is it ok to use y connectors?

[Sheep]

my hu an old sony has no sub outs

it has only 4chan out : chan 1 FL, chan2 FR, chan3 RL, chan4 RR

i got a 4 chan ampli

hooked the first to chans to the seps

as of now rear chans are hooked to 6x9s


planning to get either a pioneer tubular sub or targa stealh boxed sub tommorow

Q: can i put y connectors on the HUs rear out


EX.
HU rear out -<tubular sub w built in ampli
---< -< amplifier rear on Low pass = 6X9s

Or is there another way to hook tubular subs w built in amp either pioneer or daichi

:freak: