I started with measuring the response. Pretty flat since I had already set the main EQ stuff a couple of days earlier. But there was lots of room for improvement and I still have some nasty stuff going on at ~90-400Hz.
Today I have tried different crossovers, inverting phase and fine-tuning the EQ. This is the result so far, presented with 1/24 smoothing.
Right now the subwoofers are crossed over at 120Hz with a 24dB/octave Butterworth filter. The main speakers are crossed over at 80Hz with the same type of crossover as the subwoofers. Might be it's better to set it a few Hz higher to flatten the tiny peak at ~84Hz. And by the way I don't think the graph can be trusted below maybe 30Hz because right now the fans of the Behringer amp is blowing straight towards the mic (I have the muff on) but the background noise is slightly high because of it.
I also noticed an electrical buzzing sound coming from the Behringer, from behind the power button. It doesn't sound very healthy so I'll contact Thomann about it. I don't want to switch fans if I have to return the amplifier.
Speaking of fans I have decided to use Fractal Design 1400rpm 80mm fans. I bought one for cofffee-money from my friend Robin and I have ordered a second one from CDON. Hopefully it will arrive before the weekend. While searching through my boxes for some cables I stumbled upon two pairs of Noctua low-noise adaptors (basically a 3-pin 10cm extension cable with a resistor mounted on it) which will come in handy if I need to reduce the RPM of the new fans.
I guess I don't have to say it sounds really good now that the massive 50Hz peak is gone. There's more nuances in the bass now, it's not that one-note bass any longer.
Edit: Here's another picture with phase included.
Edit #2: I did some close up measurements of the right channel speaker.
|This is with the mic 10cm from the upper woofer, on-axis. Only right channel speaker playing and being measured.|
|This is with the mic 10cm from the tweeter, on-axis. Only right channel speaker playing and being measured.|