The arithmetic difference between the cut-off frequencies or – 3 dB points in a response curve, expressed in octaves or as a frequency difference in Hertz.
"Oh my goodness! I am so very pleased with the CD you made me from my old Jose Melis LP album. I had lost hope of ever listening to these songs again, since apparently the album has never been made into a CD, and I don't have a turntable anymore. I wasn't even sure if the LP was in good enough condition to work with, (I think it's about 30 years ..."