Thekong.
Thanks for posting the photo of the counterweight arm. One suggestion is that you need to be very carefull with the stiffness of this. Any shake rattle and roll here is bad since it is no longer free to pivot about the leaf spring. I experimneted with the rod carrying the weight and finished up with an aluminium rod with a M10 thread for adjustment. Smaller diameters were quite flexable. |
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Could the tubing being in a loop at the centre of the Rockport and Kuzma arm, be acting as a type of dampener for the arms motion in both directions ? Hi Ct, I think the tubing is just a necessary evil in the Rockport / Kuzma design. As for whether it affects the tracking, when I adjusted the arm to free floating (i.e. 0 VTF), I can put the arm in any position without it going in or out. So, I suppose the affect is minimal. However, there is one interesting point that I still can’t understand. When moving the arm in and out by hand, the feeling of the ET is smoother (or I should say requires less force) than the Rockport! While I don't have the spec. of the 2 bearings, I have always assumed that the Rockport has a tighter tolerance / air gap. This can be shown when trying to move the arms without the air supply. While you can still move the ET quite easily, a lot more force is required for the Rockport in this condition. But, when air pressure is supplied, shouldn't both of them be virtually frictionless? I think if the Rockport indeed has friction, the cartridge would probably mistrack. Or could it be the horizontal mass that we have been talking about? Based only on the look, if the horizontal mass of the Airline is 100g, I would estimate the Rockport is about half to 1/3 of that, so in the 35-50g range, not that far away from that of the ET! |
Hi Thekong Yes please post a pic of your ET2.5 with the modified counterweight when you can; would love to see it and look forward to your ET 2.5 impressions as well. I have had my ET2 on the left side of a table. I found it very awkward both from a handling and viewing (the cantilever) perspective. Then again I don’t get driving on the left side of the road either..... I am curious about the Rockport and Kuzma based on what Ketchup and yourself said regarding the tubing. Ketchup
What about that stiff plastic tubing on the Kuzma? It seems like it would have a huge effect on the arm's movement even if both of the fittings swiveled. Thekong
I can’t say they have no effect on movement, but they certainly don’t hinder it, at least not to the point of causing mistracking. Based on my ET2 experiences, the arm can be lined up properly and if the pump is decent it will track fine. But nowhere near its potential if the wiring is affecting its travel. So would not the best air bearing design/solution mean no wire(if it was possible) and tubing attached to the moving pieces, giving the cartridge/armtube the greatest freedom ? I'm just sayin' as a user. The Rockport and Kuzma tubing makes me think of my past experiences with my VPI JMW 12 tonearm. That tonearm’s wires are used as its antiskating method. Their positioning pushes the tonearm back toward the outside. Could the tubing being in a loop at the centre of the Rockport and Kuzma arm, be acting as a type of dampener for the arms motion in both directions ? Cheers |
Thekong,
Yes I agree with you. I only used the 12mm as that was what was used on the Kuzma video Richardkrebs referred to.
The key point as you have indicated is that the Kuzma and Terminator arms will have 3-400% higher lateral force on the cantilever due to their horizontal effective mass being 3-400% higher.
In my view this isn't great and I would worry about using medium to high compliance cartridges with these arms. From your comments I can see you are very careful on setting up your arms.
Will be very interesting to see what you think of the ET2.5 when you have had a chance to set it up. I would encourage you to try my set up recommendations, using my decoupled counterweight suggestion - which means running the I beam very very loose, and tuning the bottom end response by slowly adding dampening to the movement.
Bruce Thigpen has clearly put a lot of thought and experimentation into the decoupling methodology and the low mass.
If you read his manual and patents he starts with a low mass arm, and then brings the effective horizontal mass up very very gently by providing variable spring rates. This is to keep the resonances between horizontal, vertical in sync with the compliance of the cartidge and the Q of the system. The Q is related to the dampening of the oscillation - the use of magnetic dampening will shift this slightly. Very small adjustments can give quite dramatic changes to the sound, especially in speed and articulation. |
Dover
The fact that it takes considerably more force to accelerate a heavy arm sideways is self evident.
