Q. Can I join my QED loudspeaker cables together to make them longer?
Answer:
Regarding connecting cables of the same type, whilst you may find it
physically possible, this is not something which we recommend or
support as in
doing so, you would be interfering with the optimal performance of the cable.
Although we do not support the idea joining cables together, if you have no option and are willing to accept the above, we'd suggest using banana plugs at the ends to be joined and then use a coupler like this
https://www.ebay.co.uk/itm/252642291225 , or if happy to use bare wires, then standard electrical choc bloc.
Soldering two large cables like ours requires a lot of heat and you can never get enough in the joint to get the solder to flow all the way through so, it tends to end up joined only on the outside. At the same time the heat hardens the copper and makes it brittle and more likely to snap at the join.