Why do my bass drivers shake violently listening to vinyl

OP chat w Rutan….and as I recall RV is visiting him…today ? Jim

You won’t see the woofers dancing if they are in an enclosure that constrains motion at subsonic frequencies. You also won’t see them dancing if the preamplifier or amplifier in the upstream chain cannot pass subsonic frequencies, e.g., if you use a transformer coupled tube amplifier or if you have engaged a subsonic filter on your preamplifier. In either of those two cases, the woofers are protected from damage AND you won’t experience the audio distortion associated with the woofer dance. However, if rumble is present due to some sort of feedback (acoustic mechanical or electrical) at the source, these palliative measures do not prevent or cure it. In any system, the presence of rumble does not always cause the woofer dance. Audionoobie, if you have done the experiment of borrowing another TT to see whether the problem persists, and if the problem does persist, then I give up,... you need a rumble/subsonic filter, best inserted between your phono stage and your linestage.

I was experiencing very noticeable noise from my Technics SP-1000R table. Mostly an echo type reverberation when walking near the table etc. Tapping on the stand or plinth was like playing a drum. Ordered the Insolation feet from this shop for it and I just screwed them in. An immediately noticeable silence. Going to listen to a few records to make sure it hasn't killed the sound completely, but as far as decoupling goes they're awesome.

It is the nature of the vinyl format to have this rumble.

This statement is misleading. The LP itself should be quite free of rumble.

I purchased the KAB rumble filter.

@audionoobie It sounds to me as if you have a mismatch between the arm and cartridge.

My woofers at home are 15" and the speakers are flat to 20Hz. I never have problems with the woofers flopping about. But I am careful to make sure the cartridge isn’t too compliant for the mass of the arm. If it is, as the cartridge negotiates the minor ups and downs of the LP surface, the mass of the arm will take more time to catch up with the cartridge. This causes a lot of low frequency output from the cartridge and its stuff that isn’t on the LP surface.

You can either reduce the mass of the tonearm or decrease the compliance of the cartridge. The former might be done by replacing hardware holding the cartridge in place (or going with a lighter cartridge); the latter is done by replacing the cartridge.

If you have the cartridge/arm combo right, your electronics can have bandwidth down to 1 or 2Hz and you’ll have no troubles with your woofers.

The introduction of the rumble filter will have an audible consequence (depending on how well your speakers play bass); by introducing phase shift, there will be a loss of bass impact. Its better if you can get the arm/cartridge combo correct.

 

My woofers at home are 15" and the speakers are flat to 20Hz. I never have problems with the woofers flopping about. But I am careful to make sure the cartridge isn’t too compliant for the mass of the arm. If it is, as the cartridge negotiates the minor ups and downs of the LP surface, the mass of the arm will take more time to catch up with the cartridge. This causes a lot of low frequency output from the cartridge and its stuff that isn’t on the LP surface.

You can either reduce the mass of the tonearm or decrease the compliance of the cartridge. The former might be done by replacing hardware holding the cartridge in place (or going with a lighter cartridge); the latter is done by replacing the cartridge.

Is this part of the logic behind the Dynavector dv507 arm having a pivot configuration which minimizes vertical moving mass?

Isolation issues can also greatly impact woofer flapping. I had occasional problems when I was using a poor Lovan rack (stackable modules, not very rigid). They completely went away with an upgrade to CMS Maxxum - still using the same kind of table, speakers, cartridge, arm, amps, same positioning, etc.

15" Tannoy drivers here so when the woofers flap at all it is VERY easy to see. Floor here is suspended wood, but old world commercial construction - not nearly as compliant as modern residential suspended floors. Still not like a concrete slab either, though.