Reposted from PSR forum....

"I asked Bose if only one extention can be used for my Compact L1....

This is the reply from Bose.....

We made the decision to be specific in the manual by stating that both extensions must be used when the system is used in its extended position. It is our belief that this provides the best sound quality for the majority of extended use applications.

Using only one extension will not harm your system but is not generally recommended.

Thanks
Neil from Bose"