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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
 
When I built it I was told that Corian is dense and fairly inert. It certainly is heavy (and pretty to look at), but I often question the same thing as you. I have toyed with the idea of applying a heavy piece of aluminum or some such to its bottom as an additional damping solution. But I have trouble trying to figure out how to attach it sufficiently and whether I should put some EAR Isodamp or some such between it and the Corian (e.g. constrained layer damping of sorts).

Bob
fap
32 posts
 
Hi Bob, yes circuit boards are available for the circuit, but all components need to be sourced by the constructor. All parts are easily available from the usual parts shops.

The filter input is connected to the output of the phono stage. I also use the Elliott Sound Products P06 phono stage which actually has an extended low frequency end. The P99 filter cleans up all unwanted cone movement due to warps etc completely. 18 Hz is where my filter starts operating.

As the amp is no longer trying to reproduce all the unwanted subsonic rubbish, there is more power available for the real music! Regards, Fap.
fap
32 posts
 
Bob, oh I forgot to mention I've noticed no audio degradation to any aspect of the audio quality with the use of the subsonic filter.

I was worried about that possibility, but it hasn't happened. I'm happy! Also there no no gain through the filter. The filter circuit is set for 'unity' gain. Regards, Fap.
shadorne's avatar
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shadorne
7,333 posts
 
I suspect you are not able to 'dampen' the vibrations from the wood block or corion table. Squash balls was the right idea. Spikes are a bad idea. Personally I'd try memory foam next or a different sized wood block and platter - to me they both look too thin and both would necessarily tend to vibrate/flex in the vertical plane over their surface.
dan_ed
2,451 posts
 
Of course you guys know that you could also do the filtering between the pre and the amp. I'm beginning to think about trying this sometime for exactly the reason Fap pointed out. If you cut those unwanted frequencies out so that the amp and driver doesn't have to work on trying to reach those lowest regions, it should clean up the bass. Hey, it works on the other drivers up the spectrum.
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