Are subsonic filters important?

A phono cartridge with a compliant suspension and a tone arm with mass with have a ringing resonance in a subsonic frequency that will be excited by record surface irregularities (and record surface irregularities are ubiquitous, not just eccentricity and imperfectly flat surfaced -- which can also be partially improved with clamping, and record centering tables -- but not purely smooth surfaces). Oh, that if the ringing can cause mistracking too. There's no way around the mechanics of the mass/compliance situation (other than listening to CD instead). It's going to happen. It doesn't matter what stylus profile you use. It doesn't matter what arm or cart you use -- those will only determine the frequency at which the resonance will occur as a function of the mass and compliance. So then the question arises, how best to confront this inherent mechanical issue in LP playback. Fluid damping is one on solution (so was that little Shure brush). It's a mechanical problem inherent in vinyl playback. There are many such problems. They require mechanical solutions. The solution here is only going to be partial -- you're not going to eliminate the subsonic resonance, just reduce the time it rings, the width of its ringing and the amplitude of its ringing.

 

I respect the effort you put into your posts and into being a well respected member of this forum (as in you handle the fact that you are well regarded by more than a few responsibly)
that said, your posts are too long for me and I seldom read them
every engineer who ever lived says he knows best! : - )
I heard and understood where you're coming from the first time you said it and it's all good
I am aware of the schools of thought
I'm not going to change my mind based on anything you can say
so save yourself the effort with regard to my posts specifically, if they are in fact the impetus for your reply
I would like to be your "friend" as much so as is possible on an internet forum but I will never own an arm with fluid damping even if it were a gift
Peace
Michael

 

to be clear - I do understand that everything you said in post #149 is factually accurate (as well as obvious)
damping's just not how I want to roll
Michael

 

No, the shure stablizer and damping troughs are exactly mechanical damping solutions to damp subsonic resonance from mass-compliance in arm-cart systems. They're designed to address the inherent issue we're taking about, they're just different mechanical methods for addressing the problem. I can't imaging why this is even a vaugely controversial issue. This is basic, well understood stuff. The only place it seems to be controversial is on this forum.

 

I think that was the point. The post that responded to seemed to be suggesting if something was a good idea, all tonearms would implement it, which I didn’t really understand, either.

 

What is interesting is that a damper at the cartridge (Shure V15IV and V via the damped motion brush) is fundametally different to a damper at the pivot. The best method (which is true second order filter damping) is at the cartridge and dramatically reduces stylus scrubbing. A damper at the pivot is not formally second order damping.

However in Linear Audio Vol 10, pages 9-21 "The ins and outs of turntable dynamics - and how they mess up vinyl playback" he suggests that a combination of the brush and pivot damping together give the best control of the compliance/effective mass resonance and provides measurements to show this.

Since the damped brush patent by Shure is now defunct (patented 1981, plus 17 years) I'm really surprised that no other cartridge manufacturer has added this to their designs, or made a retrofit that attaches to the headshell.

 

I'll clarify the fist statement a bit. The brush damper acts between the source of the warps (the record) and the thing that produces the signal (the cartridge). A pivot fluid damper acts between the tonearm and the turntable baseplate. So their action is quite different.

 

Right, they don't work the same way, but they're mechanical solutions for an endemic mechanical issue in vinyl playback. What I'm surprised about in this thread is there seem to be a handful of people who seem almost downright hostile to the idea pretty basic idea that a) the problem exists; b) it effects what we hear; c) its a mechanical, not an electrical issue, and d) can be, has been and probably is best addressed mechanically -- reduce the resonance vs. filtering out some of its electrical effects after the fact (you won't be able to filter out any impact on tracking, or any modulation of the signal above the filter frequency).

 

The Townshend Rega damping device for Townshend turntables used fluid damping of the tone are at the cartridge end (but obviously still working on the arm, not in contact with the record). But it involved not only attaching a paddle to the Rega "headshell" but also swinging an oil trough across the record with every playback, so you could understand why consumers might think of something like that as cumbersome and potentially messy and unattractive. But I get that reasoning sure, and I'm not surprised to hear that measurements show that both kinds -- brush and fluid -- and both locations -- pivot and cartridge -- used together produce better results.

 

@chervokas, I´m sure You could make a fluid damper to the Rega arm. A little nice project.

 

You read different than I do. Let's try this again.

I have no opinion on them one way or another. I did comment that I am not a tonearm engineer.

As such I have neither recommended them nor I have I not recommended them.

From my own personal standpoint, I don't put anything in my system that I don't personally thing belongs there.

At this point, being completely satisfied with both on my non-damped Rega tonearms, I have no immediate desire to put a damper in my system.

Is a VTA adjustment important? some feel that is is, Rega apparently feels differently.

My comment still remains.

Show 'em how they should be doing things.

 

Again, admitting to be pretty much egnorant on the subject of tonearm damping I do feel that there can be more than one cause of subsonic "noise" that may present itself in a turntable based system.

You can have feedback issues causing mechanical vibration, caused by the room and lack of proper turntable isolation.

You can have vibrations caused by the motor and platter itself that are transmitted to the tonearm.

In both of these cases, I have not personally experienced any issues that appear to be audible in my system.

They both my indeed be present, but if I can't hear them, then they are not a concern to me.

It doesn't appear to be a concern to Rega, so I'm good with it.

Being of limited means myself and wanting at least a turntable of a certain quality (and at a price point that I find workable for me), I decided on a Rega RP6 with a white belt and upgraded groovetracer subplatter.

I do have a couple of Dual 1219's for a completely "vintage" system that I had intended to assemble.

But, I also have a fine, Vinyl Nirvana, vintage Thorens TD-160 Super that has been both restored and upgraded, including a Rega/Moth RB-202 arm that has been rewired with Cardas cable.

Both of these TT's have nice phono preamps, one SS and one tube.

This is what I have accomplished on my budget. With TT's, the "sky" is really the limit where you can go with it.

While there might be a $4k "gee-wiz" damped tonearm out there that may be better, it is something that I can live with. This is not different than the other decisions that I have made in assembling my systems. I prefer to refer to them as "decisions", rather than compromises.

But there is one thing that @Helom mentions and I totally agree with.

That being that at least some subsonic noise does originate in the grooves os some recordings.

Being that I don't visibly see woofer pumping with any but a very few records I have, I don't consider it a major concern.

But that also tells me, that the issues are not inherent in my system, because this is not an issue that is appearing on the other 98% (or so) of my other records.

This is telling me that there is subsonic noise present in the grooves on these certain records.

This noise is being directly transmitted to the stylus. From there it is traveling up the cantilever and this energy is being directly transferred into the coils by the magnets that are attached to the cantilever (I use MM cartridges).

At this point, the arm has not even come into the picture.

The coils are generating a signal from this sub-sonic energy, which is then being transferred into the system.

My impression is that this is going to occur, whether or not, the tonearm is damped or not.

This energy is originating in the record grooves and is transferred into the system before the tonearm even has any chance to attenuate it.

In this case, I don't really see any benefit of having a damped tonearm in the system.

Going to my above statement, a subsonic filter is not necessarily a band-aid, but a legitimate means of filtering out this type of subsonic noise.

The advantage here, is that it can be taken in and out of the system with a touch of a button.

This way, like with tone controls, it does not have to be present in the signal path, when it is not needed.

Seems like a good solution to a problem when you need it, like having a raincoat on hand.

Just my personal take...

 

There are many mechanical sources of noise in turntable playback, but fluid damping of the tonearm is designed to deal with a specific, unavoidable one -- the ringing of the arm/cart at a particular subsonic resonant frequency. There would be no problem with it if the ringing weren't excited by something. And it can be exciting by things like footfalls which tend to occur at aroubd 4 or 5 Hz. But you can keep footfalls from reaching the turntable by mounting the table on a wall shelf or using an iso suspension that isolates to such low frequencies. But when the record spinning itself is the source of the excitation, because of warps, off centeredness, and general imperfect flatness of the surface then it needs to be damped at the source. Fluid damping acts like a shock absorber for that low frequency movement.

 

That is a pretty good analogy.

