Center channel used randomly

I use a 4 channel - wav file in a Studio event which is distributed correctly to the two front and the two surround speaker channels (channels 0, 1, 4, 5). In order to have an output on the subwoofer (channel 3) I created a Mix Matrix that takes 25% of each input channel and routes it to the subwoofer channel.

However it happens randomly (NO changes in the code) that the center speaker also shows a signal and sometimes not. Setting the respective entries with setMixMatrix to 0.0f for the center (channel 2) has no effect.

My System:

Windows 7 32 bit
FMOD Studio API 1.04.04
ASIO driver
Sound Interface: Focusrite Scarlett 18i20

Thanks for your help in advance!



When I disable the center speaker in Studio, there is never an output on the center speaker.

HOWEVER: It happens randomly that the front channels have higher volume, the surround ones lower volume as if the center channel was correctly disabled. But it also happens that the volumes stay the same just as if the channel was still used, but no signal is getting to it.

All this only happens when my application is started over, during runtime the behavior stays the same!

Update: When I play an event with 3 channels (3 channel wav file used in a Studio event) the channels get assigned to front left / right and center. The center channel fades to zero after some parameter updates but stays the same if no parameters are changed. This does NOT happen to the front left/right channels so something must be wrong with the center channel as they are treated exactly the same.