What I have constantly said is that this force will not be enough to deflect the cantilever while tracing an eccentric record, provided the resonant frequency of the arm / cartridge system is above 0.55 hz for a 33 rpm and 0.75 hz for a 45 rpm record.
The analogy I used earlier is a good practical test to show this phenomena. For those interested it would take 5 minutes of your time.
All you need is a rubber band representing the cartridge suspension ( spring) A weight, representing the arms effective mass, attached to the rubber band such that it bounces up and down at a few HZ, representing the resonant frequency of the combination. Remember the resonant frequency is a function of the arms effective mass and the cartridges suspension stiffness ( springiness)
The groove modulation is simulated by rapidly moving the rubber band up and down. ( The cantilever driving the suspension) Do this at frequencies higher than the bounce frequency and you will see that the weight stays still. In other words the cantilever is moving and the arm is not.
Now move the rubber band up and down at a frequency lower than the bounce frequency. This simulates an eccentric record or the lead in, lead out grooves. Now the weight moves up and down in total sync with the rubber band. The whole arm is moving and the rubber band is not stretching or retracting. The cantilever is not deflecting. |
What about that stiff plastic tubing on the Kuzma? It seems like it would have a huge effect on the arm's movement even if both of the fittings swiveled. Does anyone know any details about the tube's fittings or if it hinders the arm's movement? Hi Ketchup, My Rockport and my friend’s Airline shares similar arrangement in the airhost. Actually, they are not that stiff, and they can be detached at the point where they enter the bearing. So, you can twist them a bit to attain a hanging n shape for minimizing the effect on movement. I can’t say they have no effect on movement, but they certainly don’t hinder it, at least not to the point of causing mistracking. If the record is 12mm out of true, the arm travels 24mm in and out with each revolution, which takes 1.8 seconds. Hi Dover, While it may not affect you conclusion on the lateral forces of the 3 arms, a record that is 12mm out of true (24mm in and out, that is nearly 1 inch!) is probably unplayable even with a pivotal arm. I think, on average, 1mm (2mm in and out) is more like it! |
Comparison of lateral forces on Kuzma/Terminator/ET2/ET2krebs For those who are interested in understanding the side forces on the cantilever : Force = mass x Acceleration, where acceleration = mass/(velocity squared) If the record is 12mm out of true, the arm travels 24mm in and out with each revolution, which takes 1.8 seconds. On an eccentric record the acceleration will be the same for each arm – 0.0024metres / (1.8 sec x 1.8sec) = 0.00074 metres per second squared The horizontal effective masses of the 3 arms mentioned in this thread are: Kuzma has been quoted as 100g Terminator 80g ET2 25g The force on the cantilever is as follows: Kuzma = 0.1kg x 0.00074m/s2 = 0.000074 Newtons Terminator = 0.08kg x 0.00074 m/s2 = 0.000059 Newtons ET2 = 0.025kg x 0.00074 m/s2 = 0.000018 Newtons Summarising then you can see that the increased mass of the Terminator and Kuzma arms increase the lateral forces on the cantilever by 300-400% over the ET2. Now Krebs has modified his ET2 by adding 30gm of lead to the spindle. This adds 30g to the effective mass of the ET2. Krebs also couples the counterweight ( no spring ) which adds another 30g to the horizontal effective mass. So Krebs has increased the horizontal mass of the original ET2 from 0.025kg to 0.085kg. The Krebs modifications have increased the lateral forces on the cantilever by over 300%. Furthermore he employs no dampening to control this mass and runs his ET2 at a lower pressure of only 12psi. The arm moves in and out every 1.8 seconds. This equates to a frequency of 100/1.8 = 55hz The resonant frequency of the unmodified ET2 is roughly 3.5 – 5hz. Krebs argument is and I quote: Below this resonant frequency the cartridge is able to move the arms weight, start it and stop it, without cantilever deflection. He is wrong. This statement defies basic physics. Below 0.55hz the cantilever WILL deflect on an eccentric record. I assume he has misunderstood the explanation given to him by Frank Kuzma, and seems unable to comprehend this. |
The Kuzma looks like a nice arm, but one thing that always made me scratch my head is the air supply tube. We ET-2 owners pay so much attention to tonearm wire routing. What about that stiff plastic tubing on the Kuzma? It seems like it would have a huge effect on the arm's movement even if both of the fittings swiveled. Does anyone know any details about the tube's fittings or if it hinders the arm's movement? |
Hi Ct0517,
Yes, that Rockport Capella II is still my main turntable. When ready, the ET2.5 will be set on the brass armboard opposite to the Rockport 6000. Actually, you can see a bit of the ET at the left edge of that photo already, just that the whole counterweight assembly was not installed yet!
