GPIB string for Prologix USB-GPIB adapter

I have the misfortune to be working on a project with the wildly unpopular prologix USB-GPIB adapter.

I can communicate with an instrument through the prologix adapter by using the VISA string 

ASRL4::INSTR

and then prefacing commands with ++addr{GPIB address}\r\n

e.g. ++addr\s1\r\n*IDN?\r\n

Is there a way I can directly address the GPIB device so I don't need to preface every command with ++addr\s1

Having consulted (http://zone.ni.com/reference/en-XX/help/370131S-01/ni-visa/visaresourcesyntaxandexamples/) I have tried a lot of combinations with no success.  Any help would be appreciated.

Rgds,

Seán