Subwoofer

Can I hook up A  third subwoofer

Thank You

Run the left line of the y cable to the left sub, the right line to the right sub.

it has bass level +15

Connect left from source to left input of sub 1 and right from source to left input of sub2.

I do not understand

Am using Y cable on the back  of preamp and running RCA CABLE TO THE 1ST SUB LINE INPUTS  What next

If it’s the true subwoofer junior you also have speaker level inputs and can connect directly to those using the left speaker level input on both subs.  So right speaker output from source to left speaker input on right sub and left speaker output from source to left speaker input on left sub.

Connect left from source to left input of sub 1 and right from source to left input of sub2.