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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
 
There is cone movement on both. It is not audible on my speakers (which go down to about 30Hz I would guess, but due to the slope is probably still putting out into the 20's but at a lower level). The pumping on the subwoofer is noticeably greater and sometimes very audible. You can hear it by ear, like a whoomp-whoomp air pressure feeling.

I've tried several different methods of reducing resonance to see if that would improve things. Adding mass to the headshell, damping the tonearm, taking the table off the rack and putting it directly on the concrete floor, etc. There is no noticeable difference from any of them, so I think it is subsonics fromnt he record itself in my case.
acoustat6
357 posts
 
Hi Bob#1, you said, "It is not audible on my speakers (which go down to about 30Hz I would guess, but due to the slope is probably still putting out into the 20's but at a lower level). The pumping on the....

Not to be argumenative or anything, but when you said "it is not audible", do you think your speakers can move without making sound or using power from your amps.... just something to think about.

I do think you are going in the right direction:)

Bob#2
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
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