Hi, ill try and answer your question for you but first id like to ask something. Why do you want the centre speaker connector? I'm my experience the gain from this will be non-existent. When you connect stereo speakers and listen to them sitting in front of them between them you experience something called a sound stage. This essentially sounds like the sound is coming from directly in front. I wouldn't advise connecting the speaker channels in that way either because you are bridging the two separate channels which will do more harm than good. If you REALLY want a centre speaker then id suggest getting a bi-wire able one where the two drivers in the centre speaker have separate connectors and you can connect the left channel to the left driver and the right channel to the right driver.
Im not sure what set up you have or anything but remember its more damaging for a amplifier and speakers if the amp is not more powerfull than the speaker output. It wont do much but if you want to get real nit-picky then that is the way to go about a stereo and speaker set up. If you want the sound to come from directly infron i suggest you play about with the position of the speakers. Possibly move them away from the wall behind a few inches at a time and toe the speakers in a couple of degrees at a time untill you find that the music sounds like it is coming directly infront of you rather than from the speakers.
What amp/speakers do you have etc it might help solve the problem but if i were you id ditch the centre speaker. Im fairly confident you can achieve what you want with just the two mains with a little adjustment.
Spec....
please feel free to pm me if you want to talk about this more or discuss stereo talk 👍
