[Huck]

Inside a chassis the pin#1(shield) should only be connected to the chassis (with a very short jumper) but not connected to the circuit common(Ground). Yes the circuit common(Ground) is also connected to the chassis but that's a different story. In pro audio the XLR shell/barrel is not connected to the shield, but the reason is that with all the long extension interconnect cables the shell could contact metal at a different potential.
Once again the XLR pin#1 is a shield it's not part of the audio circuit ground.

So...should I be using these cables and does this show that there is some problem internally with my sub,seeing that the hum drops down in level when using these xlr's? Thanks,Huck

[Huck]

What about using the 2 conductor with shield,with the shield,hooked to chassis ground,instead of pin#1(signal ground)?Thanks,Huck

[Speedskater]

But with a balanced analog interconnect, XLR pin#1 is not signal ground, it's chassis shield.
Or at least it should be, some manufactures choose to break the rules.  AES48

[adydula]

I have had 60 cycle hum in a subwoofer and changed out the electrolytic, just got old and dry.... it may be something in the circuitry is not built ie soldered well... maybe a cold joint in the filter cap area? Another possibility.

Also try at another friends house etc if you haven't already (didn't read all the posts).

Good luck

A.

[Huck]

My subwoofer was made in Italy,so maybe they wire their stuff differently? I dunno! Huck

[Phil A]

Apparently others have complained about hum:

http://en.audiofanzine.com/subwoofer/rcf/art-905-as/user_reviews/
“To be continued...

I'm back with a new post...

After a few hours one speaker produces AC noise at 50 Hz.

So I'll go back to the dealer to contact RCF's after sale service...

To be continued...

I'm back again: I just got the third speaker and it's a BIG DISAPPOINTMENT because the problem is worse than on the second speaker!

The 50Hz noise is actually louder and an additional hum can be heard. It's very strange for a subwoofer, isn't it?

I'll go back to the dealer.

I'm starting to lose my faith in RCF's quality control.”