speakers and cables

Grizzly, let me add two more things:

what I described in my last post was a diagram showing how to use only ONE sub.  However, I truly do not think that it would change if you were using two subs, except that you would not use both left and right ins and outs from one sub--in other words left sub would use only left in and only left out/and then the same for the right sub to right speaker.  Sorry because I know that this is way more than obvious, but I felt the need just in case.

The second thing is my manual shows a second option with speaker wire, BUT this is for amps or receivers that feature an OUTPUT 1 (for speaker wires) and ALSO an OUTPUT 2 (for speaker wires).

I am going to assume that you do not have that (I don't think I've ever owned anything that had that) but just in case:  that diagram shows OUTPUT 1 (speaker wires)  hooked to L & R speakers as per the usual way, and it shows OUTPUT 2 (speaker wires) hooking to the speaker wire inputs in the sub.  And note that in this configuration, the speaker wire outputs from the sub are NOT being utilized.  And again, this diagram is for only ONE sub, but if two were being utilized, obviously one sub would connect to L and the other to R. (Even though I know how obvious that is.)  So I am pretty sure you don't have two sets of speaker wire OUTs in your amp, but in the way way way off chance that you do, there is also that option.

Few bucks of fuses are not the end of the World.

Hopefully you have not been using fuses that are orange, purple, or blue?

@immatthewj 

you are very thorough and kind and helpful. I have exactly what is on the photo I included.

It's this model. 

https://www.polkaudio.com/en-us/product/home-speakers/subwoofers/psw-10/112479-new.html

it has RCA in, LFE inputs too. (And they sound great to my ear)

Just did this with my new (to me), no frills, Don Sachs integrated.  +1 noromance, Pic 2.  Worked like a champ.  Pic 2 preseves any notion of stereo for the subs.  In my case, one sub didn't have Hi-power inputs so I had to use a speaker to line-level converter.  EZ PZ.  

Griz, I am intrigued by those Polks. My M&K is ancient . . . it was the piece of gear that started me down this road to hell. I think that was near the end of ’93, either that or very early in ’94. M&K (apparently at least at that  time) didn’t believe in fancy power cords. Hardwired from the amp section is not much more than lamp cord with a two blade plug. I have no doubt that my sub is the weakest piece of my system, and it has been for some time. As I typed, I am intrigued by those Polks.

I do need to correct something I typed about the high pass filter. At least the one I put a link to a picture of. I said it rolled off the bass to the sub. That was incorrect--a low pass filter would roll off the bass to the sub. That high pass sends the full signal from the the preamp out to the sub, where the frequency is then adjusted at the low pass that is integral to the sub.

(I got curious so I dug out the high pass filter instructions.) So what the high pass filter therefore must do (although I cannot find this spelled out) is to roll off the bass FROM the preamp TO the amplifier (and therefore the speakers). But, I am not sure at what the frequency cut off is that it allows to the amplifier. But the idea is to provide a cleaner separation of bass between the speakers and the sub(s).

Oops! So I’ll insert an edit: I just did some searches only to satisfy my own curiosity, and evidently that particular high pass filter is set to allow 80hZ and up FROM the preamp To the amp (and therefore the speakers).

Not that this is applicable to you; however, since I typed it and got it wrong but can no longer edit, I just felt the need to correct that part. Ramble on. . . .