Tonearm microphonics
rauliruegas Do you mean that you tested before bougth it in your today cartridge room/system?Yes. I almost always evaluate components first-hand before making a purchase. |
@bdp24 Can an arm be "too" damped, too non-resonant? Are those two things the same?Not really. Removing resonance from the arm tube is a good thing and its impossible to overdamp the arm tube in this regard. One **massive** problem with that though: messing with the mechanical resonance caused by the compliance of the cantilever and the cartridge/arm mass is not good, unless by doing so you get it inside the 7-12Hz window. So if you are applying damping materials to the arm, you can mess that up and with dreadful results. Damping can be done by a damping trough too; which is an entirely different form of damping, but IME that can lead to problems especially if the LP is not perfectly flat. Generally speaking the arm will not need this kind of damping if the mechanical resonance is in the right window. So you have to be careful when bandying these terms about. They can mean three or four different things depending on who you're talking to and that's on a good day! |
bdp24, Yes, I do think it is possible to overdo damping. Specifically with tonearms, I have experimented with the damping fluid level in my Basis Vector arm and heard the difference with the fluid level in the damping trough of an SME arm. Too much damping results in a lifeless sound. I think tuning of resonance and damping of vibrations in all parts of the reproduction chain is NOT a matter of trying to minimize vibration to the utmost. I was in attendance when a representative from Symposium tried different shelves under a CD player. The very top model that Symposium offered, that does the most to dissipate vibrations as heat, actually sounded quite bad--dry and thin. The representative agreed with this assessment; there can be too much damping. I've heard the same with devices for placing under speakers, exotic racks, etc. I spoke with someone in the high end industry that has heard hundreds of different systems. He said that he has NEVER liked the sound of a system employing exotic and extremely expensive vibration damping rack/shelves. |
Atmasphere is right to point out that there are adverse side effects where the geometry of the disc is not uniform and flat when external damping in the form of silicon goop is applied. Not only does it damp resonance but it also exerts drag on the arm's movements not unlike extra friction in the bearing. this means if the arm has to weave from side to side or follow vertical undulations there will be slower reaction. However, here's the kicker : even if the disc was drilled perfectly centrally and was perfectly flat there would still be a problem because the tone arm must "sign" across the disc as it still must follow the inward "spiral" of the groove to its centre. Therefore Stringreen's suggestion was extremely sensible i.e. if the arm seems naturally well enough damped, try to run it without damping fluid. |
In his original review of the Well Tempered arm, and in Bill Firebaugh’s literature on his arm, Gordon Holt discussed the viscosity of the arm’s "bearing" well damping fluid, and how it allows the arm to freely move at very low frequencies (those of the arm following the groove, warps, etc.), but keeps the arm’s bearing rigid above those frequencies, such that it allows it to act as a normal mechanical bearing, but with very low friction, and no bearing rattling or chatter The Townshend Rock turntables damping trough behaves in the same manner; warps are "slow" enough to not impede the movement of the arm in response to them (up and down), and the same with groove eccentricity (left and right). Those frequencies are very low, far below the lowest contained in recordings. At audio frequencies, the viscosity of the damping fluid in the trough is heavy enough to "lock" the front of the arm in place, just as an arm’s bearings do at the arm’s rear. The result is the tightest, cleanest bass I’ve ever heard from LP’s. LP surface noise is diminished as well, and violins take on a smooth sheen, their timbre sounding organic, not electronic, bright, or etched. The resonance-reducing capability of the Rock system also increases the audibility of inner detail (listen to one of the great recordings of the large choral groups Robert Fulton made---every voice is individually audible, or the massed string section of a symphony orchestra) , and micro-dynamics. With the low-level "haze" (that created by uncontrolled resonances in the playback machine) removed from the sound of LP’s, the sound IS more like that from master tapes, the mechanical nature of LP reproduction reduced. Does this sound like a commercial ;-) ? One interesting thing discovered with The Rock is that it decreases the difference in the sound of arms mounted on it, the damping apparently compensating for the less well-damped nature of cheaper arms. |