BTW, the Rockport 6000 can also be installed on nearly all turntables! |
DG - thanks for that info. Curious if Frank K happened to mention to you what his favourite tonearm was - of the ones he makes. |
Thekong
Actually, I have also fabricated a fixed counterweight for my ET2.5, but unfortunately have no time to test it yet. When it happens, the ET would be compared to my favorite arm, the Rockport 6000! Thekong – look forward to your impressions of the ET 2.5. Do you know what table it will be going on? I came across this pic in this other thread. Is this still your setup ? http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1301061425&openflup&16&4#16Very nice - btw Cheers |
Ct0517, At CES Franc K. mentioned a horizontal mass of around 100gm for Airline. He said that this worries some pivot arm guys, though in practice is "no big deal" w/r to LF performance. The Airline interests me as well-- incredible fit n' finish. I've read that one of its key advantages is very tight bearing clearance. At the high pressure necessary to float a "hard" captured air bearing of small surface area, this implies a low rate of airflow and thus relatively low turbulence and vibration.
Terminator can be mounted on pretty much any turnable. Porting the arm across turntables requires pedestals of varying heights to match the varying distance from a particular arm board to the top of the turntable mat. The pedestal can be ordered with an off-set stud mount that spins to accomodate any existing armboard hole vacated by any pivot arm. I made a DIY brass pedestal with this feature. |
Dover.
If the cartridge does not have a (damped) spring inside, please explain to us what causes the cantiliver to return to its rest position.
My discourse on resonant frequency IS the whole point, since the resonant frequency is set by the horizintal mass of the arm plus cartridge AND the cartridge's compliance.( plus some other complications around the systems overall rigidity) The system has a resultant resonant frequency which takes into account the stiffness of the cartridge's suspension. Below this resonant frequency the cartridge is able to move the arms weight, start it and stop it, without cantilever deflection. I do not need to talk to cartridge manufacturers to confirm this. Do the math.
Chris, I do not worry at all about playing eccentric records, nor do I worry about hanging my Shelter Harmony on the end of my arm. I have had one cartridge failure in 35 years of this hobby and this was caused by my son using it as a chisel to make a nice tangential groove on a record.( maybe he didn't like my choice in music) The other cartridges have simply faded away after long and fruitful lives.
While making some assumptions around the rigidity of the cantilever, wand and goose neck, my spring/weight analogy is valid.
Right at the start of my involvement in this thread, I said that my arm had been optimised for low compliance carts. Chris, in doing this I have compromised its versitility regarding cartridge selection. High compliance carts are out. Low compliance carts are individually adjusted using different counter weight shim washers.
I made this compromise in the pursuit of sonic performance. |
The ET2 gooseneck – the part that connects the armtube to the spindle is made from Carbon Fibre. I asked Bruce about making one in aluminum. It can be done in a special run if there is enough interest.
