Tonearm Resonance

A few months ago I found how easy it is to use Audacity to analyse the frequency spectrum of a recording. I wondered whether using this tool I might be able to 'see' the difference in recordings between an original and remaster, just as a matter of fun. I started with a track that I have in original and remastered vinyl, Led Zep II. It's easy to generate spectrum plots, as below.

Original

Remaster

It might not be easy to see here but an 'old school' comparison by printing and overlaying the two plots does show clear differences, particularly over 6MHz. Ref to Graham's question about the aged hearing of the mixer?

Taking it a bit further, I wondered how different the vinyl would be to a different format, cd or streaming.  The same remastered track selection from Qobuz  is remarkably similar to the vinyl

Qobuz

Except for the big lump below 30Hz on the vinyl!.  This got me thinking and researching before 'discovering' I'm actually measuring the tonearm resonance. A simple and pretty accurate process.  With more research I learnt more about the relationship between cartridge compliance, weight and tonearm characteristics.  All wisdom suggested to resonance should be between 8-12Hz although some expand this to 6-14Hz as being OK. With this in mind I measured my other cartridges, most  (Technics EPC-205C and A&R P66) came out as 8Hz but my prefered Victor U-2 measured 6.5Hz. Does this make any real difference?  I couldn't see a way to alter the resonance frequency but found suggestions that a fluid damper (KAB  for my Technics deck) can lower the resonance amplitude. In for a penny...I thought I might try one, everyone says they are beneficial. The result from the spectrum plot showed a small reduction on amplitude of 3dB ( I.e. resonance hump 12dB lower than 60Hz peak whereas before it was 9dB lower).  So a reduction but not massive improvement, although there are other benefits.

Remaster with KAB Damper

Anyway, the basis point of this long post is to question whether the tonearm resonance causes harm. It's below any audible frequency. I don't see any speaker (or sub) trying to reproduce such low frequency but is the amp wasting power (energy) handling these frequencies? Would it be better to have a high pass filter at 20Hz to remove the rumble?

As I say, sometimes learning just highlights one's lack of knowledge.