The Art of the Bodge

Getting ancient (older than me) big-ass radio speakers to interface with a humanly-accessible standard

Well ain't that just a breeze of a title? Anyway, hello and welcome to The Art of the Bodge, as inspired by an analogously named video from Tom Scott, wherein I (and hopefully other people, I love seeing folks' DIYs/bodges) arrive at a dead-simple solution to a problem (and then pay the piper).
Right, so with that in our think-cushions and a depressive episode out of the way, let's get crackin' on to the meat of this installment (for some definition of "cracking on").

So, when father was digging through the basement looking for god-knows-what (he's the weirdest things), he called upon me when he ran into some speakers I requested be set aside at least three-four years prior when some old radio we'd had had given up the ghost.
Now, the big part of the living room here is the distinct lack of any good speakers, with some garbage PC speakers in the stead, so, I thought, "why not put those there" (boring) and figure out the funky connectors (fun!).

Fig. 1: both connectors, three out of four holes plugged, leftmost wire tinned.

The connectors are made of some kind of black plastic and pokey bits (we're all professionals here, right?) somewhere deep on the ID. Now, the holes looked weirdly close, size-wise, to some 2.5mm² wire I'd purchased long prior (it's a surprisingly good structural material, striking a good spot between hand-workability and stiffness, be it for a reaxion flask or hanging a welding mask on a garment rack).
And, whaddayaknow, they fit! This means that the hole size is, roughly:

Fig. 2: formula for the wire diameter/hole side, yielding ca. 1.784mm.

Which also finally, with the speaker size, disproves my hunch that this would be an American product – neither is 1.784mm reducible to a multiple of a binary fraxion of 2.54, nor do any dimensions (that is, 175 x 205 x 277.5), make any sense in an imperial reference frame.
Anyway, the plan from now on was, en théorie, simple: tin the business end of the infit (already done on the leftmost one in Fig. 1) and solder two pairs of a ribbon cable to the two connectors.

Fig. 3: both connectors tinned & with soldered wires, rightmost one left unplugged; note how the left pair is touching.

(It was not simple, though, because the whole bloody thing behaves like a huge heatsink and keeping it at temperature was a nightmare.)
Now, there are two problems here: the clearly evident one is the short between the terminals on the left.
That would've been solved by America's second-favourite libation: a heatshrink. However, it turns out I don't actually own heatshrinks this large (it's not every day that you heatshrink a 20A-rated cable), therefore it was necessary for me to turn back to the spawn of Satan itself – electric tape.

Fig. 4: all connectors wrapped in electric tape.

(Chunk one of two, got hit by size limit) #art-of-the-bodge #electronics #diy

That was easy enough! After soaking out the filth that electric tape left on one's fingers (and, more importantly, their soul), the second problem can be tackled: the standard interface. Now, every end-user audio device has a 3.5mm audio jack, so that's definitely what will be used à la fin, however, while hard-soldering one to the ribbon ends is definitely possible, it's unviable: not only does it define the speaker chirality (unsure what the professional audio term is) (not that it matters, though, despite however cold the joints might look, I measured the resistance and it's within tolerance), it's also prone to breaking, so the obvious solution and the second standard employed will be the electronics' gold- standard and pin.
Au première, though, tests were performed to see whether the TV can drive these massive speakers without external power (i.e. whether transistorbs were needed) and thankfully it could, so I managed to avoid designing an actual board for this, and instead I could just opt for…

Fig. 5: the adapter board layout.

This dead-simple "design", with a common ground rail and two double headers tapping thereinto…

Fig. 6: the perf board, scored.

So naught was left but to score a perfboard to size with a knife…

Fig. 7: the perf board, cut and sanded.

And one-inch-punch metal-saw it over the score lines, then sand the sharp edges over.

WARNING: fiberglass is a known carcinogen, and if you don't have lung protexion the cut should be performed manually rather than with power tools, away from areas where people eat &c., the sanding step should be performed outside or in a fume hood, in both cases care should be taken not to inhale the chips/dust.

Fig. 8: the board, both sides up, with goldpins soldered in.

And here's the board after soldering and washing, I chose M on the board and F on the cable as personal preference, actually, how's those doing?

Fig. 9: connectors with female goldpin 2x1s.

And that's that! Now there's a way to connect the speakers through their proprietary connectors to a 2.5mm² wire to a ribbon cable to female goldpin to male goldpin to 3.5mm audio jack (oh god I'm getting flashbacks).
Now that I wrote that I actually realised I didn't shoot the jack wiring (because I already had a test one when building this (and the second one is, honestly, a bloody disaster of a solderjob)). Oh well.

And how's the thing sound? Not as bad as I'd've thought it would. And anyway here's the final demo video of the thing working:

(Warning: this camera was pretty good for a photo cam in 2005, but y'know; I did my best though)

(Chunk two of two, got hit by size limit) #art-of-the-bodge #electronics #diy