I told him I would find out how many are interested. If you have an interest you can contact me at
bcpguy(at)bell(dot)net
Cheers |
correction last post - I am in my 10th year now with the ET2's. When this thread started it was 9 years. lol. |
very interesting discussion guys. I am personally going on over 9 years with the ET2’s – never had a problem with a cartridge. I think I represent a typical music lover – meaning - I own xxxx records. At any one time there are xxx in 4 or 5 rows on the floor against the wall in my room that get cycled. Now none of them are eccentric enough to cause the spindle to move around like crazy. Most of the time I can barely see any movement in the spindle at all. I’d have to look really hard. Very interesting discussion on the various air bearings. It should be noted that of the ones mentioned so far , the Kuzma and ET2 I believe are the only two that can be mounted on any TT. There is the Terminator too (it seems from pictures/videos to occupy alot of space on the TT?) Maybe DG can elaborate? Its a BIG DEAL in my book to not be TT dependent. And fwiw - Any tonearm comparisons should be made imo mounted on the same table as this is a hobby about resonances and vibrations. So I have to ask here - Richard, Dover, Kong, others ..... what kind of records are you guys actually playing that you are so worried about eccentricity of the record ? I refer back to this post with data from the ET2 manual. http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1325551242&openflup&372&4#372Specifically the wording. This means that any given cartridge works against lower horizontal forces in the Model Two tonearm (.1 gram or less) compared to a conventional arm (.2 grams/gram vtf). These figures apply if you use records that are not severely out of round. If you like to play severely eccentric records, ones with runout of greater than 1/8”, then we suggest you use a low mass pivoted arm. --------------------------------------------------------------- Richardkrebs - We went on to talk about potential problems with cantiliver flex. His response was the resonant frequency due to the combination of a typical low compliance cartridge and horizontal effective mass was in the region of 2.5 -3.5 hz.(this has been published by them elsewhere), this is well above the 0.55 or 0.75 hz for 33 or 45 rpm eccentric records. Therefore the cartridge does not "see" this movement. Richard , so as shown above, Bruce has measured the lower horizontal forces in the Model Two tonearm (.1 gram or less) compared to a conventional arm (.2 grams/gram vtf). Are you able to get us the actual “lower horizontal force number” in the Kuzma Airline from Mr. Kuzma. I am very interested in this number – this is where the tire hits the road to me, no ? --------------------------------------------------------------- I have to admit something here to everyone as well, since I have been giving the discussions we have had thought. I really like the fact that the ET2 does not put any constraints on me as far as the type of cartridge I can play, anytime and anywhere. I can put on a Sonus Blue Gold with a single leaf spring, • Dynamic Compliance: 50 x 10-6cm/Dyne. • Tracking Force Range: 1.0 to 1.5 grams. than switch it over to a triple leaf spring beam with my XV1. Is this flexibility not worth something ? sorry for the following asterisks but this "IBM dos like" based forum does not allow for bolding and colors. *********************************************************** Is there another tonearm in existence that allows for the above to occur regardless of cost ? *********************************************************** btw - If I do find a record I like alot - that is so off centered (runout of greater than 1/8” as Bruce says) and cannot be replaced. Why not just drill out the center hole and use a heavy weight on it ? Richard/Dover/Slaw - is this not possible ? You guys have discussed drilling out of holes before.... Cheers |
Thekong Thanks for sharing your experience. I agree with Fremer. Thigpen does appear to hold patents on the decoupled counterweight. Whereas Walker uses a fixed counterweight at 45psi in the Proscenium, Richardkrebs advocates using a fixed counterweight, adding additional lead weights and running a relatively low pressure of only 12psi in his ET2. In my view his modifications increase inertia and increase the loading on the cantilever suspension when side forces from eccentric records are presented to the stylus. He employs no dampening to control this increased mass. Once it moves there is more induced cantilever flex from overshoot. This is way outside Bruce Thigpens original design concept of low mass and decoupled counterweight and should in no way be construed to be an ET2. There is always the risk of cartridge and or record damage with Richardkrebs added mass-low pressure approach. Richardkrebs advice in a previous post for those concerned about possible cartridge and record damage was, quote People are free to try, it is entirely their choice. Install an alternate cheap cartridge, play a record you don't like, if you are that worried about damage to same. This advice is probably about the only thing that Richardkrebs and I could agree on. |
