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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

Showing 9 responses by eldartford

eldartford
4,262 posts
 
Most rumble is from vertical groove modulation. Horizontal modulation, which is a mono signal is much cleaner. A good rumble filter will blend the LF signal to mono, which many people do anyway when they connect a single subwoofer. Also, when records are cut the LF is often blended to mono right on the LP so that less-than-audiophile cartridges can stay in the groove. If the LP has been made this way all the LF you are getting off it in stereo is rumble.

Many LPs have rumble cut into the grooves and no amount of vibration isolation will help. Particularly in older recordings the air conditioning systems of recording halls were a big cause of rumble. It went unnoticed until newer playback systems with extended LF response came into being.
eldartford
4,262 posts
 
Dan_ed and Fap...I am a strong proponent of multiple subs, but when playing LPs I have found summing of LF to be essential. Of course you can make a rumble filter which simply attenuates all LF, but why throw away the mono component which is relatively rumble-free?
eldartford
4,262 posts
 
Acoustat6...What you describe is ideal. All we could quibble about is the frequencies.
eldartford
4,262 posts
 
Rumble, due to turntable vibration or recorded in the vinyl has always been my second gripe about LPs, the first being HF surface noise. CDs have taken care of this problem.

Imagine my surprise to get a CD of theatre organ music (from Organ Stop Pizza, in Mesa AZ) which has what seems to be lots of LF noise. It took me a few plays to realize that this sound is exactly what you hear in the hall as you eat your pizza and drink your beer. It's the organ's air generation machinery. Once you realize that it is not a recording deficiency it ceases to be an annoyance.

In a similar vein, surface noise does not bother me when I play my LPs of Benny Goodman's 1938 broadcast recordings. Somehow it becomes part of that particular musical experience.
eldartford
4,262 posts
 
Ptmconsulting... Your "beautiful analogue signal" has probably been generated out of a digital mixing consile :-(
eldartford
4,262 posts
 
The pumping woofer does not just use up available amplifier power. It gives rise to "Dopler distortion" because the advancing and retreating cone is also reproducing higher frequencies, which are modulated by the cone movement.

Get a rumble filter. Cheap and easy.
eldartford
4,262 posts
 
Mapman...A passive rumble filter would require large and expensive inductors and capacitors. And lots of them to yield the minimal 18 dB slope. Rumble filters are only practical for line level signals.
eldartford
4,262 posts
 
Put them at the preamp output. They are intended to be used with a "line level" signal. Better yet, if your preamp has a TAPE interface, put them there with a short interconnect. Then you can easily compare with/without results.
eldartford
4,262 posts
 
I don't know if anyone has suggested this yet, but try switching your system to Mono. If the preamp doesn't have a Mono switch, invest a couple of bucks in a Y-adapter interconnect at radio shack. If this cures your problem, as I suspect it will, you need a rumble filter that mixes channels below some frequency higher than 20 Hz. (The Y-adapter mixes at all frequencies).
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