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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
maril555
619 posts
 
Mapman,
Thanks for your response. Yes, it is DD table, and I use Isoplat mat with cork backing. Driver pumping seems to happen only with the record playing, and with all types of record. As soon, as I lift up the tonearm, it stops.
Could that be an issue with the cartrige compliance mismatch with the arm? I have Shelter 501 MK II on silicone damped Technics arm.
Also stock Technics feet are replaced with Audiopoints.
ptmconsulting OP
1,000 posts
 
There's been a lot of talk about rumble and subsonics. How does one differ from the other?

Another question about these little RCA filters - anyone guess what's inside them? They are sooo small there can't be much. The rest of the signal runs through them too, so I am concerned a bit.

BTW - I tried something a little different today. I think by now you've all heard of the Cartridge Man's isolator:

http://www.thecartridgeman.com/isolator.htm

I never liked the idea that it was squichy and compliant. Some time ago I tried putting a thin piece of EAR Isodamp between my cartridge and headshell and thought I noticed a difference. But I pulled it out again. Well this morning I put it back in and I can say that I think this makes a nice improvement in soundstage and smoothness of sound (Yes, I adjusted the balance and VTA afterwards).

Unfortunately it didn't cure any low frequency aberrations, but I do think it is going to stay. The good news (and you didn't hear it from me) is that you can contact EAR and they will send you free samples of Isodamp. It also works well under your motor as a vibration damping aid, or under any transformer in a power supply.

Enjoy,
Bob
mapman's avatar
mapman
22,664 posts
 
Maril,

I notice in your pic that the table sits close in from of on of the speakers. That may be a challenging location unless the floor in your listening room is extremely rigid, like a concrete foundation or such and same true for your stand.

If you can as a test , you might try locating the table behind the speakers for better isolation.

Unfiltered, on most good systems, most records will produce some movement in the woof and possibly the mid-range as well depending because few if any records are cut perfectly or are perfectly flat resulting in low frequency noise.

Relocating the table better and using a record clamp might be two easy things to try to reduce the effect.

Visible driver movement is often associated with the specific record itself. In this case, the patterns and magnitude of movement will vary from record to record.

If the problem is due to vibrations from the table motor system being picked up, I would expect little variability in pattern and magnitude from record to record.

If motor vibration is the source, it would probably persist the same regardless of tt location and specific record playing and this may require servicing of some sort for the table to fix if possible.
acoustat6
357 posts
 
Bob#1 said, "There's been a lot of talk about rumble and subsonics. How does one differ from the other?"

Subsonics is below 20hz and rumble is out of phase info above 20hz that is usually diminished by 40-50hz, though some lps have rumble up to a much higher freq., perhaps up to 100hz and even higher? And some have very little.

I don't know what is in the little filters. There cannot be much. Perhaps you would like them better if the came in a 20 pound one foot square box with a ton of wires and capacitors and resitors and tubes and...:)

I think the point here though would be to try them just to see if it affects your problem in a posative manner. Perhaps knowing that the little filters are not the best in terms of sonics. But if they do the job as intended a higher quality filter would be in order.

On the other front I spoke with my brother last night on this subject and his suggestion was to look into cartridge/tonearm compliance. I will work on this and post my findings. He suggested, after doing some research and calculations, that I add weight to my tonearm to lower the current calculated resonance of 14hz to 11hz.

Bob
ptmconsulting OP
1,000 posts
 
I have a Dynavector 20X-H cartridge on a Moerch DP6 red dot tonearm. Supposedly the correct tonearm for this cartridge (gotta love a Moerch, since you can buy and change armwands to match the compliance of the cartridge).

I was listening yesterday and, although there was some cone movement in the sub and woofer drivers, it didn't interfere with the music at all. I think I'm leaning more toward living with it than putting something else into the signal path that might negatively impact the rest of the sonic spectrum. Getting rid of this last little annoyance would not be worth compromizing any other part of the music.

Enjoy,
Bob
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