Richardkrebs Referring to your last post 03-12-13: responding to Dover. At frequencies below resonance the cantilever is free to push the mass of the arm sideways. This does not defy physics, it is physics. Correct In other words the cartridge suspension is stiff enough to accelerate the arm mass sideways. . That is an assumption that will depend on the compliance of the cartridge. If the compliance is low enough then possibly, but before the acceleration commences the cantilever will flex. You seem to be unaware that cantilevers are mounted in a rubber elastomer that is not rigid. Think of a tension spring with a weight suspended at one end. This combination will have a resonant frequency. If you hold the spring end opposite to the weight and move it up and down at a frequency below resonance the weight will move up and down in sync with your movement. The spring will NOT stretch as a result of this movememt. . A curious analogy, yet again, you compare apples and oranges. Your analogy compares 1. Holding the end of a spring with a fixed weight on the other end to 2. The stylus point sitting in a groove, not held, at the end of a cantilevered beam, at the other end of which is a rubber suspension ( not a spring ), and the other side of the suspension has a mass loading that is constrained at 90 degrees by the rigid air bearing some 6 inches away. Your analogy is a triumph of the imagination to consider these two scenarios in the same manner. Your discourse on resonant frequency is irrelevant. Quite frankly I cant be bothered doing the maths, but I defy anyone to show me a cantilever that does not flex when playing an eccentric record. This does indeed defy physics unless you have a cantilever that has zero compliance. No, the video does not show the cantilever, that is why I asked him if it was a problem. If you agree the video does not show the cantilever then why do you repeat the following statement that is misleading? I repeat the video is shown specifically to allay fears of problems due to high horizontal mass. . I assume from your lack of response that you have not sought any advice on this matter from any cartridge designers. I would have thought this was the first port of call for a thorough and complete understanding of the problems of navigating eccentric records. |
Thekong
We look forward to reading your comments. |
It sounds better Hi Richard, I am no engineer, so has absolute no idea about the physics behind it. However, as Lloyd didn't use the decoupled counterweight (which is not hard nor costly to implement), I also believe it probably sounds better that way, at least to his, and apparently also to your, ears. Actually, I have also fabricated a fixed counterweight for my ET2.5, but unfortunately have no time to test it yet. When it happens, the ET would be compared to my favorite arm, the Rockport 6000! |
Thekong
I don't know how long patents last, but would suggest the reason that Lloyd does not decouple the counterweight is simple.
It sounds better. |
The Kuzma is unusual in its choice of bearing construction………… the use of porous material appears to be unique? In his review on the Kuzma Airline, Michael Fremer also mentioned that the Airline use porous material in the airbearing, while the older, but similar designed, Rockport 6000 utilized a groove-compensated bearing, which has lateral grooves in the bearing wall. He went on to comment that due to the difference in the bearing design, the much higher air-pressure used in the Airline didn’t necessary mean its bearing was stiffer. It is also interesting to note that the arm on the Walker Proscenium turntable shares a similar design with the ET2, but using a fixed counterweight and much higher pressure at 45psi. I believe Lloyd Walker is well known as a fanatic tweaker, who would not stop to squeeze out the last bit of performance from his turntable. So, why would he not use the decouple counterweight design (if he sees any advantage in it), or is that patented by ET? |
Dover.
You need to research the difference between the two air bearing types. The Kuzma is unusual in its choice of bearing construction. So how am I wrong in my statement that the use of porous material appears to be unique?
This in no way detracts from the ET2 bearing. I was just showing that other options are out there.
At frequencies below resonance the cantilever is free to push the mass of the arm sideways. This does not defy physics, it is physics. In other words the cartridge suspension is stiff enough to accelerate the arm mass sideways. Think of a tension spring with a weight suspended at one end. This combination will have a resonant frequency. If you hold the spring end opposite to the weight and move it up and down at a frequency below resonance the weight will move up and down in sync with your movement. The spring will NOT stretch as a result of this movememt.
No, the video does not show the cantilever, that is why I asked him if it was a problem. I have to take his word on this that it is not, and resonance formula back him up. Further this confirms what I see when my arm is tracking eccentric records. I repeat the video is shown specifically to allay fears of problems due to high horizontal mass.
