What interconnects are you guys using for bi-wiring speakers? I need a Y XLR based cable.

I've never done that, but I suspect you would do fine using an XLR cable of your choice in combination with a pro-oriented XLR y-adapter such as this one:

https://www.bhphotovideo.com/c/product/134966-REG/Pro_Co_Sound_YMXF2XM_1_XLR_Female_to_2.html

Keep in mind, of course, that regardless of what cabling approach you use your preamp will see a load impedance equal to half of the input impedance of a single channel of your amp.

Regards,
-- Al
 

OP... What PreAmp are you going to be using in this setup? Does it have X 2 sets of XLR Outputs, each with plenty of voltage so you can feed a proper signal to each of the Amp Inputs?

If you don't have X 2 pairs of XLR Outputs on the Pre I wouldn't attempt this arrangement as the use of splitters are a true hack job IMO.

I ran a similar arrangement in the past with X 4 Monoblcks and a pair of B&W 803 D2's using a Classe CP-800 Pre with good success.

This PreAmp has multiple XLR Outputs and a total of 18v on tap at the Outputs to drive multiple Amps correctly.

If you're using two amplifier channels per speaker, that's biamplifying, not biwiring. If that's your plan, you should consider using an active crossover. That's the way to get the most out of biamping.