The OP is trying to avoid buying another 4M cable from the sound of it. The Y connector should 1M>2F with the male plugged into the amp driving the high frequencies, and the short cable into the low frequency amp, assuming passive biamplification is the objective. A preamp with dual outputs effectively has a splitter built in.
Splitting line level out from preamp, versus using 2nd set of outputs
I'd like to add a line lever splitter between my preamp and amplifier, close to the amp end on a set of 4 meter interconnects and send signals to two amplifiers that are located near to my speakers, versus buying another 4 meter interconnect to drive the second amp from the second set of line level outputs on my preamp.
I'm considering asking the interconnect manufacturer to make me a set of female to 2 female splitters out of spare set of interconnects. I'd use two one meter pairs of the same interconnects to feed the amplifiers.
These are RCA cables.
I know that it can be done, my question is, am I setting myself up for disappointment?