Subwoofers masking other frequencies.


Bought a third sub,a svs sb2000 to add to my existing 2 subs hoping for stronger and more detailed bass response. My mains are magnapan 1.7i driven by parasound A21 +. After messing around with  different ways to intergrate the subs I realized some parts of the music was missing or reduced in volume or one channel was stronger .well I turned off one sub at a time and the sound was full. Is this common and what's the remedy for this phenomenon. 
Thanks 




audiomaze
 The phase knob mostly affects the blend between subs and mains.  When it SOUNDS right, it IS right.  There are too many variables to predict in advance what the "right" setting will be, but in the end what matters is how it sounds.  Don't be afraid to make big adjustments.   

Duke
I took your advice and set the crossovers to dead bottom and slowly increased volume  winsome good results. 
Thanks for your help Duke
@audiomaze 
Yes, Audyssey will help you, but it is still a starting point. I don’t think it does much in the time domain. You will need to raise the level a couple of dBs from what Audyssey recommends for it to sound realistic. Good luck.