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. . . .