I also use three subs in my main system. If your room is symmetrical in any way. I would try and run audyssey with the front two subs as sub one, and the back one as sub number two, without the minidsp etc. you might find it’s pretty good. I also use a minidsp and rew, but guys like
@PENG and
@Pogre have for a long time said they can get close enough(I’m paraphrasing)without the mini.
What happens when you add subs, is like the law of averages. The more subwoofers you add, the more room modes are excited. That has the tendency create a smoother frequency response, without further EQ. Of course placement is king, so it’s not always that simple, but it’s especially true with corner loading, because even with a single sub, that will basically excite all the room modes at once. LP will be key with a single sub corner loaded, but as you add subs, the averaging will take over making the FR smoother throughout the room.
I see
@3db added a video for gain matching subs. While it may have worked for him, I dislike the practice. Imo, if you gain match, the room and placement has to be 100% symmetrical, because when you place the subs in there spots, they’ll be affected by their placement. IOW, if you set the gain on each sub in the center of the room, and then put them into their locations, individual output levels can change. Simply because of their locations. (Level matching VS gain matching conversions are all over the internet if you so choose)
So imo, level matching(with subs in their place) makes more sense, since your setting their output based on where they will be used, and how they’ll be affected by the room accordingly.
If you’re inclined to use rew and the minidsp with Audyssey, you can also get excellent results. The fact is you might have to experiment to find the best results. Again, I use three subs as well, with a mini and rew. Looks like this.
This is before I apply the house curve.