Headshells, though, are a lot more complex than a simple pipe or wand. While we have some hunches (i.e. almost all of them ring at about 9-13kHz), it is impossible to truly separate the headshell's performance from that of a tonearm while the headshell remains attached.
To isolate the headshell, we have improvised the rig out of an old drill press chassis. The headshell is held by a standard SME/JIS bayonet connector which, in its turn, is gripped tight by a vise. But, obviously, this makes signal pickup from a rotating disc impossible.
In an ideal world, we would have access to a broad-spectrum vibration platform like the one used to calibrate accelerometers
. It could easily be used to excite the cartridge stylus, and we will get a picture of vibrations that would be identical to using a real LP. Sadly, we don't have one, and even renting something like this is prohibitively expensive.
However, there is a very simple and cost-effective way of doing broadband excitation. It's called IET — Impulse Excitation Technique
Instead of using a broadband shaker, we'll be striking the device under test with a very small calibrated hammer. The resulting impulse response can be then analyzed to yield resonant modes and damping estimation.