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Richardkrebs I have queries regarding your claims re the Kuzma air bearing tonearm. This appears to be unique in using a porous material rather than multiple drilled holes like the ET. This is not correct. The ET has a captured air bearing with a continuous air gap between bearing spindle and manifold. We went on to talk about potential problems with cantiliver flex. His response was the resonant frequency due to the combination of a typical low compliance cartridge and horizontal effective mass was in the region of 2.5 -3.5 hz.(this has been published by them elsewhere), this is well above the 0.55 or 0.75 hz for 33 or 45 rpm eccentric records. Therefore the cartridge does not "see" this movement. This defies basic physics. Any lateral force on the stylus forces the cantilever to flex laterally, until the resistance of the cantilever to movement meets or exceeds that of the arm, at which point the arm must follow. More mass in the arm = more inertia in the arm = more flex in the cantilever. This Video was posted by them to allay fears of cartridge damage due to high horizontal mass.
This arm is amongst the best currently available. It has a large differential between its vert and horizontal effective mass figures and does not appear to be a cartridge killer. The video does not show the cantilever. Proof of the above assertions is not demonstrated. As regards the best available, what other arms have you auditioned to draw this conclusion. If you are talking air bearing arms - where have you considered the dynamic stiffness of the air bearing. Although the Kuzma runs 60psi into porous tube versus the ET2 at 19psi into captured air bearing, the psi alone does not determine the dynamic stiffness. Some other factors you need to consider are : The hole sizes The flow of air The surface area of the bearing etc The ET2 also has a wider manifold. If we assume for arguments sake the air bearings are of equal dynamic stiffness, the ET2 will be inherently more stable than the Kuzma. He assures me that there is no problem with the cantilever under these extreme circumstances. This is an inadequate response. To support your contention that adding mass has no deleterious effect, which cartridge designers have you sought an opinion as to loading up the cantilever in the manner you continue to advocate in this thread ? Bruce Thigpen's patents clearly outline the benefits of the decoupled counterweight and lower mass. |
I have been researching possible bearings for a new Arm and I came across the Kuzma web site and the Airline Arm. This appears to be unique in using a porous material rather than multiple drilled holes like the ET. It also has a sliding sleeve instead of the sliding spindle of the ET
Wow this is a spectacular looking arm which is definately on my wish list.
This brings me to the subject of horizontal effective mass again. I asked them for this figure for the Airline. It is probably not appropriate for me to publish this here, since it was a private conversation and the number is not shown in their specs. But I can say that it is higher than my heavy modified ET2 arm. We went on to talk about potential problems with cantiliver flex. His response was the resonant frequency due to the combination of a typical low compliance cartridge and horizontal effective mass was in the region of 2.5 -3.5 hz.(this has been published by them elsewhere), this is well above the 0.55 or 0.75 hz for 33 or 45 rpm eccentric records. Therefore the cartridge does not "see" this movement.
He directed me to a video of the arm and cartridge tracking the lead out grooves with a oscillation amplitude of 12mm. See www.Kuzma.si ,tech support,tech info, Airline video.
This Video was posted by them to allay fears of cartridge damage due to high horizontal mass.
This arm is amongst the best currently available. It has a large differential between its vert and horizontal effective mass figures and does not appear to be a cartridge killer.
I'm sure you will agree that this motion is violent and way beyond what any record eccentricity would produce. He assures me that there is no problem with the cantilever under these extreme circumstances.
I want one.
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For clarity: the question in my last post was addressed to Mr Dover. |
Can you please advise (and of course fellow posters) what speakers you were using in your system when you set up the loose counterweight decoupling method.
I am interested in this approach and its effect on the sound, particularly in the bass region. Thank you. |
The base of the ET2 is mounted with one bolt and has 3 grub screw spikes for proper leveling on any surface or armboard.
We have discussed removing the aluminium shim. If your worried about marring your surface, Dover had mentioned filing down the grub screw points.