 

The measurement (which dates from 1981) in the article in Linear Audio was for a V15IV in the super light weight SMEIII arm. With the damper brush in the up position, there was a 15dB resonant peak at 8Hz. With the damper down, the resonant peak is 7dB (so 8dB lower) and the resonant peak moves to 11Hz. Adding the SME fluid damper reduces the peak to 4dB (a further 3dB) and moves that to 12Hz. That remaining 4dB peak is insignificant, certainly as compared with the original 15dB

 

that is not and never was the primary target for the Shure stabilizer brush - the target and principle goal was improved tracking - any coincidental benefits were just that

your analogy with a car shock absorber is accurate and applicable in one respect -
it most certainly can, and at times quite effectively, help an arm deal with warps and more (undulations/pot holes/rough pavement etc, to continue with your analogy) and to help alleviate "cartridge pumping" - which can induce acoustic feedback or howling
- that was the intent
- but it does not address the core problem directly and that is
- troublesome in room frequencies, especially at higher SPLs
- the Shure brush functions as a reactive device - it's an after the fact intervention or counterforce - it's effects are not continual or consistent (like the name says "dynamic")
- on a clean, FLAT record it may as well not be there - as is the case with a damping trough or cup
any help with sympathetic resonance energy emanating from the actual grooves, or your speakers, along with the subsequent Doppler effect, was and is, just a fortunate coincidence - the stylus is going to "see" what's in that groove with or without that brush (I recognize the brush's ability to shift points a dB or two - irrelevant) the impact on the tonearm's bearings will be negligible if at all

electronic subsonic filters are most frequently engaged to address playback problems experienced at high(er) SPLs coupled with poor room acoustics - lacking system set up or isolation - or when playing poorly made discs (there is some crossover efficacy regarding warped discs - the electronic filter still being the more effective of the two, with the exception of helping to reduce cartridge pumping in which case the brush wins (obviously)

that's pretty much where the similarities of the two devices ends

the Shure "stabilizer" brush was in response to lower tracking VTFs, higher compliance designs, STEREO records becoming more and more mainstream, arms getting lighter and lighter with every model year (but still, typically with so so bearings being used in mass market designs) the advent of lighter and not always so flat, "hotter" pressings and most importantly Rock n' Roll which in most instances wasn't making it's way to the best arms, tables, or rooms of the day (meaning more customer complaints about tracking issues) all hitting practically at the same time (well, decade anyhow) - in other words, "problems" with the records and the hardware playing them

when that brush came along around V-15 type IV time lots of people were really jacking up the volume in not so ideal situations

even with that said, to this day, I've read enough to know it is still the subject of many a harangue and much debate - there will always be a loyal proponent to whatever camp (the "up" or "down" teams)

I think this also applies to the implementation of fluid trough or cup damping, after the fact, for a multitude of scenarios - and that's fine - whatever let's you enjoy your records - it's all good - but in both instances they were still "add ons" (in Shure's defense the brush was considered with the totality of the design and using it always an option - same as a subsonic filter switch) it is also less intrusive
- how effective, if at all - on a case by case basis and never as effective or predictable as a well executed notch filter

on the other hand - fluid damping is "on" all the time you are playing a side, be it pristine flat, slightly warped or a salad bowl - affecting the arm/cartridge pairing at all times - even when it's not necessary -

fluid damping on an arm whose design incorporated it from the get go, and hopefully "voiced" with it (the unipivots) is one thing, but adding it on, after the fact, as a "mod" or an "performance upgrade" in an effort to cure an ill is in effect turning it into a different combination, throughout the entire frequency range
- I can only see it being predictable in it's behavior with a dedicated, specific, proprietary cartridge design (I am aware of the constant tuning and fiddling that can be part of it - but without a scope it's technically meaningless and to me it's unnecessary work)

it's back to my favorite drum to beat - the first thing to get right with your system is your ROOM, no matter what you got.............the next, set up (equipment and speaker placement)

there are better ways (tweaks if that's your thing) to overcome resonance issues than to stick the end of a tonearm in goop

yes, you see it on more than a few (well respected in their day, or so the magazines said) vintage (and a few new) unipivots due to the weebles wobble but they don't fall down nature of the unipivots' "no bearings bearing" (an issue recently addressed elegantly by VPI no less)

- I think it's worth noting too that VPI (some of the best sounding on the planet) is gradually moving away from their signature, and again, GREAT sounding, unipivots
- worth keeping in mind too is that a good gimbaled arm costs a lot more to build
- their new 3D unipivot arms call for no fluid and the older models that do, like the JMW 9? it's drop or two and only then as needed (cart dependent) - no boat rudder in a cup deal no matter what cart you may choose to run

spending a lot of money on gyroscope quality vertical and horizontal bearings to allow for almost friction free arm movement paired with a cartridge exhibiting near perfect channel matching and then turning around and sticking the arm in a highly viscous fluid in order to address an acoustic feedback issue after the fact?

or one engraved on the disc!?

