There appears to be a mistake in the Ultra-X12 PDF manual. On page 12 when it talks about setting up Max Extension VS Max Output. Here is the Quote from the manual.

"When using the MAX EXTENSION mode, make sure to
tightly insert the provided Port Plug into one of the ports
located on the bottom of the subwoofer. In MAX EXTEN
-SION mode, both ports must remain open."

I believe that the last line should read "In MAX Output mode, both ports must remain open." Because the following paragraph says
"CAUTION: Do not leave both ports open when the PORT MODE switch is in the MAX EXTENSION position as your subwoofer's performance will be compromised. If neither of the ports are blocked with the supplied Port Plug, the PORT MODE switch must remain in MAX OUTPUT mode. Failure to adhere to these requirements can lead to poor performance and damage to your subwoofer"

It is a little confusing. Someone might want to correct this, so someone doesn't accidentally damage their Sub.

Thanks