Originally Posted by AspiringAudio21
Right now I have my mains and Sub hooked up in parallel to the L/R output of my receiver with speaker wire. If I took your suggestion and connected the mains to the subwoofer’s speaker out, then yes I could control the crossover using the dial on my sub.
It actually doesn't make any significant difference whether you wire the sub in parallel with the main speakers or wire the speaker outputs to the sub and then drive the mains with the sub speaker outputs. Either way, the subwoofer level and crossover control affect the subwoofer level only (almost). You definitely need to carefully set the sub's crossover and level controls to blend with whichever mains you end up keeping, but tweaking the sub controls will have almost no effect on what comes out of your main speakers.
I say "almost" no effect on the main speakers because some subwoofers do include a high-pass filter on the speaker level outputs to offload the mains from trying to reproduce the lowest frequencies that the subwoofer is taking care of and that your mains can't reproduce anyway. The advantage of this is that it reduces the load on your mains trying to produce frequencies they can't reproduce. In general, it's probably better to use the sub speaker outputs in case the sub does high pass filtering -- you won't hear any difference in what your mains produce, but they won't have to work as hard.
Originally Posted by AspiringAudio21
However, my question is- will I affect clarity by introducing another component and resistor (the sub) between the receiver and my mains? I will try it out myself but interested to hear if there are opinions.
This is not issue at all. The crossover in the sub is no different than the crossovers inside your Polks to control what frequencies are sent to the Polk's sub versus the Polk's tweeter. What you are avoiding with "direct mode" is digital manipulation in the AVR for bass control. If you are listing to a CD player through RCA jacks for example, the AVR is receiving an analog signal, but in non
-direct mode it will reconvert that signal back to digital, manipulate it in digital form for bass effects and whatever else, and then reconvert it to analog. That re-digitization of the signal, and manipulation in the digital domain, is what you want to avoid for music (the digital stuff is great for movies). In direct mode, the AVR should keep everything analog.
You don't need to worry about the sub controls adding an additiional resister -- the sub crossover circuit components are already in the signal path and are active, you are just changing the values of those electrical components.
You might be better off switching to the sub speaker outputs to offload your mains slightly if your sub does have a high pass filter. Regardless of whether you do that, definitely use the sub crossover and level controls to blend the sub with your mains. Don't think of the sub controls as affecting the mains, they don't do that, they are only there to modify how the sub behaves to blend with your mains.
The easiest starting point for sub tuning is to put the sub level at a fixed level -- say the midpoint, then adjust the sub crossover to the highest level where the bass is not boomy (boomy usually indicates the subs and mains are overlapping a lot). If the overall sound seems bass heavy, then turn the level control down, and tweak the crossover slightly again staying below boomy. If the overall sound is light on bass, the turn up the level and you may need to reduce the crossover frequency to reduce boominess. It will take a bit of iteration, but once you have it dialed in, you don't need to change it again ever (unless you later move or upgrade the mains).
There are a ton of people on AVS who know a lot more about sub tuning than I do -- hopefully they will chime in, but the above will get you in the ballpark pretty quickly.