This system has Realtech HD Sound as well as every new system that I've built recently. The sound isn't too much of an issue for me and can be turned up quite loud though if you select Sub Woofer only Low Frequency Bass should be feed to that Speaker so you may not get much noise at all and there will be no Highs.
Only thing I can think of here is that the driver is somehow wrong so if you have downloaded the newest driver try using the one that came with the M'Board Disc and if that doesn't work I would try another set of Speakers. I'm not a great Logitech Fan as I've had numerous problems with that brand equipment and when one set of 5.1 Speakers feed Mains Power back into the M'Board and fried it that was the last straw for me.
Well I wasn't so overly upset about the destroyed M'Board but the 220 V DC Shock that I got from the Speakers really peeved me off. Apparently the only thing still working in that set of speakers was the Bridge Rectifier so instead of getting hit with AC I got a DC Shock which is far more likely to kill you.
Maybe it was just the Electrical Inspectors that came out after the Meat Wagon was trying to take me away which was the last straw or the fact that the speakers didn't have the correct Electrical Labels on the Power Unit so they where not approved to be imported into AU. But ever since I now look at the actual Speakers and make sure that they have the correct Specification Label on them or I don't even consider them as a option.
Col