Client has 6 B&O speakers, all plug into wall, powered, all have RCA inputs. I am completely thinking line level in. Four in the family room run off line outs on an Integra AVR. BUT, two in his office (Beolab 6000) have real B&O cables with the 2 prong DIN connector on one end, thru the attic and down to an RCA plug at the speaker end. The amp end is adapted to speaker wires off Denon AVR speaker outs and operates normally. How can this work?

A line level input driven by speaker outputs will distort horribly, and you will only have about the first 20% of the volume control range on the receiver. Not so in this case. Does The B&O speaker have some sort of magical circuitry inside that senses a line level versus a speaker level?

Perhaps there's a line-level converter somewhere in there. ???

I've had to make up adjustable line level converters in the past to run speakers off a decent amp that is fed by the speaker output of a B&O multi room system. Can't remember the B&O model at this point. I remember the adjustability being important though to get the output vs distortion ratio right. I had tried a couple of resistors but eventually found it much easier to just put in a pot and have a play with it.

You'll need a Z-Coupler or a resistor network at the BL-6000 end.

Here is some documentation.

2-pin DIN is always speaker level. It's easy enough to hide a Z-Coupler in an RCA plug. Measure the resistance of your "cable" from both ends first with the remote end open circuit, then shorted. If there is a Z-coupler in there, you'll be able to discover it.

I've forgotten the internal details of the BL-6000, but many of their speakers had printed circuit traces for built-in attenuaters. I would pop them open, remove a jumper and insert a pair of resistors.

This is very helpful. So you are saying the speakers had provision for attenuators? So if the existing Denon drove these normally, it is possible the attenuators are in place? Thank you.