Hi Katalyst, I looked at the "Optimal M15" file that you uploaded. I'm quite sure it was corrupted ( or else the file that I uploaded was corrupted somewhere along the way ) . - I say this because the un-filtered response was very skewed//distorted. Anyways; here's what the raw Horn/Driver looks like ( before & ) after M15 filtering is applied ( at the noted optimal settings ) . I've uploaded the raw .frd file ( renamed as .txt file >> so just remove that additional extension before using it in XSim ) I looked at the .zma file ( enclosed within the XSim file ) and it wasn't corrupted, so I haven't attached it .