- counter intuitive and counter productive - all you've accomplished is making the cartridge work harder under less than optimal working conditions while limiting speed for the sake of a room (or disc) issue - think how much better most carts sound after an hour of playing time or in a warm room

the greatest rub for me is that no cartridge's suspension (sticking with your shock absorber analogy) was designed to work fighting against this secondary suspension system (meaning you have now slowed everything down - on the vertical and the horizontal planes) - it's like overloading your F-150's cargo bed with too many pavers - something up front's going to suffer or at least change

you may cure the howl but you pay the price in greatly reduced transient speeds and inner detail

even the lowest compliance carts on the market (like DJ stuff) have their suspensions designed with as stiction free an operating environment as is possible for the intended application in mind - an "ideal"

just the effects of VTF's force on cantilever suspension, orientation and geometry has long proven a challenge to engineers
(that being, the centering of pole pieces/magnets at rest and their ability to recover, almost instantaneously (in a perfect world at the speed of sound) all the while having to cope with, and accurately trace, highly modulated passages of grooves) AND having to consider the wide range of arms and tables out in the wild - it is still the area of most cartridge improvements to this day

- the tighter the tolerances are on the cartridge, the more important friction free bearings and set up become

why add a new dimension which in effect is like coupling your cantilever to a diode and a capacitor to ground when there are better alternatives available? (and most of those are free or almost free)

damping troughs work - no argument here - but so does taping a wad of polyphil over an offending tweeter that's too bright or harsh - you may have solved the initial complaint but at what cost?

"in addition to" fixes seldom stop "working" precisely at some ideal line of demarcation (where you want them to work, or stop) but continue on into regions where their effects may not be desired - even if tuned to one set of variables, that goes out the window when another comes into play

there are less intrusive ways to damp arm tubes than the oil trough approach and at the same time retain the stiction free movement of those expensive bearings and cartridge suspension you paid good money for

like wrapping (coatings) or stuffing the arm tube (lot of/most good arms I see out today are taking that approach) Technics did it for years (High SPLs at the Disco anyone? - good name for an album) - just to suggest a couple

fluid damping of the type we are discussing here (the add on variety) is a vestige from a different time/philosophy when most tonearm bearings available to/used by/owned by most people (and in some cases, materials) didn't come close to what we have and understand today - that, or "fixing" a problem encountered in a hostile environment where the highest possible fidelity isn't always the number one concern (like a night club)

I have an old soft cover book of my father's that Audio Amateur put out 20 years ago - "The LP is Back!" - it is a collection of technical articles, do it yourself projects and tweaks
It's a fun book to peruse, but you will quickly realize that it's more a look back at past practices rather than anything really useful today - it is a collection of articles that are very dated (but still fun)
some of the stuff in it will put a smile on your face and almost qualify as "contraptions"

to me, in my opinion, for use on a well designed and executed modern tonearm (one built in my lifetime, or maybe the past 40 years that is NOT a unipivot) that is what add on aftermarket fluid damping is - it's a band aid at best

10 pound transcription arms need not apply! : - )

if you have low frequency resonance nodes/resonance problems in your listening space/set up - fix them - if you are trying to play that specific Lp that just wants to defy reason, push the "subsonic/rumble" filter button, and or, turn the volume down
if you don't have a filter? get one - they come in all different flavors so no need to argue about that - guilt free

electronic filters can be turned on and off in a second as needed - same goes for the Shure brush - not so much for fluid damping

don't jack up your nice tonearm/cartridge with some "mod/upgrade" mitigator solution from 1975 - it's all about bearing quality, set up, mass and the room -

gyroscopes still work on the bridge of a ship during a firefight, no damping required - anything else is a workaround, even on classic legacy designs

get a filter if you don't already have one and fix your set up (mass and good isolation are great friends to have)

Michael

 

What a long post! Anyhow that point is wrong. A navigational gyro on board ship has a very sophisticated oil damper. For example Submarine Electrical Systems - Chapter 17 and in particular the statement (there are several to the same effect)

"17E7. Oil damping system. On the east side of the sensitive element frame are 2 tanks partly filled with oil and connected at the bottom by a pipe. (See Figure 17-30.) Were it not for this damping system, the element would continually oscillate back and forth across the meridian instead of settling down into its correct position. The illustration shows the tanks in a sectional view. They are aligned parallel to the meridian and are totally enclosed. The tanks are connected by a pipeline at the bottom for oil, and by another at the top for air. They are filled to a depth of 1 1/4 in.