To clarify, the relationship between warp and eccentricity demands on the ability of the arm to follow them, and the frequencies involved in those demands, are a matter of the time it takes the arm's headshell to traverse a warp or eccentricity. If a warp takes the arm's headshell a full second to travel up and then back down, the frequency involved is 1Hz. The same for an eccentricity that it takes the headshell a second to follow left and then right, back to where it started; one second equals 1Hz. If the warp or eccentricity take 0.5 seconds to traverse, the frequency is 2Hz, and so on. |
Regards. Correct me if I'm wrong, I really don't mind. A cartridge doesn't care where it's signal comes from and if any constituent part of a turntable can resonate, it will. Resonance can be either constructive or destructive, airborne or mechanical. Constructive resonances are typically considered to primarily fall in either the fifth harmonic or at the first octave, The enhancement of these resonances are usually considered pleasant, sometimes even desirable (think piano or strings). Destructive resonances may be generated by extraneous mechanical vibration or reflected airborne energy such as sound reflected from walls, a nearby speaker or other objects close by. This may also be described as proximity resonance. Sources of these resonances can be autonomous, sometimes described in terms of Eigen value. Imagine a large, heavy plinth coupled to a light tonearm. If the plinth is energized it will act on the tonearm to some commensurate degree. The tonearm resonates to it's own value. When these resonances couple to resonate in phase and not disproportionate to the recorded signal these resonances may be said by some listeners to be considered as desirable. Resonances not in phase are said to be destructive. In this sense and depending on degree, damping can generate either constructive or destructive resonances. Just when one thinks they've a handle on the phenomena and your turntable is performing in a wonderfully synergistic manner, a change of cartridge or headshell shifts mass, nodes are redistributed, phase goes out of kilter and unanticipated boundary resonances return unwanted signals. The cartridge doesn't care where the signal comes from. Peace, |
Dear Bdp24, Sincere thanks for your excellent and well written post. I knew that if we “mechanical laymen” poked the problem with a stick for long enough, someone would weigh in with some actual research ;) I had completely forgotten about the Rock. It is one of the most well-researched turntables in analogue history. If Townsend says that damping works regardless of adverse conditions then that’s good enough for me. :) Best regards, Bill. |
If I understand how viscous damping works, resistance increases with velocity of movement. As an example, if you put your hand in water and move it very slowly, there is very little resistance to movement. But, try to move it fast, and the resistance increases dramatically. When a tone arm has to make large lateral movements (e.g., off center record) , it is forced to move at a much higher velocity than its normal movement, which is quite slow. I don't know if this added resistance is enough to create excessive strain on the cantilever or the suspension, but, I would guess that fluid damping is not a help in these situations. But, some resistance to movement laterally might be a help when it comes to bass response. Deep bass is often cut monophonically so that all of the movement is laterally. If the movement is large enough, the whole arm will move instead of the arm being held steady (stead would mean all of the movement of the cantilever is translated into signal). Thus, movement of the arm to follow the groove results in reduced bass response. If damping helps to resist such movement, bass response would be more powerful and faithful to the signal on the record. The Moerch DP9 anisotropic arm does this by increasing the effective mass of the arm in the lateral plane of movement; I bet damping would provide similar resistance as well. |
Dear @larryi : You are rigth about that " resistance " that more than affect the cantilever could " affect " suspension but I think maybe not something to worry about and when this " trade-off ( that we don't know for sure it's a real trade-off. ) goes infavor of that better bass response then we have to go a head with. Remember that the foundation of music belongs to that frequency range. In the other side the huge forces generated at stylus tip/grooves are of different kind and till we can measure we just can't know if that resistance is really " dangerous ". Could be that's compensated " some way ", maybe not but that kind of damping is welcomed because its virtues in favor of MUSIC. Regards and enjoy the MUSIC NOT DISTORTIONS, R. |