Can the bracket be improved or .......removed...? Another material? It is the part that holds all of the goods.
Cheers |
Yes when you talk to Dover and I you are conversing with the future. Richard/Dover – have you figured out a way to tell me how the stock markets will open in Toronto or New York ? Small correction to my previous post. humidity is good I have found for vinyl (as we deal with static), but not good for ESL’s especially my Quads which are very sensitive to levels. They like it really dry. So its like being between a rock and a hard place in a way. Still Quad 57 and 63 are designed differently. Some info I got from a respected rebuilder - The 63 panels will be destroyed soon if placed in rooms with high humidity. Not as hardy as the 57’s – now there’s an oxymoron for you. The Acoustats do not seem affected by humidity – are they like Hercules of ESL’s ? Both in their ability to withstand conditions over time and accept wattage without problems. Wondering if this is due to the amount of space between the mylar? Cheers |
Chris, the good thing is, if we have a bad day over here we can fly over to your place and start the day again ... |
Chris
Yes when you talk to Dover and I you are conversing with the future.
I agree with you. Clean power and I think that we should not underestimate the effect of our own state of mind.
I think that every professional reviewer should prefix their review with...,
Today I feel..., or over the period of this review this was my general state of mind.
BTs comments are interesting. I know the effect of the shims and grub screws. It is definitely positive. As in the drive thread, I believe that there should be nothing soft in the loop between LP around to cartridge. The o'rings are quite soft.
My testing, with and without the bearing sleeve clamped seems to support that view. |
RichardKrebs
To everyone..I'm sure that you have experienced this. Last night's listening was great. All the planets seemed to align. So what causes this? Clean power? Just the right room temp, humidity? My own state of mind? Off topic, I know, but I am curious to read your views on this. Richard your NZ last night is my yesterday still.... I believe in the one and almighty, and in the things that are out of my control. He giveth and taketh away. Yes I am talking about the local hydro company. This is an audio gear site. I was very aware of the power limitations I had, and their effect on my systems in the big dense city. I feel kind of blessed now that I live in a rural area with an abundance of clean, raw power. Sometimes on a few occasions there is not enough (hot humid july/aug nights). Other nights, more often, there is too much above 120v. When the number on the gauge reads between a certain range I have come to know that good things can happen. It then depends on my own mood. Humidity helps. There is more grain in the music for me when the power reads above 120v. Looking forward to converting my table to battery soon. All Power Conditioners I have tried made the bears sound pleasant but like they were on meds. No thank you for the amps. The OTL's coming have their own line conditioners designed for them. |
Chris -
No I dont have the equipment, but Martin Colloms did in a Hifi News review years ago ( 1985, I think ). He measured the resonances before and after the air bearing and compared them to ascertain how the air bearing dealt with such. Typically you would use an accelerometer placed on either the arm or bearing housing to measure these.
If my memory serves me well the resonance profile remained in tact, in other words even though the resonance is passing through air and rubber, it went through almost unhindered.
By the way - another little tweak for you - I decoupled the rotating arm lift from its bracket using teflon washers/spacers, another small audible improvement. |
Here is Bruce's opinion on using ET2 manifold shims
On 3/5/2013 10:05 AM,
Hi Bruce
We would like your opinion on the small space between the ends of the manifold and the rubber rings.
You can slide the edge of a piece of paper in there.
Is it by design for resonance control - to achieve a certain frequency ?
If shims are inserted in there - does this not in theory make the setup more rigid - desirable?
Would this affect the general frequency resonances of the ET2?
We look forward to your opinion on this. thanks. Chris
Chris,
The o-ring is used as a seal, when the manifold is inserted, the ring is flattened and the gap is taken up, that is the design intent.
The science of resonance in a phonograph tonearm would first involve a measurement to prove something exists. This is very easy, Take another ET2 tonearm and use its cartridge to play the tonearm under test. Compare the levels of record playback to the measured level of vibration on the tonearm under test using a spectrum analyzer. If the vibration levels measured are greater than -50dB below playback levels then there may be something significant and you might call it a resonance.