In order to obtain the proper damping percentage, it is necessary to restrict the flow of oil between the tanks. This is accomplished by means of an obstruction inserted in the pipeline.

To avoid the damping error, it is necessary to nullify the effect of the damping system during changes in course. To prevent the flow of oil due to the accelerating forces present during a turn, a damping cutout valve is placed in the oil line connecting the two damping tanks. This valve operates whenever the change in ship's course is greater than 15 degrees and it is controlled automatically by a pair of contacts in the transmitter assembly. The valve consists of a steel ball, inside the oil line, which can be drawn up vertically against a spherical seat by an external electromagnet when the oil flow is stopped. Thus, the valve is operated without disturbing the equilibrium of the sensitive element."

 

It´s hard to get a summary of what You write, it´s really mixed. My take is You think arms with damping works in a way they don´t.

 

Is it the "after-market" nature of some of these fluid damping solutions that have you so worked up? There aren't too many after-market such solutions. KAB makes one for those Technics arms, and SME made one for its own arms. More often it's incorporated in the design itself -- like it is in some of the best tonearms made today, like the Graham Phantom, the JMW unipivot, the SME 312S. Either way, integral or aftermarket, it works the same, provided it's well designed for the application with regard to mass, fluid viscosity, size and shape of any paddles, etc.

Of course something like the KAB subsonic filter is also an after-market add on, and an ex post factor workaround for a mechanical issue -- subsonic mass-compliance spring resonance (it is a mechanical challenge that has zero to do with the room, in an anechoic chamber, you'd still have it, with the volume of the turntable turned to zero, its still happening -- the record spinning itself, because it's not perfectly flat, not perfectly centered, and because the vinyl surface, independent of the intentional groove wall modulations, is not polished smooth, is setting the spring in motion) which hasn't been addressed mechanically by the tonearm or turntable manufacturer. Fluid damping will help with structure borne vibration problems, and probably more so than a lot turntable structure isolation solution many of which are not very effective at very low frequencies, but solutions for structure borne vibrations will not address motion touched off by the spinning record itself, or by motor breakthrough for that matter, though that tends to be at a higher frequency.

Wrapping coatings or stiffening the arm tube work on arm tube ringing, they don't work on mass-compliance spring ringing, these two things address two completely different mechanical issues. Wrapping a tonearm won't have any effect on the mass-spring resonance except very, very slightly changing its frequency by adding more mass to the system. It won't stop the mass-compliance resonance from existing, and it won't damp its motion (and it's closer to your analogy of overloading a pickup truck. Fluid damping of low frequency arm movement in the horizontal and lateral planes doesn't load down the cartridge suspension, though adding tonearm mass might).

I'm not a mechanical engineer, but I'm not sure it's true that you've slowed everything down when you apply viscous damping. It depends on the velocity of the motion and the viscosity of the fluid, just like you can swing your arm more slowly through water more easily than you can do it fast through water. Also, the motion of the arm doesn't really effect the speed of the cartridge as it react to transients. The whole idea is to hold the arm as close to motionless as possible and let the cart/stylus/cantilever/suspension move. Damping the tonearm's low frequency left right and up down motion, doesn't damp the stylus/cantelever's HF up down, left right motion.

I don't know about nautical gyroscopes, but I'll that @Just Walking's reference to be accurate, that they have viscous damping incorporated in their designs. Viscous fluid damping is all over the place in our lives to deal reactively with shock -- like in our car's shock absorbers. Like I've said before, we're not talking about weird science here. We're talking about a mechanical system -- turntable, tonearm, cartridge -- and dealing with inherent mechanical resonances in the system resulting from trying to play a spinning record.

