To slow hard drive or overloaded.

To slow hard drive or overloaded? Just 6 audiochannels (frozen) and ssd hard drive almost empty with 8gb ram. Why? Are able to play 10 seconds before everything stops! MacBook Pro late 2011. It all works on my 2013 iMac with 16 ram but there shouldn't bs any problem to work in the same projects on my macbook as long as we're talking about 6 audiochannels or should it?