strange 5.1 output configuration

[raindog]

Hi everyone,

I've taken apart my 5.1 PC creative inspire p5800 ( not exactly audiophile but ok for 100$ ) in order to do some tweaking ( i've recently got a audiotrak prodigy 7.1 hifi soundcard so i thought that some upgrading of the speaker system was in order ). While I was studying the pcb ( nothing spectacular : two tda8947j amps, a few opamps two volume control ICs and a jrc 4558 as the headphone amp ) I've noticed something strange : the rear left output plug is wired in reverse phase to the rest of the outputs ( they are all RCA plugs soldered to the pcb so this is done intentional by the manufacturer and not a manufacturing mistake - and the front and rear speakers are not marked , any of the four speakers can be used with any rear or front output ).

I was wondering if anybody knows if there is a reason behind this "mistake".

best regards

Paul

[raindog]

I've done some more research (googling mostly )and aparently having the rear speakers in oposite phase makes the soudstage wider ( based on the research done with the passive haffler matrix ).

[AndrewT]

Hi,
adding the out of phase rear speakers to a two channel Stereo signal was quite normal.

5.1 is a dedicated 6 channel sound system. It does not need a matrix system to generate any special effects.

[raindog]

Hi Andrew,

I think you are right, but my guess is that Creative tried to make a fairly cheap and "lo-fi" system sound better ( they do-it whith their sondcards - a good example is the x-fi cards ''crystaliser'' ). I was just wondering if it's worth modifing the pcb so the rear speakers are in phase; I only use the system for movies and ocassional gaming.

Paul