Like fluid damping, hate fluid damping, use fluid damping, don't use fluid damping, I don't care. It makes no difference to me what you or anyone else uses. Play CDs, play records, play MP3s, stream, whatever. But most turntables and tonearms are built to a price point and are under designed and under built with respect to the audible effects of mechanical resonances in the playback system itself.

 

But don't they often ring at audible frequencies too- e.g. 100- 150 Hz or so? I've seen test reports that show this to be the peak resonant frequency for different arms- greater than the peak found at the mass vs. compliance relationship which is usually around 10Hz.

 

Yes there are structural resonances in the tone arm itself, and indeed in any structure. That is why halfway decent arms are internally damped. The old SME trick was to insert a tight fitting square section stick of balsa wood down the arm - very little additional mass but good frictional damping if tight to the internal arm diameter. Later on in the IV and V arms, they are tapered section and made from titanium alloy (by Chicago White Metals Precision Die Casting Supplier - Chicago White Metal Casting the only part that is not made in their factory in the UK). It also has an internal layer of damping goop of secret composition to damp any remaining resonances. That tapered part is also used in the 300 and 312S arms. The fact that it is tapered breaks up resonances and reduces effective mass.

While I'm extolling the virtues of SME, the counterbalance weight is mainly tungsten. Reason is that tungsten is very dense (twice the density of lead), so it dramatically reduces effective mass by putting the counterbalance really close to the pivot. And the damper is a rod (rather than a paddle) with calibration marks on it so you can adjust the damping - or even pull the damper out of the bath and lock it in place. So you have the flexibility of how much damping from maximum to none at all, and anything in between.

But there are many ways to square the circle of arm design, and there are many excellent arms out there. And like any mechanical design, every arm is an art in choosing what compromises to make. And designs which are "no compromise" are stupidly expensive. Like the now defunct Rockport Sirius, which used a parallel tracking arm, and for the deck and arm was around $75k. Of course parallel tracking is nothing new (B&O had that in the early 70's), but it has the massive benefit of being short - only enough to do the job so 6" long - and so is stiff (stiffness goes as 1/length squared), and there is no tracking error. And if you get the air bearing design right, you get damping into the bargain.

 

maybe my example was too complex (and a different machine altogether)
the damping described (and the excerpt you cite) has nothing to do with the gyro wheel proper - our case the tonearm gimbal
most folks don't use there turntables on a rolling sea, but if they did, the system(s) (gyrocompass) described in that article would be for the turntable and it's stand or rack in combination, not just the tonearm itself (to keep things simple and clear)
you wouldn't suspend your table from the ceiling and then push it like a swing, to and fro, and expect it to stay level (or track properly)
not being silly - that is what is being discussed - preventing/controlling the whole from behaving like a pendulum
read the entire article
Michael

 

Hi-Fi News has quite a few tonearms now tested with Paul Miller's suite of tools and always shows the cumulative resonant decay waterfall plots. Sometimes difficult to draw any conclusions, especially devoid of his commentary, as in the few popular table/arms I grabbed and posted below, but interesting nonetheless. Main thing to look for is quick decay and narrow bandwidth in the resonances, obviously they can't be avoided to some extent ...

MoFi UltraDeck




Technics SL-1200GR




Rega RB2000 tonearm




Acoustic Signature TA-1000 Tonearm




SME V tonearm

 

Excellent post Davey, thank you. Since these responses are smack in the audible ranges, (without any measurement basis to back it up) I believe this is where different mats and possibly headshells can make a difference in taming (or increasing) some of these resonances. It would be really interesting to do the same analysis with different combinations of mats and headshells.
To my ears the dense closed cell foam mats work best if a clean, uncolored sound is your goal.

 

you need a "summary"?
fluid damping (trough or cup) = steady state solution affects entire tonearm cartridge system design parameters via friction and physical coupling resulting in loss of transient speed and inhibiting cartridge suspension recovery time in order to "solve" a problem easily addressed by less, or non intrusive means = not desirable

Shure "Dynamic Stabilizer" = reactive solution (primarily for another set of transient problems) i.e. warp(s) and faulty lead-ins among others - when no transient problem is present the device behaves in an entirely passive role (contact with the record surface is occurring during "normal" play but is off set with proper VTF settings) = desirable

Apples to oranges

Michael