I have some old drivers that I am considering using. One is a very old cup midrange. I measured it using HOLM, and compared it with a more current driver at approximately 100 dB at 6 or 7 feet. The old mid is very flat, and has no breakup that I can see. The 3rd order distortion is roughly -50 dB. The newer driver is roughly -60 dB. Most of my listening is below 90 dB, so 100 dB would be the max for music for very short periods. (Maybe one song.) What are the odds that I could even hear a difference? I would think that 50 dB down would be inaudible.