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Subsonic Rumble Solutions

I know many of you have tried to address this issue. Short of buying or building a subsonic filter (that will/may negatively affect your transparency) - what methods reduce subsonics (meaning the pumping of woofers and subs when a record is playing)?

My system:
I have a DIY VPI Aries clone with a 1" thick Corian plinth, a Moerch DP6 tonearm and Dynavector 20X-H cartridge. This sits on a maple shelf. The shelf sits on squash balls. The balls sit on another maple board floating in a 3" deep sand box. All this on a rack spiked to a cement floor. The phono stage is a Hagerman Trumpet (no built in subsonic filter and very wide bandwidth). I use the 1 piece Delrin clamp on the TT. Yes, I clean records thoroughly and there are no obvious warps, especially after being clamped.

So my isolation is very good - no thumps or thwacks on the rack coming through the speakers. But if I turn the sub on I get that extra low end pumping on some records that hurts my ears. Mostly I leave the sub off when playing vinyl, but I would like to use it if possible.

There was some brief discussion of this on Albert Porter's system thread. I'm hoping to get more answers here.

So ... what methods have you tried to reduce subsonics that you have found effective?

Thanks,
Bob
ptmconsulting
ptmconsulting OP
1,000 posts
 
Just wondering ... the VPI platter is not supposed to be used with a record mat. It's design is intended to couple the record to the "vinyl like" composite platter.

What would a record mat do for me here? Might it help dampen these vibrations? What do they do for the sound (I would expect a dampening there as well, no)?

Any thoughts? Any recommendations on which ones to try? Anyone with practical experience using a mat on a VPI platter?

Thanks,
Bob
mapman's avatar
mapman
22,316 posts
 
There is no doubt that thinner vinyl is more susceptible to warping and that warped records will result in subsonic noise that can cause a subwoofer driver to pump wildly if transmitted and not filtered somehow. A cartridge with lower compliance stylus might be more immune to the problem, but the best solution is to replace the record with a better copy when this occurs (or get a good digital copy if not allergic to digital).
acoustat6
357 posts
 
Markpao said "I just received a pair of those 20hz FMOD RCA filters."

Did this help with your subsonic problem? Does it sound OK? Are you using them? Do you recommend them?

Bob
stevecham
3,340 posts
 
Too bad that more phono preamp manufacturers don't provide an option for such a subsonic filter. Does anyone know of a high end phono pre that has this feature built in and is switchable?
mapman's avatar
mapman
22,316 posts
 
Stevecham,

Probably because it would raise costs and even perhaps make the product less appealing to high end purists who do not like any extra circuitry mucking with their signals.

I do find also that it is less of a real problem with many higher power modern amps these days that have the guts to be able to handle the low frequency noise in most cases (decent record pressings) without clipping so there is little audible effect and lower risk of causing damage to the speaks.

I mostly listen on my OHMs where the driver is contained within a metal mesh cage so I can only listen for subsonic issues, not see them. I have to go to my more conventional Dynaudios if I want to look for a pumping woofer. Practically, it has not been an issue worth worrying about for me.
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