Dear @atmasphere and friends: Damping is always welcomed and especially against undamped tonearm designs. Now, resonat frequency can't change with damping. The only way that that frequency can change is if we modify effective mass and/or cartridge compliance. Of course that if we have that silicon damping type that mantain cartridge compliance out of work then it's another matters but this is almost imposible to happen. @larryi said that in the Vector ( unipivot design. ) / SME tonearms to much damping and sound becomes lifeless/dull. Now, he posted an additional example about with the Symposium items but both examples in true can't tell us that are overdampening in here but the other way around and let me explain it: I'm totally convinced that we can't overdamp any audio item ( of course that unipivots that use silicon at the pivot can be overdamped when that damping impede the bearing function/movements. ) under normal circumstances. We are accustomed to those " beningn/good " resonances @timeltel ( btw, welcome back. ) spoke but exist no real " good/welcomed " resonances. Any vibrations/resonances in more or less way always degrade the audio signal information that was recorded in those LP grooves. We want that what the cartridge pick-up down there be only music information something impossible to achieve. So next down " step " is to mantain those " resonances " at minimum and this includes the " good " ones. I don't want to tolerate any audio signal degradation for whatever reasons that degradation comes and that's why damping is always welcomed. The Rock example is very good one as is too the WT one. Sometime ago in other thread a gentleman posted that he did not like it the after market AT hold-down LP ( pump. ) because it puts the sound with the same atributes larry told us: lifeless and dull. For he these were a bad thing when in reality is a good thing because is reducing resonances/vibrations/degradation/distortions. Overall problem with all those 3 damping examples is that we are accustomed to very high " resonances " that we like it because too many time living with but this fact does not means is rigth because is wrong. That's why I always say that the important issue is not what we like it but how should be what we need to listen. Regards and enjoy the MUSIC NOT DISTORTIONS, R. |
I'm glad this subject was broached. I've been in contact, just this week, with two well known experts in the hi-fi field, concerning acoustical feedback in my TT, when playing low frequency LP's at a louder than normal level. The bass begins to build on itself and in a few seconds, I have a low frequency feedback problem. In reading this thread, I noticed it was mentioned, one should never get any sound, when tapping on the TT plinth. I have a VPI Scoutmaster, with a JMW-9 signature tonearm. The cart is a Dynavector DRT XV-1s. With the tonearm at the end of the record, I can tap on the plinth with my finger and clearly hear the thumping noise through my speakers. I have tried a couple of methods to dampen the tonearm (haven't tried the shell yet-there really isn't one) to no avail. I'm thinking this has to be contributing to my problem. I have also tried dampening the plinth by placing sealed bags of sand on top of it any trying the same test. The tapping noise is still there and has not been diminished in any way. I wanted to employ a subsonic filter that would eliminate all frequencies below 10-15 hz on my subwoofers, as when they're turned off, the problem goes away, but can't find one. I'd rather not go the KAB way as I think I would be losing some of my good frequency response. I realize most of my problem, must be coming from my tonearm, but was curious about the plinth comment. Does anyone have words of wisdom for me about my tonearm and plinth? BTW, I've tried rearranging my subs and have significant room treatment. My room is not just an untreated shell. |
@handymann A year ago or so, I had the same problem as you, especially with LOMC cartridges. The solution was isolating the turntable. In my case, I used Anvil turntables excellent magnetic footers, but I'm sure there are other good solutions. These isolating footers works despite the fact that my table was in the front corner next to the speaker with a powered sub. Ultimately, further improvements to the sound of my system occurred when I moved the turntable out of the front corner to the rear of the room using a long XLR connection between amp and preamp. FWIW, I tried the tap test on my Koetsu/FR-64S combo this am, with the pre at playback volume. I heard nothing through the speakers. Admittedly, I didn't have someone's ear right in front of the speaker. |
