A wiring (resistance) issue.

Long story . . . I obtained a JVC 6ohm front-loaded, ported subwoofer with a seemingly incurable rattle. As with many big-box products the unit cannot be disassembled. Rather than throw it out, I did a thing. I found some feet, cut a hole in the bottom of the cabinet, fixed the rattle, and installed another 6 ohm driver into the hole I'd made.
It all sounds great but it's 3 ohms and I don't know how much longer the amp can cope.
I could wire the drivers in series: 12 ohms. Or, I have a 5 ohm resistor that I can utilise. How can wire these to get close to 8 ohms?
 
Use a higher rated Class D amp, as the existing amp is near its limits.

ST had some automobile use chip amps which are rated at 1, or 2 ohms. Their competitors would also have some.
It seems the trend now is for lower impedance rated systems.

I was looking for chip amps on the ST site, most are Class D, and rated for much lower impedance than the Class AB amps.
No ties to any seller, YMMV.
 
Thanks guys. In the end I wired drivers in series. It sounds okay. tighter. It was an interesting project that saved a speaker from the scrapyard. The cabinet is probably too small, 2 x 6.5" drivers in a 18l box designed for one. It has the trifecta of options: front-facing driver, downward facing driver, rear facing port.