I second Elizabeth's comments. Although your statement that the cable type you modified is the same cable type as the one that was factory terminated with XLR's would seem to imply that the cable you modified has two signal conductors plus a separate shield or other ground conductor, and it would therefore be suitable to use.
Given that, and assuming you've compared the two sets of cables at the same location in the system, the volume difference is almost certainly 6 db, and the cause would be either an open (missing) connection on one of the pins, or a short between one of the two signal pins (pin 2 or pin 3) and ground (pin 1). A multimeter would allow you to quickly determine which of those possibilities is occurring.
Regards,
-- Al
Given that, and assuming you've compared the two sets of cables at the same location in the system, the volume difference is almost certainly 6 db, and the cause would be either an open (missing) connection on one of the pins, or a short between one of the two signal pins (pin 2 or pin 3) and ground (pin 1). A multimeter would allow you to quickly determine which of those possibilities is occurring.
Regards,
-- Al