Subsonic Rumble Solutions

Hi Bob, I would most definatly go with the 20 hz filter, and I do believe 12db/octave cut is enough for you. Though my 20hz filter in the Marchand Basis is 18db/octave.

You do not want to start eliminating freq at 30hz. It is not necessary with todays great turntables and we DO want extension down to 20hz. Just not below it.

If the noise you are hearing is rumble, not subsonic, then a rumble filter is necessary. This is only necessary if you have stereo subs. Then you need to go to mono at a freq that eliminates most rumble which I believe (at least in my system) at 40hz. Some lps will still exhibit rumble above that freq, but they are far and few between and most is eliminated by the rumble filter at 40hz. A little higher is OK (up to 50hz, perhaps a tad higher). The Kab rumble filter which I believe was mentionend in this thread is set at 140hz. WAAAY to high, that is stereo there and includes voices instruments that would be mono'ed at 140hz and below, NO good.

With a 12db/octave 20hz filter you would be;
-12db at 0hz,
and -6db at 10hz,
and -3db at 15hz,
and -1.5db at 17.5hz.

With a 18db/octave 20hz filter (such as the one I employ) you would be;
-18db at 0hz
and -9db at 10hz,
and -4.5 at 15hz,
and -2.25 at 17hz.

A 30hz filter would get you -12db at 15hz and -6db at 22.5hz. You dont want that.


Bob

Maril555,

I'd start with the production quality of the record being played especially if the problem does not occur with the table running and no record playing or it is obviously variable from record to record.

If it is the table (is that a direct drive model?), maybe try a mat with better isolation.

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.

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

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.