Short Answer:
Yes.
Longer Answer:
Each additionally requested file adds (so called overhead):
- A DNS Lookup - if the DN is not already cached
- A TCP Handshake
- A HTTP Request itself
and only then the real download of the file begins.
So by concatinating you could save these factors - which would add up on many files.
Just today I watched an interesting talk by Paul Irish exactly about this, I recommend you watch it: "Delivering the goods"
To quote one of his slides:
Most of the HTTP data flows consist of small, bursty data transfers, whereas TCP is optimized for long-lived connections and bulk data transfers. Network roundtrip time is the limiting factor in TCP throughput and performance in most cases.
Consequently, latency is the performance bottleneck for HTTP and most of the web.
Also you have to consider, that not every browser loads as many files in parallel like chrome. I found an SO-Post about how many connections the browser does in parallel (from 2013).