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How to isolate turntable from footstep shake or vibration

Even while the Oracle turnable that I use has a built-in springs suspension by design there is a low or even sub-low frequency boom every time someone walks in a room. This becomes really bad with the subwoofer’s volume set high as the low frequency footsteps make straight to subwoofer where they are amplified shaking everything around. It seems the cartridge is picking up the footsteps very efficiently as even a lightest foot down becomes audioable. What can be done to attempt to isolate the turntable from the low frequency vibrations? Interesting, that the lower the volume of the subwoofer, the less the footstep shake is evident and with the subwoofer turned off it is a barely a problem at all. 
esputnix

Showing 4 responses by cleeds

cleeds
6,067 posts
 
mijostyn
... Unfiltered the subwoofers will gladly try to reproduce this. They are not projecting any "sound" into the room. They are no where near large enough to produce those frequencies but, if there is an electrical signal at 8 Hz they will gladly flap around at 8 Hz adding distortion to the sound you want to hear ...
I can assure you that your LPs have no electrical signal at 8 hZ. You obviously have a rumble issue and use essentially a rumble filter to resolve it. That works!
cleeds
6,067 posts
 
mijostyn
@cleeds , that is right, flat to 20 hz at 1 meter. There is no full range loudspeaker I know of capable of reproducing the bottom two octaves in your average room at realistic levels ...
You obviously never heard an Infinity IRS Beta system. Essentially flat in my room to below 20 hZ. No Band-Aid "rumble filter" or heroic digital DSP required.
cleeds
6,067 posts
 
mijostyn
@cleeds , you obviously have no experience with powerful subwoofers and turntables ...
You’re half-right - I don’t use powerful subwoofers. I use a full-range speaker system that is essentially flat in-room to below 20 hZ.
The problem is not the turntable. It could not be happier. The problem is the subwoofers trying to reproduce every little irregularity on the record causing the woofers to make long excursions. If I turn the volume up loud enough I can get the voice coils to hit their stops making a very painful sound.
That sure sounds like a problem to me. I want my woofers to reproduce what’s on the LP, unfiltered. If you’re getting "irregularities" that cause "long excursions," then it sounds like you have arm/cartridge resonance problems. Those can usually be resolved without relying on rumble filter Band-Aids but - as I said - rumble filters do work. It’s fine if you like them.
cleeds
6,067 posts
 
mijostyn
... It means that vibration is getting to the sub chassis in spite of the suspension either through a poorly designed suspension or directly vibrating the sub chassis ...
Not necessarily. If this is an Oracle Delphi (the OP doesn't say what model Oracle he has), then setup is even more critical than with many turntables. Its springs need to be individually rotated within the suspension towers so that the entire suspension functions pistonically. It is a very tricky adjustment to get right and it also drifts over time, requiring readjustment. It's a nuisance - and part of why I sold my Delphi way back when - and the table won't perform well if it's not properly setup.
It is very important to use a subsonic filter and digital filtering is the only way you can do this effectively without injuring the bass. I roll off at 18 Hz 80 dB/oct. I use a Sota and a large subwoofer array and have absolutely no issues.
Subsonic ("rumble") filters are a Band-Aid so if you use them you already know you have issues. They certainly can be effective, but I think the best solution is to remedy the problem at the source. It can be done - my system is essentially flat in-room to below 20 hZ. That's spooky bass with no rumble and no rumble filter.
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