Seemingly rock solid understanding of dimmer doubling shaken by current show

Maybe this will help:

Ion uses an offset of 256 for the doubled dimmer when using DMX addressing, and an offset of 20,000 when using sACN, EDMX.  As long as the address the Ion uses for the dimmer agrees with the rack then all is good. For most purposes it does not matter since Ion will route the information out all the ports that have been enabled.

Given dimmer 1 in DMX universe 1 is doubled, the second part of that dimmer can be referenced by address in a number of ways:

• 1B (base + offset)
• 257 (absolute DMX)
• 1/1B (explicit universe, base + offset)
• 1/257 (explicit universe)
• 20001 (sACN/EDMX)
• 1/20001 (explicit universe)

Some of the above are better to use than others. My preference is to call it 1B or 1/1B and let the console work out the absolute address, and which port(s) to send

Maybe this will help:

Ion uses an offset of 256 for the doubled dimmer when using DMX addressing, and an offset of 20,000 when using sACN, EDMX.  As long as the address the Ion uses for the dimmer agrees with the rack then all is good. For most purposes it does not matter since Ion will route the information out all the ports that have been enabled.

Given dimmer 1 in DMX universe 1 is doubled, the second part of that dimmer can be referenced by address in a number of ways:

• 1B (base + offset)
• 257 (absolute DMX)
• 1/1B (explicit universe, base + offset)
• 1/257 (explicit universe)
• 20001 (sACN/EDMX)
• 1/20001 (explicit universe)

Some of the above are better to use than others. My preference is to call it 1B or 1/1B and let the console work out the absolute address, and which port(s) to send

Eos/Ion/Element have a setup option of a user configurable dimmer double offset which is applied to the patched addresses.  The default dimmer double offset is 20,000 on the console, which matches the default offset when doubling a port on a Net2 node, a Net3 gateway in Net2 mode, or a networked CEM+.

Assuming a default system, if you dimmer double address 1 on your console, it will output EDMX 1 for address 1A and EDMX 20,001 for address 1B.  An EDMX port on a network node configured to start at EDMX 1 and dimmer doubled will output EDMX 1 as DMX Channel 1 and EDMX 20,001 as DMX Channel 257.

sk8rs_dad is correct that there are several different ways to reference each of these addresses on the console. 

The A side can be referenced as:

• 1 (absolute address)
• 1A (absolute address with doubling)
• 1/1 (universe notation)
• 1/1A (universe notation with doubling)

The B side can be referenced as:

• 20001 (absolute address with dimmer double offset manually added)
• 40/33 (universe notation with dimmer double offset manually added [20,000 addresses = 39 universes and 32 addresses])
• 1B (absolute address with doubling)
• 1/1B (universe notation with doubling)

If you play around in patch on your console, you will notice the addresses for each side are mutually exclusive.  If you patch address 1/1B and then try to patch address 40/33 you will be prompted that the address is already in use.   That's because they're all really the same address and you can only patch an address to a single channel.

Generally speaking:

• On a pure network system you'll want the console default dimmer double offset of 20000 unless someone has done some custom configuration. 
• On a system using DMX out of the back of the desk to a doubling Sensor rack, you'll want to set your dimmer double offset to 256 so you can get the B sides out of the same DMX port as the A sides. 
• On a mixed network and hard line DMX system (all going to Sensor racks that are doubling), the best answer for you may vary. 

If in doubt, give a call to your local ETC Tech Service office and we'll be happy to help you find the right solution for your system.