QSC MX3000a Bridged Mode

Feb 11, 2018
So some guys put in 4 QSC MX3000's in bridged mode, each one powering a RS18 unit (2x18").

The manual describes when the amp is placed in bridged mode that CH2 receives a signal 180 degrees from CH1.

The positive of the speaker is connected to + on Ch1 and the negative of the speaker is connected to the + of Ch2.

However the Gain on Ch2 must be turned to full to receive signal from Ch1 ,which is used to set the level. The current setting on the amplifier is Ch2 gain is all the way DOWN whilst Ch1 gain is turned all the way up.

So what does that mean for our speaker friend which is only receiving signal on the positive line?
Apr 18, 2011
Well, I've never tried, but the speaker is only getting 1/2 the expected power (at best), and it is only moving 1/2 cycle. Either out from center, or in from center. In a higher bandpass you'd likely hear something, but in the sub region, the distortion is likely hidden.
Put ch. 2 up where it belongs, and I bet you'l hear lots of "It sounds fuller" comments (as well as "Wow, it's louder")
I have a bunch of EX-4000, which are pretty much the same animal.
Old iron, lot's of balls. The MX-3000A's have single power supply. EX-4000 have 2. I don't think that makes a difference here. I regularly run mine at 2 ohms a side, but I've never bridged them.