Vinyl Asylum: Arm/Cartridge Resonance by John Elison

I recently reinstalled my AT-OC9ML/II and decided to measure Arm/Cartridge Resonance using the Hi-Fi News Test Record. Actually, I decided to record the tests and transfer them into my computer so I could look at the waveforms in Sound Forge. By doing this, I discovered something very interesting. The voice announcements do not represent the actual frequencies very accurately.

I also discovered that my AT-OC9ML/II mounted in my SME V tonearm has a vertical resonance of 9-Hz and a lateral resonance of 7-Hz. These are considerably different that I previously thought from using the frequency voice announcements. This means that my cartridge has a compliance of about 16-mm/N based on a 10.5-g effective mass tonearm and a 9-g cartridge including mounting screws.

To give you an example of just how inaccurate the voice announcements on the Hi-Fi News test record are, I measured the frequencies visually in Sound Forge and compiled a table below. I adjusted the speed of my turntable very accurately by timing revolutions of the platter so that its speed was accurate to between 0% and 0.04% fast. I made absolutely certain it was not going even the least bit slow. Be advised, this is the old Hi-Fi News test record. I donâ€™t know if the new one is any better. Perhaps someone who owns one can make some measurements.

Best regards,
John Elison

PS. I couldn't measure the lowest frequencies because a cartridge will not respond to frequencies below its resonance frequency.