Neutrik solderless Speakon connectors work quite well; they're almost entirely foolproof.

Crimped connectors are also excellent so long as you use a suitable crimp tool; the Klein #1005 that GM recommends is an industry-standard in the US and is available under USD40 at any big-box hardware shop. ALWAYS use a good crimp tool.

So long as you achieve a solid, gas-tight connection through proper crimping, solder flowing is probably unnecessary and may cause more problems than it solves, esp. at the DIY level.

BobR