[turf3]

At one time I had a 12M with these, and a friend had an almost identical 12M with flat metal (I think). Using the same mouthpiece I really couldn't tell a lick of difference.

 

[turf3]

Interesting, were the sizes of both horns' resonators "exactly" the same ? Mine as you see were huge compared to the pad size which I think made a large difference essentially I am playing on metal pads (someone correct me if I may be off on that)

If you're asking me about the two 12Ms, I have no idea about the sizes, this was over 20 years ago. I'd expect they were similar in size.