If you know all this already, I apologize in advance for bringing up what may be basics to you
Several things to consider:
Bass nulls are a normal part of all rooms with all speakers. For every frequency in the bass region, there will be places in your room that will sound loud and places that will sound low. Where you place the subs and where you listen completely determine whether you are in a peak or a null. In my room, if I move 2 ft forward, I get a "little more" bass.
Make sure you are pointing the calibration mic at the ceiling, level to the floor, right at your listening position, at head height and not aimed or tilted to the front.
MCACC's only applies an EQ to speakers, not the subs. All MCACC does with sub outputs is adjust the output levels & distance.
There is an optional Standing Wave correction that is turned ON by default. It is supposed to help smooth bass peaks & valleys at 3 freq settings that are auto-chosen and a boost or cut is applied. If it's ON, try turning it OFF and vice versa. This may help. Or you can adjust the specific frequencies manually.
There is an optional Phase Control feature which is supposed to help correct phasing across speaker drivers & for bass. Try turning OFF if turned ON or try turning it to just Phase Control and not Full Band Phase Control.
While Pioneer's standing wave option can help smooth out response, it will probably not correct a big null. For big nulls, you need to -
1. Try moving the subs a little to minimize the null at your listening position. You may need to move both subs or just one of them.
2. Move your listening position.
3. Use a parametric equalizer for the 2 subs that you can adjust manually. This can be a BIG help. Keep in mind that no amount of boost can completely eliminate a frequency null. What they CAN do is smooth out the response so that nulls are reduced & less noticeable - minimize the differences between freq. peaks & valleys.
There are several EQ's on the market that will significantly help you with your problem. Probably the most user-friendly & complete sub EQ on the market is the Velodyne SMS-1. Outlaw Audio is one source for the Velodyne. No matter how you set up your SC-09, I'd highly recommend the SMS-1. I have the same EQ functionality in the Velodyne sub I use & it works wonders!
All this being said, if you want to try tweaking MCACC settings, you could try manually adjusting the standing wave filters. You can also try setting both subs at the same dB level, using the higher of the 2 as the setting for both. To do this, go into manual MCACC mode, select each sub, and change its output.
My best advice for getting optimum bass response in any room with any sub is look at getting the Velodyne SMS-1. You won't regret it http://www.velodyne.com/products/pro...5&sid=965a752k