I would be very surprised if Speaker4 is mono!

As far as I have understood in Speaker4-mode the music is sent in stereo to the front speakers (excluding the centerspeaker) and in stereo to the back speakers.

That is exactly what i knew. He was confident though, that in SPEAKER4 mode, we hear 4 x MONO channels. 

Your dealer is wrong. Just checked my manual:

SPEAKER 4 : Enhanced stereo sound in the front and rear speakers. The BeoLab 2 subwoofer is active.

LOL. I could not resist. i'll call you again!! 😕

i used to use speaker 4 when i had lab 8000's at the front and 6000's at the rear as it fileld the room, i did notice that on speaker 4 the sub was extra loud than if using speaker 2

now i have lab 9's i have not touched speaker 4 since.

I would never want to 'listen' to stereo music (ie, non-surround-sound content) in speaker 4 mode. For parties, yes, and for background music, absolutely, but for true 'listening' - never.

Why? Well firstly the sound is arriving at your ears twice. Usually, the rear speakers are closer to your ears than the front ones, so the sound from these will reach your ears first. This 'smears' everything - recording engineers go to great length to make sure the sound from each instrument isn't arriving at loads of microphones at different times in a disturbing way (bear in mind sound actually travels quite slowly!) so you are presented with the 'truest' sound when sat in front of your speakers. Playing through 4 speakers completely destroys this!

Secondly, you lose any sort of stereo-image with speaker 4 mode. Stereo sound is formed by two sound points (speakers in this case) both reaching your ears, with the sound from the left speaker reaching the left ear first, then the right ear, and visa-versa for the other speaker. Adding in a second pair of speakers (which are often positioned less than optimally) and you start to get the idea - the more speakers reproducing sound, the more 'diffused' and less 'defined' your sound becomes!

Ultimately, it's all down to the discretion of the listener. Listening to stereo through 4 speakers would be absolutely laughed at by most people in the professional/hi-fi world though - it's a very 'multimedia' thing to do, with all except the most ambient of music (think Brian Eno).

i agree completely with you Alex,my config is beolab 3 on front and beolab4000 for rear.

but.......i've to say that sometimes i've used config SPEAKER4 than 5.1 watching a movie, it was really amazing...of course it was a wrong setup,expecially when there's dialogues in the movie...but in war scenes it was more involving!!!!

I agree with you Alex.

Usually, the rear speakers are closer to your ears than the front ones, so the sound from these will reach your ears first. 

However, I always thought that the sound is delayed, if you setup the distance in the sound settings, from every individual speaker to the sweet spot.