I use this 12 V audio amp. It would be easy to put it inside a speaker. It 
seems to vary in price a bit. Today it is $8.50, on the low side.

"DROK TDA7297 15W+15W Audio Power Amplifier Module AC/DC 9-18V 2.0 Dual Channel 
Stereo Amp Board"
https://smile.amazon.com/DROK-Amplifier-Amplify-Digital-Portable/dp/B00C4MT274/

At home, I stick it to the top of one of the speakers with velcro. Writeup is 
here:

https://observer.wunderwood.org/2017/03/04/speakers-for-my-elecraft-kx3/

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

> On Apr 13, 2018, at 11:32 AM, John Gibson <gib...@alma.edu> wrote:
> 
> Hi Robert,
> 
> Your proposed speaker looks interesting. Thank you for offering it.
> 
> My need is a little different. I want to use a KX2 for portable emergency 
> communication, powering it directly from a 12V lithium iron phosphate (LFP) 
> battery. For this application I would like to power an external amplified 
> speaker directly from the same 12V LFP battery. I would be rather not have to 
> recharge an amplified speaker's internal battery.
> 
> 73,
> John, no8v
> 
> ________________________________________
> From: elecraft-boun...@mailman.qth.net <elecraft-boun...@mailman.qth.net> on 
> behalf of Robert J. Morris <ag...@iloc.com>
> Sent: Thursday, April 12, 2018 1:06:25 PM
> To: elecraft@mailman.qth.net
> Subject: [Elecraft] [KX3] New Product: SPX3 External Speaker
> 
> I've built a prototype powered external speaker for the KX3, and would
> like some feedback on what folks would desire in terms of features, and
> whether folks would want to own one.
> 
> The speaker currently is designed to match the overall look of the KX3
> and PX3, and accept similar third-party panels and covers as for the KX
> line. Presently, it uses the same legs and feet as the KX3 and PX3, and
> is the same height and depth as those. There is one USB port for
> charging the internal lithium battery, and input and output stereo
> jacks. The speaker is mono. The output jack redirects the right channel
> from the stereo input for a second speaker, just like with the Elecraft
> SP3 and other similar external speakers. The speaker is amplified.
> 
> The SPX3 puts out a maximum of 3W, and is about as loud as any external
> radio speaker gets. Volume is adjusted by the KX3. It plugs into the KX3
> PHONES jack. There is a built-in low pass filter to reduce noise and
> improve the listening experience.
> 
> The prototype, as you'll see in pictures in the links below, is slightly
> narrower than the expected finished product. The speaker driver and
> on/off switch are both waterproof, but - just like the KX3 and PX3 - the
> case isn't. So, don't drop it in a lake. It will handle all conditions
> appropriate for the KX3, and is meant for indoor and outdoor use. Having
> matched the case design so closely to the KX3, it isn't as airtight as
> I'd like it, so the next prototype will have the case halves join in a
> more customary way, but remain the same dimensions and overall look.
> This will also improve ingress protection.
> 
> You'll see the speaker is not a polished finished product yet, as it's a
> rough first prototype made by hand. Your feedback will assure the final
> product is what you want gracing your portable shack.
> 
> Please note, the KX3 in the photo is only to demonstrate the speaker.
> 
> All feedback is welcome. Please let me know which reasonable
> enhancements or simplifications you'd like to see.
> Examples:
> * Would you want an output USB port to use the speaker to charge your
> phone?
> * Would you want to dispense with the built-in battery, and run it
> entirely from external power?
> * Would you want a second passive speaker driven by the first to save on
> weight and cost? That is, a SPX3A (active, with battery, charger, and
> amp) and SPX3P (passive, with only speaker driver)
> * If you're a KX2 user, would you like me to produce the SPX2 (also in
> development)?
> 
> Pictures:
> SPX3 with KX3: http://www.iloc.com/ag6zz/SPX3/AG6ZZ_SPX3_KX3.JPG
> SPX3 Left Oblique:
> http://www.iloc.com/ag6zz/SPX3/AG6ZZ_SPX3_LeftOblique.JPG
> SPX3 Right Oblique:
> http://www.iloc.com/ag6zz/SPX3/AG6ZZ_SPX3_RightOblique.JPG
> 
> 73,
> Robert (AG6ZZ)
> 
> SPX2, SPX2A, SPX2P, SPX3, SPX3A, and SPX3P are Trademarks (TM) of Robert
> J. Morris
> SPX2, SPX2A, SPX2P, SPX3, SPX3A, and SPX3P are Copyright (C) 2018 by
> Robert J. Morris
> ______________________________________________________________
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