Hot Water posted:SPSF posted:Not opinion. If you cannot distinguish between the two, you are tone deaf. I have photographed just about ALL Santa Fe SD40, SD45, SD45-2, F45, FP45 and remember when the GP60 came out it had a Different sound. It wasn't in my head, It is a different sound. I saw these both at idle and accelerating.
Tell me that these sound the same:
https://www.youtube.com/watch?v=lavPKAsDlp4
https://www.youtube.com/watch?v=dViB5ckrRdEYou are trying to compare sounds of a 40/45 series units, without exhaust silencers, to Dash-2 series units WITH exhaust silencers, to a 710 with a different/larger exhaust silencer. Not to mention the fact that earlier EMD units equipped with 645 engines had much higher idle speeds, than the later Dash-2 series units, and then finally the 710 engines with the VERY low idle speed.
When comparing the full load exhaust sound of any Dash-2 series unit (with exhaust silencer) to the full load exhaust sound of the 710 equipped units (again with exhaust silencer), they all sound pretty much the same.
On the other hand, I may very well be "tone deaf", after more than 40 years of diesel and steam locomotive exhausts! That said, comparing them at idle is a waste of time, in my opinion, as there are way too many designs differences.
I think if this is the biggest issue with these, then we can safely say lionel did a GREAT job on them 
