Hi David, thanks for your reply.
Only for monitoring, however, I am using a low spec external sound card (Behringer U control) to connect my active speakers. Could this be lowering the audio signal from core audio?
I have thought about purchasing NI Komplete audio 6 sound card, it has 24-bit 96/KHZ recording & 44.1, 48, 88.2, 96 kHz sample rate, I can not find the specs for the built own core audio to compare.