Well, hate to burst the bubble but I don't think your carpet or pad had anything to do with the bass. It may have changed some other things--but not the bass. A 60 Hz wavelength is over 18 feet long. The quarter wavelength is nearly 5 feet long, which is how thick an absorber would need to be to attenuate it effectively. Anything below 1/8 of a wavelength and as a pure absorber it will not be effective. So, for the carpet and pad to make an appreciable difference at 60 Hz it would need to be between 2 1/2 feet and 5 feet thick.
I don't doubt that you perceive tighter bass, but I'll offer probably another reason for this. The bass hasn't changed appreciably--but other things have. The higher reflectivity and longer reverberation times from the dinning room have brought the mids and highs up. Now you have a better balance, and the bump that was bothersome before, is now not so noticeable. In fact, you may not have had a huge problem in the bass before, but just an over attenuated high frequency problem.
I'm glad it sounds better. It would have been interesting to measure frequency response and energy time curves before and after the changes. If anyone else is making changes like this--think about having measurements made. It could really help in improving your sound--and you'll know what direction to go and where the major diffeciencies lie.
