700 Hz. I took a 2 inch coupling and put on the street elbow and it resonates at about 500 hz. There might be slightly more audio coming out of the external speaker but when the resonant speaker is switched on the noise level drops enough to be noticeable so the project was worthwhile.

Earl, K4KAY

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of stan levandowski
Sent: Monday, February 13, 2017 7:49 PM
To: [hidden email]
Subject: [Elecraft] (OT) Follow-up on CW Resonant Speaker

Folks, I posted about having built the CW Resonant Speaker in the February 2017 and having problems with low audio. This is a follow-up report for those with interest in this subject.

It works! It's fabulous! It's unbelievable how great it sounds! CW pops out and background noise is significantly reduced.

I built it EXACTLY as described in the article and ordered the EXACT
parts listed. My problem was not enough audio coming from either my KX1
or my KX2 headphone jacks.

I purchased a fully assembled 15 watt mono amplifier - Qianson TDA2030A
15W Mono Channel Audio Power Amplifier Board AC/DC 12V AMP Module -
Amazon for $11.80.

With the new amp, my speaker is acoustically resonant at 760 Hz and I
have plenty of volume; enough to fill the room. The author had claimed
"around 700 Hz" so it's in the ballpark. I can verify that the
construction article was accurate.

I wanted 600 Hz so I built a vinyl sleeve to insert into the street
elbow and set my sidetone pitch for 600 Hz then slid the sleeve up and
down until I got a very obvious peak in volume.

I'm still a "can fan" for serious CW operating, but it's nice to be able
to listen to sweet CW that pops right out now that the higher frequency
sounds are substantially subdued.

This was a really worthwhile little project.

73, Stan WB2LQF
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Elecraft mailing list

Re: (OT) Follow-up on CW Resonant Speaker

In reply to this post by stan levandowski

Stan,

Thanks for the video, most impressive.

I have one comment regarding the need for an amplifier with the KX1 /KX2 or KX3 radios, there is another YouTube video from a couple of years ago that appears to be almost what the more recent QST article is based upon and in it the constructor has it connected to a KX1 and it seems loud enough.

https://youtu.be/4iNELueaU6M

Then there is another video where another constructor dissects the original commercial design and makes one, this really shows how efficient the design is when at the end he compares the bare speaker on its own and how weak it sounds compared to when it resonates.

https://youtu.be/MF8bk6958Hg

The key seems to be that in both of the above cases the lower part of the resonant speaker is + not + sealed completely, air is allowed to enter and exit, though there is sound deadening material in the cavity. Perhaps that explains the greater sound efficiency?

This is something I plan to investigate myself with my KX3, once I get the parts here, of course being in the UK we are now metric and so some slight adjustments are necessary as our pipe is 50mm and so on. A friend has offered the services of his laser cutter and 3D printer which will come in handy too!

73 from David GM4JJJ

> On 14 Feb 2017, at 00:49, stan levandowski <[hidden email]> wrote:
>
> Folks, I posted about having built the CW Resonant Speaker in the February 2017 and having problems with low audio. This is a follow-up report for those with interest in this subject.
>
> It works! It's fabulous! It's unbelievable how great it sounds! CW pops out and background noise is significantly reduced.
>
>
> I built it EXACTLY as described in the article and ordered the EXACT parts listed. My problem was not enough audio coming from either my KX1 or my KX2 headphone jacks.
>
>
> I purchased a fully assembled 15 watt mono amplifier - Qianson TDA2030A 15W Mono Channel Audio Power Amplifier Board AC/DC 12V AMP Module - Amazon for $11.80.
>
>
> With the new amp, my speaker is acoustically resonant at 760 Hz and I have plenty of volume; enough to fill the room. The author had claimed "around 700 Hz" so it's in the ballpark. I can verify that the construction article was accurate.
>
>
> I wanted 600 Hz so I built a vinyl sleeve to insert into the street elbow and set my sidetone pitch for 600 Hz then slid the sleeve up and down until I got a very obvious peak in volume.
>
>
> I'm still a "can fan" for serious CW operating, but it's nice to be able to listen to sweet CW that pops right out now that the higher frequency sounds are substantially subdued.
>
>
> This was a really worthwhile little project.
>
>
> 73, Stan WB2LQF
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

______________________________________________________________
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html
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Vic Rosenthal

Re: (OT) Follow-up on CW Resonant Speaker

I built one once with a 2-1/2" (6.4 cm) diameter PVC tube. Unfortunately
I don't remember the exact length, but it was about 7" (18 cm) long. I
simply glued a 2-1/2" speaker to one end. It resonated at about 600 Hz.

At one point I placed a tightly fitting lid from a spray can over the
back of the tube and the speaker. It became significantly louder.

My experimental 2 cents.

73,
Vic, 4X6GP
Rehovot, Israel
Formerly K2VCO
http://www.qsl.net/k2vco/

On 19 Feb 2017 01:32, David Anderson via Elecraft wrote:

> Stan,
>
> Thanks for the video, most impressive.
>
> I have one comment regarding the need for an amplifier with the KX1
> /KX2 or KX3 radios, there is another YouTube video from a couple of
> years ago that appears to be almost what the more recent QST article
> is based upon and in it the constructor has it connected to a KX1 and
> it seems loud enough.
>
> https://youtu.be/4iNELueaU6M
>
> Then there is another video where another constructor dissects the
> original commercial design and makes one, this really shows how
> efficient the design is when at the end he compares the bare speaker
> on its own and how weak it sounds compared to when it resonates.
>
> https://youtu.be/MF8bk6958Hg
>
> The key seems to be that in both of the above cases the lower part of
> the resonant speaker is + not + sealed completely, air is allowed to
> enter and exit, though there is sound deadening material in the
> cavity. Perhaps that explains the greater sound efficiency?
>
> This is something I plan to investigate myself with my KX3, once I
> get the parts here, of course being in the UK we are now metric and
> so some slight adjustments are necessary as our pipe is 50mm and so
> on. A friend has offered the services of his laser cutter and 3D
> printer which will come in handy too!
>
> 73 from David GM4JJJ
>