speakers and cables

thanks @immatthewj that makes sense.

I do have this

except that it does not work https://outlawaudio.com/products/icbm.html

I bought it for $120 and it came busted and I can’t send it back. (Being poor stings twice - when you can’t buy things and then when you finally buy something cheap and shady and get scammed) But why should I complain, having two subwoofers is not a basic need 

And yes, my preamp has only one RCA out pair

Hmmm, I guess "Outlaw" was an appropriate name for it.

Did you get your subs working yet, via speaker wires to sub and out of sub?

I just re-read your OP, and out of curiosity, what is your second sub?

And your original (first) sub?

And also, since I am ASSUMING that your original single sub was hooked up and operating via speaker wire connections, is it at all possible that a problem is existing with the second sub that is causing the fuse to blow?

this looks also cool (but $ already too high

https://shopgoodwill.com/item/203575181

this looks also cool (but $ already too high

Okay, so that’s a low pass filter, which, if I’ve got this right and your sub is the same as mine, is the adjustable part that sets where the frequency that the sub reproduces will be cut off at..

"A low-pass filter (LPF) is a circuit that only passes signals below its cutoff frequency while attenuating all signals above it. It is the complement of a high-pass filter, which only passes signals above its cutoff frequency and attenuates all signals below it."

"I hooked them up was I went from the SUB SPEAKER OUT from both subwoofers"

You want to go to the sub INPUT not the output. Unless that was a misprint in your original post, using the output on the subs would blow a fuse.You would be directing the sub amps back into your stereo amplifier.