1960s Harmony H1270 Sovereign 12-String Resonator Electric/Acoustic Conversion Guitar

Hah! That title is a bit like word soup, huh?

This is a somewhat-beat-up old Harmony Sovereign 12-string that a customer sent-in for conversion to a resonator guitar. It took some stewing and some marinating and some mulling it over but I finally got it done for him and I'm very happy with the results. It's loud, it has its own sound, and plugs-in great as an electric or an acoustic-electric guitar beautifully.

I've done similar-style conversions on several guitars, but this is my first 12-string conversion. It's making me itch to make-up something for myself, though.

I'd bought a coverplate, cone, and associated gadgetry for this project a long time ago but sat on it for a long time because I just didn't have time to devote to figuring it out so it would be successful. In the end, though, the only "non-recycled" part that went into this were the coverplate, pickups, and wiring harness. 

When you're making stuff like this, there's a whole process of "think-and-change" that goes-on while you're making it. For example, I'd initially thought about using a "cookie tin soundwell" suspended from the top with a normal (but reduced-size) resonator cone inside. In the end, I used a "reverse biscuit cone" setup and recycled a full-size cone that I'd had spare in the workshop (slightly damaged) instead. This made the project simpler and better and it allows for an adjustable-height bridge (archtop-style) as well.

I have some photos and description of the install process beyond the "pretty pictures" part of the post, here, so you can see how I modified this and -- perhaps -- use the same methods for your own weirdo projects!

Suffice to say, the work involved was: a neck reset, fret level/dress, hole cut into the top to fit the cone, lengthwise interior support rod install (when you cut a hole in the top of a flattop and don't add a ton of reinforcement, do this, as it helps -- though the coverplate screwed to the top helps, too), wiring work, biscuit and bridge crafting, and setup. I also installed the lipstick magnetic pickup flush with the fretboard end for a nice, clean look. I'd even ordered some cool chrome rings to maybe use for that instead so it would match the coverplate, but I liked this solution better.

Strings-wise, this uses lighter gauges as you only want to tax the cone with so much tension.

It sounds loud and decisive acoustic, jangly and bluesy plugged-in acoustic, and chimey and punchy plugged-in electric. The controls on the lower bout are volume for the K&K acoustic pickup and then tone+volume for the lipstick magnetic pickup.

Ready to see the process?

Here's the cone install. I cut a hole in the top and then cut the "bent" edge of the cone off so I could flatten the "outer ring" of it. That's the part that sits on the top. All the tone/sound of a resonator is produced within that inner crimp of the cone so this is perfectly appropriate. This is an inverted 9 1/2" biscuit-bridge resonator cone that had previously had some "sink" right in the center of the cone. This recycles it and it's perfectly stable in this capacity whereas in its "original" configuration it was useless. That reads as: free to the owner.

You can see that I've already wired-up the single-sensor K&K pickup and the magnetic pickup at this point. I didn't reinforce the bracing at all but I did install that interior support rod. The thick coverplate screwed to the top will stabilize the top's "flatness" where the cone sits, so I wasn't worried about adding more bracing around the cone-hole itself.

Note that I've used the old top material (with its spruce bridge plate) to make a biscuit bridge!

Here's the old top material I cut the biscuit from.

Here's the fully-compensated, adjustable-height bridge. Note the recycled gold thumbwheels below it. These can be adjusted by using a screwdriver to rotate their edges. I find doing it with a finger a bit hard but at least it's more convenient than having to make a second saddle like you would on a normal resonator setup.