BTW, I have one TT on an inner tube and spiked, the VPI is spiked (it comes with it's own adjustable spiked feet) onto the discs that come with spikes. The spike discs are on rubber compressor feet and my TT platform is isolated from the wall. I don't think it's an isolation problem. I can tap on my platform, when the record is tracking out and I hear nothing through my speakers-standing at my TT position. Thanks for the input-always wanting to learn. |
Dear @handymann : Do you own other LOMC cartridge you can test on that TT/tonearm?. I'm not talking that you make tests with other cartridge tapping the TT but just listen at those SPL with LP recordings that has high low bass. Btw, which cartridge did you use it before the XV-1s where I could think you did not aware of the problem or you had it? I think that first than all is to be aware if those high low bass room SPL affects the racks you are using in the system. Remember that at room corners low bass SPL is " concentrated " and with subwoofers that goes as low 10hz or even lower with high SPL at the volume its distortion levels goes higher than normal . In other side maybe the subs are reproducing low bass oscilations that comes elsewhere from the system but I can't be sure on this. The plinth tapping is non adequated test for your problem rigth now. First you have to identify where is generated the problem and depending this will be the solution or solutions. Even maybe some friend (s ) can borrow you other cartridges to make those tests. Repeat not tapping. You can check too that at those SPL/volume gain running the VPI TT but with the tonearm/cartridge at rest: take a look to the subwoofer drivers if exist any movement there or at the speakers woofers. After those tests you and us can have a better " stage " of what's happening before to follow at " blind " way. Regards and enjoy the MUSIC NOT DISTORTIONS, R. |
Hi Raul: I've seen your name mentioned in several discussions, but don't know anything about you and really don't need to. From other's comments, people look to you for advice. I'm 63 years young and have been into sound since I was four. I was given a "real" record player for Christmas and after seeing my uncle string speakers across my grandparents room, went home and disassembled my record player, to see if I could do the same. My dad bought me a 4" speaker to play with and I've been hooked ever since. I'm going to address some of your questions, but I need to give you info about my equipment and room. It's 19' x 21' x 10' high. I have a dropped acoustic tile ceiling that's about twelve inches lower, with 8" fiberglass batts resting on that. I have about 12 acoustic panels made of 1" hard fiberglass, covered with speaker cloth, that are on the 45 degree walls leading up to the ceiling (jump ahead to get a description of the walls) and are 2" out from the wall itself. I have 4 home made ASC-like tube traps strategically placed. I think my room is too small, for the energy I'm trying to introduce in it. I'm using 2 Fathom 113 subs that are diagonally placed, almost facing each other, about 4-5' out from each corner, with one being set 180 degrees out of phase, to help with cancellation. My room has knee walls aprox five feet tall, then goes into a 45 degree angle to the ceiling. The ceiling is about 8' wide. I read Jim Smith's book and decided to place my TT on the left wall, between my listening area and the speakers. The speakers are about 8.5' apart, 3 and 4' from the side and rear walls and 9.5 feet from the listening area. Because my floor is on the second story and is on a suspended floor, I eventually had to separate the TT platform from the wall and using heavy duty springs, eye bolts, steel cables and turnbuckles, successfully achieved a kind of floating shelf. No more problems with walking across the floor etc. To your question about different carts. I have a 1974 Pioneer PL 71 that has a Koetsu Urishi Black on it and I can run it a good 3-6 Db higher, before I get any feedback-maybe even higher than that. I have a Sony ESD 2000 preamp I run my subs through, for convenient remote control and separate gain control. This way, I can vary the volume of the sub, depending on what record I'm listening to. Today I added some dampening fluid to the VPI, but it didn't seem to help. I once had a Lyra Delos on the VPI, but have added another sub since then. I'm thinking I had the same problem then. I'm not saying I can't listen at a comfortable level, but if I turn it up, (85-90 db) I get an acoustical feedback problem. I was told by some of the best, that's just the way it is. I would appreciate any solace you can provide. BTW-no woofer movement, when not playing. Wish I could find a subsonic filter, single or double channel that would filter out 15hz and down. |
