Subsonic Rumble Solutions

Hi Bob, you could try these;

http://store.hlabs.com/pk4/store.pl?section=12

They are only $30 and would give you an idea of what would happen if you implemented a subsonic filter. I dont know the quality of the units or how they would sound. But it would give you a feel for a subsonic filter and an indication of what one would do for your system.

Please feel free to experiment with you tt/arm/cartridge and let me know if you come up with something that you think I should try.

Bob.

Hey, those little RCA "Sub Sonic Filter pairs" looks cool, and may well be worth trying out for only $29.

There are 2 values: 20Hz and 30Hz. Both have a 12db slope to them - not very steep. So if I was looking for 3db down at 17Hz then the best choice would be the 30hZ ones, right? I mean, down that low on the scale a 12db per octave slope goes very slowly down.

I found a chart with note values on it, but it only goes to 27hZ: http://www.phys.unsw.edu.au/jw/notes.html

Bob

Well, late for the discussion, as always.
It looks I'm having the same problem with my TT- woofers and even midrange driver pumping, start. with the lead in groove.
Subsonic filter aside for now, where do I start?
Cartridge?, TT support?, mat? subwoofer?

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.