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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
acoustat6
357 posts
 
Hi Bob, I agree, I too have some lps that have lots of low freq abberations (rumble and high levels of 20hz and below noise) and others I play are "close to perfect", very little rumble but the 20hz and down "noise" is there no matter what. This is the first thing you should address, as it does give your amp fits and also, even if you do not hear it it is screwing up your speakers sound trying to reproduce it.

Yes, if it is your setup it would be there regardless of the LP. You said subsonic pumping is almost gone with these LPs, what I believe you meant to say or are heaing is rumble (above 20hz). Correct me if you disagree. It can always sound better:)

My thought is that one can live with the rumble especially if ones system is down a a few DBs in the lower freq, but a 20hz filter will be of benefit to any system.

Bob
markpao
524 posts
 
I just received a pair of those 20hz FMOD RCA filters. Does it matter where I connect them into my system? My TT is connected directly into my pre amp. I'll post my results.
eldartford
4,262 posts
 
Put them at the preamp output. They are intended to be used with a "line level" signal. Better yet, if your preamp has a TAPE interface, put them there with a short interconnect. Then you can easily compare with/without results.
koegz
317 posts
 
Ptmconsulting; i am confused, are you talking about cone movement on your sub or your speakers?
ptmconsulting OP
1,000 posts
 
There is cone movement on both. It is not audible on my speakers (which go down to about 30Hz I would guess, but due to the slope is probably still putting out into the 20's but at a lower level). The pumping on the subwoofer is noticeably greater and sometimes very audible. You can hear it by ear, like a whoomp-whoomp air pressure feeling.

I've tried several different methods of reducing resonance to see if that would improve things. Adding mass to the headshell, damping the tonearm, taking the table off the rack and putting it directly on the concrete floor, etc. There is no noticeable difference from any of them, so I think it is subsonics fromnt he record itself in my case.
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