Dear @handymann : I assume that the ARO told you that those subwoofers positions gives you " flat " bass response, rigth? Now, in any stereo audio system with passive main speakers and powered subwoofers those main speakers must be running as " satellite " ones, this means running from around 80 hz and up and the subwoofers covering from 80 hz and down. But even that you could have " flat " response at your seat position you need to test the response at TT position that’s where the problem is happening. You said that you already " play " with different locations for the subs and this subs position is critical when we want that the subs be perfectly integrated to the stereo audio system. In my case and after more than a year " playing " with the best location in my room/system is both subwoofers rigth in front of the speakers facing each to other ( not facing at seat position. ), are in a " free " space. Now, the first and main target when we integrated a pair of powered subs in a " passive " system is that IMD/THD goes really down, first at the main speakers and as consequence of that to the whole audio system. Second target is to improve the quality level reproduction of the bass range ( that’s the foundation of the MUSIC, it’s where MUSIC belongs. Not at the mid-range. ). Third target is to add a half or one and half bass octave to the audio system. Main target when subs are integrated in the system is: that we can’t " hear " those subwoofers, that we be aware of only when the recording ask for, this means that the SPL/volume subs set up must be just PERFECT and stay that way always and not be change it by us depending on the recordings we are listening: NO. In the other side. the THD of your subwoofers is really high when its specs says around 10% at 50hz at 120db, this figure is not a good one. My Velodyne’s has 0.5% not at 50 hz but at 20 hz ! ! ! . Big and critical differences. Try to make those tests at TT position and that main speakers only handle the frequency range from 80 hz and up, play again with subs position and critical that SPL/volume on those subs that must be fixed. Regrads and enjoy the MUSIC NOT DISTORTIONS, R. Btw, 85 db at seat position is something that when subs are well integrated in the system produce no single problem. I measured SPL at my seat position over 95 dbs with out be awared of problems down there. My TTs are in between the speakers. |
Hi Raul: I have a couple of Wilson Maxx II's. They're rated @ 20hz, but they don't quite get there. If I place my subs in front of the speakers, won't that block my main bass? I have had the subs facing each other before, but they were behind my speakers. That placed them too close to the corner and overemphasized the bass. I saw a picture of a guys room and he had his on each side of his listening chair pointed away from him. I need to build a couple of diaphragmatic absorbers, as well as a couple QRD-13 dispersion panels. Won't help my current problem, but may help the over all sound. Do you incorporate these devices? I have my sub sourced through my tape out on my Calypso preamp and have the subs rolled off around 35hz, so most of the main bass will go through my main speakers. I kinda like to play with the sub volume, specially on old LP's where they rolled off the bass to high. I know it's not "real", but still sounds better to me, than the rolled off sound. When playing quality LP's and the occasional CD, I set the sub volume and leave it. I was listening to The Thompson Twins "Through The Gap" the other day with my mains turned down low. I heard some really good low frequency, I hadn't realized was just coming through the subs, so I think I get them matched up pretty well. It's fun to just listen to the subs sometimes, just to hear things like that. Sounds like your subs are really good. Wish I had shopped around more, but mine are OK. I'm still open to suggestions. As I said, wish I could find a filter to block everything from around 15hz and down. |
Correct me if I'm wrong, I really don't mind. A cartridge doesn't care where it's signal comes from and if any constituent part of a turntable can resonate, it will. Resonance can be either constructive or destructive@timeltel, I respectfully ask you to look up the definition of resonance as it relates to vibrations. It is a condition that increases the amplitude of vibration greatly and as such cannot be constructive. What's worse is you are using a mechanism where a vibrating stylus is used to reproduce the recorded sound. If you care at all about accuracy in sound, you do not want a resonance in the audio band. |
