In the control room, selecting A, B, C or D speaker outs. Is there a way to combine two or more
speaker outs at the same time? Thanks…
No, there is no way to do mix and match and play different monitor channels simultaneously.
You COULD use the Phones channel to run a separate set of speakers at the same time as a monitor channel though. Only issue is that the phones channel would be dedicated to only one set of outputs, so you could say… put your main speakers on the phones channel, and then have your additional pairs of speakers on the monitor channels that you could swap between to play WITH your main speakers. Or you would do whatever would be the best compromise for what you’re attempting.
Of course, since the phones channel and the control room channel can be separately controlled (and can have a separate source input) you’ll want to make sure both the phones channel and the control room channel are each playing what you want them to play when playing them together. I realize it’s not doing exactly what you want, but it’s a possible work-around depending on what you want to do. ::shrug::
Just in case you are asking whether it’s possible to allow the same speakers to appear in two different monitoring profiles then, yes this is possible.
preferences->VST->Control Room-> uncheck Exclusive Device Porst for Monitor Channels
You could also define a Monitor set with a 4 channel configuration.
See the Op Manual Pg.220(Eng) 
I don’t think either of those solutions will address the OP’s question. Disabling exclusive device ports for monitor channels would only allow him to put the same speakers on different monitor channels, it wouldn’t allow him to play the same material on multiple pairs of speakers in an independent and controlled way.
And creating a quadro channel monitor wouldn’t work either, unless the channel that is feeding the control room is quadro also. Assuming his main output is stereo, only the first two channels of the quadro channel would play that stereo signal, the other two channels wouldn’t know what to play, and there’s no mechanism to tell them to duplicate the stereo out. Mixconvert only mixes down, it doesn’t “mix up”, so there would be no way to tell the quadro channel to duplicate the stereo signal from the control room across both pairs of the quadro channel.
So in order for that to work, he would have to duplicate the signal to a quadro channel PRIOR to it reaching the control room. Totally doable, but then your main mix channel becomes a quadro channel instead of stereo, which adds complication to your mixdown process.
I could be wrong about all that (or misunderstanding the original question)… and I’d be interested to know if I was. 
That said, if you weren’t using the Cue Mix channels (a.k.a. Studio Channels under Cubase 6) for anything else, they could ALSO be used just as the phones channel could be used for this purpose (as I mentioned above)… so you could in effect have 6 sets of speakers that you would have independent control over, you would just control them with the on and off buttons of those respective Cue, Heaphones, and Control room channels rather than the monitor preset buttons. A creative use of the control room, but a use nonetheless.
I concur, the cue’s or sends would be the most rational approach to this solution within Cubase. Personally I would (and do) go for a hardware solution such as a Bigknob (I use a UR28M) both of these would allow simultaneous listening with 3 pairs of monitors, but even a signal splitter (Y-cable) would probably suffice for combining 2 pairs.
Thank you for you’re replies.
I’ve used the Phones panel since I didn’t use it anyway.
now I have complete control, I can play two sets of speakers
with diferent plug in settings and volumes for each set .
doesn’t the focusrite allow it through the mixer setup at all ? Motu does through the cuemix .