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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 say it's not audible I mean the woofers are pumping but I don't hear any thumping in my ears, the way I do if the subwoofer is on. Yes, it is definitely being driven by the amp and using up some power but it doesn't audibly interfear with the music.

The sub has a substantially bigger driver which moves more air and is designed to pump out those low frequencies. I hear the "whump" from the sub.

So based on my experience with thicker records vs flimsy vinyl I definitely see less of a problem with the thicker records. So I am leaning toward the belief that it's on the records and my system is resolving enough to bring out the flaws in the medium. Again, this was not as much of an issue before I got a better phonostage.

All in all, again, turning off the sub seems to resolve the worst of this to my ears and, short of building a subsonic filter, is the solution I'm going with for now. None of the mechanical solutions I've tried seems to make any difference at all.

On another note, I have been playing with string recently in place of the rubber VPI belt and have noticed a nice improvement overall. Yes, I have a speed controller and it is essential to getting this right. No, it doesn't change the subsonic issues.

Happy New Year,
Bob
koegz
317 posts
 
disconect sub i agree. thickness of the vinyl, no way. i have some 2000 vinyl albums of all thicknesses and age. rarely does newer thick vinyl sound better then the original ussally thinner vinyl. there is little doubt in my mind that the main problem is your tt. i do not know where you live but bring me that vinyl and i will prove it. (voorhees nj)
ptmconsulting OP
1,000 posts
 
Just wondering ... the VPI platter is not supposed to be used with a record mat. It's design is intended to couple the record to the "vinyl like" composite platter.

What would a record mat do for me here? Might it help dampen these vibrations? What do they do for the sound (I would expect a dampening there as well, no)?

Any thoughts? Any recommendations on which ones to try? Anyone with practical experience using a mat on a VPI platter?

Thanks,
Bob
mapman's avatar
mapman
22,550 posts
 
There is no doubt that thinner vinyl is more susceptible to warping and that warped records will result in subsonic noise that can cause a subwoofer driver to pump wildly if transmitted and not filtered somehow. A cartridge with lower compliance stylus might be more immune to the problem, but the best solution is to replace the record with a better copy when this occurs (or get a good digital copy if not allergic to digital).
acoustat6
357 posts
 
Markpao said "I just received a pair of those 20hz FMOD RCA filters."

Did this help with your subsonic problem? Does it sound OK? Are you using them? Do you recommend them?

Bob
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