Now, focus on the crossover frequency range on the display while you make changes: crossover frequency, gain levels, slopes, splitting the high and lowpass points, reverse polarity on speakers, etc. Look for the smoothest frequency response possible, but be careful not to overdo it while trying to get the RTA curve perfectly flat. Remember, in the end it matters how it sounds to your ears not how the dots on a visual display line up. And when tweaking the midrange-to-weeter crossover with an RTA, again work with only one channel at a time.
Don't forget to try reversing polarity on the speakers on either one side of the crossover or the other, especially if there is an apparent deep hole in the frequency range near the crossover point that does not go away by changing the other crossover parameters. The hole may be caused by the destructive combination of the higher and lower frequencies from the different speakers at the listening location. Reversing polarity may improve the response or it may not. But give it a shot.
As always, your ears are the final judge! Document your settings and then go back through everything while listening to the system, make some changes and see if you can improve it further. Look at the RTA as a time-saving tool to get you deep into the game quicker than using just your ears. But also remember if the RTA curve looks good but it sounds bad, trust your ears. You won't be driving around looking at an RTA - you'll be listening to the music.
Wrapping It Up
Document your settings as you go. Don't be afraid to set everything back to zero if you get to a point that just isn't working. Take breaks, or even put it away until tomorrow if it's just not coming together. If you're not pressed for time, take your time. It will make a difference.
Of course, you'll make further changes to match your personal taste over the course of several months, but these techniques will help you get to a point where it's close and you'll know what you've got. Then, it's a whole lot easier to make it sound like what you want it to.
Until next time, good tweaking!