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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

Showing 5 responses by dan_ed

dan_ed
2,451 posts
 
My bass horns roll off pretty fast down in that subsonic region. They are down 6dB at 20Hz and drop pretty fast after that. Once you get down below 16Hz or so I would think that the system would begin to pick up resonances from the arm/cart. Who wants to listen to that? :-)
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.
dan_ed
2,451 posts
 
I wasn't that happy with the summing solution. Stereo subs have proven much better in my room. The bass is no longer boomy, LF details and directional clues are much better.

36 dB roll-off! That'll get the job done.

I'm curious about the phase issues mentioned on the page that Fab linked and wondered what some of you guys think. I was thinking of such a subsonic filter at the input of the sub's plate amp. My question regarding the low frequency phase variations with such a filter is this. If the mid-bass driver is feed by the line out of the sub's plate amp, would that alleviate any/most concerns about phasing?

Thanks
dan_ed
2,451 posts
 
Oh, great! Two Bob's. ;-)

Ptmconsulting, I think that at some point all you are left with is the groove thang and resonance from the table so there could be a need for an electronic solution for subsonics. I have my table sitting on two 1/4" aluminum plates that are bolted together. This plate sandwich is sitting on 3 Stillpoints. All of this is sitting on a 4" deep sandbox with granite shelf. Other than warped records I don't notice any problems.

But, as I said before, I am probably benefiting from the natural roll-off of my sub/bass horns. So maybe that answer's the other Bob's poll question. I don't think I need a sub filter at this point. Less is most always better, IMO.

However, I am open to trying it to see if I could benefit from using one. I'd probably shoot for a 16Hz cut-off.
dan_ed
2,451 posts
 
Bob #2 (I like that! :-)), that is the measured natural roll-off of the horns. To further complicate things there is a +6dB gain with having two subs, or so I am told. But your reasoning is still valid and does explain how different systems may need different solutions.
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