Correct, there is no mono out and the Series III rack mixers have no Low Pass Filter. There are 6 band parametric equalizers on each output, but they can not do what a LPF can do.

You will need to sacrifice one or two of the flex mixes and use them as aux-subs. The result will sound different, because normally you will NOT send all input channels to the aux-subs and cut the full frequency range. You will probably choose bass, kick and other instruments with "deep" tones and resonances, and leave the rest like guitars and vocals away. If you are using bass speakers, frequencies above 120 or 150 Hz can anyway be neglected. Physically/acoustically there is not necessarily a need for a LPF. If there really is a frequency range too crowded, simply use the parametric EQ to notch these frequencies out.

May I ask, what kind of music are you dealing with?

I do all purpose sound re-enforcement. I’ll just continue using a crossover I guess... Why would they leave out such a basic feature that every other console on the market has???

Interesting, I don't see any mixers (consoles, rack mixers) on the market with an additional mono output. They all seem to miss this "basic feature", so the Series II mixers fit into the picture. Most of the modern mixers don't even have L/R outputs any longer...

I can understand that your are missing a nice feature from the "old" rack mixers. The mono output is also very useful for center and front fills, as the mixer has the LCR (left, center, right) option. Using an electronical crossover is a "traditional" solution, but it makes you carry more stuff and connect more cables. We are now designing digital workflows, so I would recommend to look for a solution within the digital (PreSonus) world. An aux-sub can also be fed by a matrix mix, if that makes sense sound-wise.

But there is also a very conventional and cheap solution: Just use passive cross-overs in your bass bins. Then you don't need to worry about LPFs...

Just my 2 Euro cent.

Crossovers help with amplifier efficiency. By cutting out those frequencies that aren’t required before the amp processes the signal. And the feature I’m meaning is a low pass on an output. Most boards have this option. Especially at the professional level

I use one of my “Aux” Sends to feed my subwoofers. It works almost the same way as mixing stage monitors, but goes to the subwoofers out front.
You can send just what channels you want and you get the “Fat Channel” to EQ things as you want.Then if you use the “Custom User” layer, you can put the fader where you want.

Many powered subs have a built-in crossover that you can set, then you can play with the EQ to shape the sound, so a crossover is not really needed on the board. You can also crank up the low end on songs/tunes that want it or back off on others that don’t want or need a lot of low end.

Using an Aux send gives you a lot of control....

And don’t forget to take the “Low End” out of your Main speakers when using subwoofers. I usually take out everything below 100Hz in the mains. Let the subs do the low, low end work. Taking the lows out of the mains lets those woofers handle the other frequencies cleaner.

Setting the aux to post and the channels you want in it to 0dB and it will nicely follow your main mix.

I'm a driverack guy.

I could never be happy with an Aux fed sub.

My crossover runs at 48db/octave! Now THAT's what I call a crossover!

That said I do not have powered subs with crossovers built in, so I have to use a crossover. But with the amount of fexibility my DriveRack 260 gives me, I'd still probably use it with Powered subs too. . .

I didn't even know there was a Low pass filter on the mono out of my RM32, hmmm, that could come in handy some day. . . maybe. . . it's prolly 12db/octave or something silly like that

Steve