Hot Rods Exhaust systems on a 1940 Chevy

I just got my exhaust system installed on my 1940 Chevy coupe. I have 2 1/4 pipe and some flow tech mufflers. The type were the Terminators. They have 3 different types. The motor must not have alot of compression as the system is not loud. I have some large tips and an "H" pipe. Is this the reason it is not loud? Don't get me wrong I don't want alot of noise however the sound is moderate. Whats the best system for a street rod.

 

What makes the exhaust system have a deep thoaty sound?