Regards, rotarius: Thanks for the considerate manner of your post. Please consider: "Constructive" and "Desirable" are not necessarily synonyms. First, neither are resonance or interference technically the same. However, when considering transducers sometimes resonance can generate interference. Here're a couple of relatively easy to grasp descriptions from: Frank Heile, P.h.D. Physics, Stanford University (quote): "Resonance is when a driving force is at a frequency that is close to the natural oscillation frequency of a system. This makes the amplitude of the oscillation of the system greatly increase. Interference is when two waves at similar frequencies are superimposed which results in either constructive interference when the waves are in phase and add together, or destructive interference when the waves are out of phase and interfere with each other." And: Bruce Thompson, former Computer programmer at University of California, Berkeley: "In some systems it makes sense to use either "interference" or "resonance" to describe what is happening. For example in a trumpet, the waves created by the vibration of the player's lips interfere constructively, creating a resonance effect." In a paper presented to the AES, Shure technician C. A. Anderson states: "Resonance exists because the arm and pickup assembly behaves like an effective mass that is coupled to the record groove by means of a stylus assembly with its own mass, compliance, and mechanical resistance". If a 1kHz signal recorded to vinyl represents a displacement of 80 microns (according to a study by St. Andrews College), it would be difficult to argue that unwanted vibrations of the tonearm have no influence on the signal. The cantilever doesn't discriminate from which end movement originates, sometimes the tail DOES wag the dog. ;-) When a recorded signal matches the natural resonance of our tonearm/cartridge, Mr. Anderson states the recorded signal can be enhanced by 6 to 20 dBl. He doesn't state such but with out of phase resonances then distortion, diminution or even cancellation of signal at specific frequencies might be anticipated. Resonances can then be considered as constructive or destructive. Poem. by Henry Gibson Her name was Grace, she was one of the best, Late last night I put her to the test. She looked so sweet, pretty and slim. The night was quiet and the lights were dim. I set everything up as nicely as I could. I handled her gently for I knew she was good. She was just one big thrill and the best in the land. Then she hummed but it was not for joy. More effective damping was obviously in demand. Peace, |
Infection what I have done is used some of the plumbers teflon tape and wrapped the arm tube. It improved the sound so I left it. I would try that. If it sounds worse remove it or some of it. And Raul is right. It is like a microphone and I wouldn't lose too much sleep, tapping on the arm tube while at rest is no indication of how the arm will sound. In fact generally I have found that the better cartridges are worse for this as they are more sensitive. I have a VDH Colibri that will pick up a fly walking on the arm tube at rest. It sounds fantastic. Higher compliance carts are worse than low for this but that is the same feature that makes them so detailed and sound so great. |
Dear @handymann : You are using those subwoofers as bass re-inforcement, your call but is not the way to use it and I can tell you that the gentlemans that gave you that kind of advise were and are totally wrong. You need high-pass filter for you can use those subwoofers along the Wilson speakers in the correct way. Till you make that kind of set up you can't know what you could need. My advise is to do it and stop to think on that room treatment of 15 hz filter that only makes a signal degradations. The " ball " is in your field. regards and enjoy the MUSIC NOT DISTORTIONS, R. |
Raul: True story about me supplementing my bass. The Wilsons put out such good clean sound, I hate to roll them off, besides, I'd have to get an active crossover to roll the lows off @ 80hz. Maybe I will try it. If I installed a filter, that only cut 15hz and below, that wouldn't degrade my sound. I realize we feel some bass we can't hear, but 16hz is low enough for me. I have a Bag End sub that they say goes down to 8hz and the walls shake, as well as other things, before you ever "hear" any sound. I had it in a Home Theater system, but it's just sitting in the spare bedroom right now. I will continue to experiment with sub placement and frequency adjustments. Thanks for taking the time to respond. If you have any other suggestions, don't hesitate to tell me. |
BTW Handymann, I agree those MAXX2s of yours are glorious loudspeakers when working solo. I wouldn't be unhappy with them at all. Just leave the termites to their devices. (Pest controllers say that you can hear termites munching inside the walls. Do they mean one termite or a concerted symphonic throng? Apparently soldier termites can also be heard banging their heads off the walls. Now those guys MUST be Black Sabbath fans... ;) :) Best regards! |