Odds are good that the manifold has no significant vibration levels from a stylus forcing function while playing a record. I hope this helps.
brucet
Richard, Dover, others ? When Bruce says: “science of resonance in a phonograph tonearm would first involve a measurement to prove something exists.” Curious if magnetic and mass damping, and any of its effects can be measured other than just by listening ? Have you done it? |
Hi Frogman,
Thanks for the feedback. You have highlighted the nub of the issue in your last few sentences - when the arm moves laterally to accommodate eccentric records it becomes very complex. In addition to the bearing tube moving back and forth we have -
1. The arm mass pushing the cantilever back and forth through its pivot point
2. The counterweight, if partially decoupled with a spring, starts to oscillate as the bearing tube moves back and forth.
My approach to the problem has 3 elements all of which work together -
1. Lighten the arm to minimize resistance to lateral movement. Remove any soft spongy material - shrink wrap/foam if using the old aluminum arm tube.
2. TOTALLY decouple the counterweight ( no spring, no fixed coupling )
3. Minimal magnetic damping
Counterweight Set Up
In my view fixed, coupled counterweight is wrong because it adds inertia, a resistance to any correction for eccentric records.
I also think a spring is suboptimal, because although by tuning it we get a lower resistance, and maybe better bottom end on round records, on eccentric records the in and out motion means the counterweight will oscillate and feed back into the bearing tube, affecting its horizontal stability.
I would surmise that when you tune the spring, you are probably synchronizing the motion of the counterweight with the arm motion to minimise these conflicting forces. This will vary with the cartridge compliance and how eccentric the record is.
With both coupling and spring ( partial coupling ) the arm movement is inhibited – causing cantilever flex that is disconsonant with the music.
The key question is - What do we want the counterweight to do on eccentric records ?
The answer in my view is nothing.
We want it to continue to load the tracking force.
We want it to remain absolutely still horizontally whilst the arm moves in and out so it does not inhibit the arm movement. ( we don’t want the tail wagging the dog ).
Think of a hinged counterweight, rigid vertically, but free to move so that when the arm moves the counterweight stays still.
My solution was to remove the spring action by loosening off the end cap such that the counterweight beam just flopped at a touch; then inserted teflon wedges loosely either side of the spring to provide the tiniest dampening of that I could apply.
The combination of the "floppy" counterweight in the horizontal direction and minimal magnetic dampening gave me the best result – very quick bottom end.
A bass drum has harmonics and overtones up in to the high frequencies – the highs tell you how a drum is hit – so for me I trade off a little bottom end weight for accurate, clean and extended high frequencies.
Funnily enough this approach gives me the quickest and most tuneful bass.
How much magnetic damping to apply ?
My experience is as little as possible. What I have found is that I set the amount effectively by tuning the bass for optimum speed. Remember that the eccentric arm movement is affecting all frequencies. The dampening will affect all frequencies.
My view is that if you use too much magnetic dampening you will stiffen up the bottom end, but at a cost over over dampening the high frequencies. That’s why I was interested in Chris testing the eddy clamp – which I suspect is just too much.
I wanted to clarify that for me the use of minimal magnetic damping goes hand in hand with how I set the counterweight up and the low mass/minimal resistance.
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Frogman.
I enjoyed your post, thankyou. How much blutac did you add to the headshell? By way of comparison I have added a net 0.77gm to the headshell of the ET2. (Lead in, teflon out.) Not a lot of extra weight.
On damping... If it is not meant to move, make sure it doesn't.
To everyone..I'm sure that you have experienced this. Last night's listening was great. All the planets seemed to align. So what causes this? Clean power? Just the right room temp, humidity? My own state of mind? Off topic, I know, but I am curious to read your views on this.
thanks
Richard. |
Thank you Chris, Dover, Richard, and all for the fascinating data, opinions, and food for thought. I continue to enjoy the, admittedly, subtle effects of using a single weak magnet with my ET.
I can't claim to understand the physics involved well enough to give a thorough explanation of what happened in my particular case, but I have to concur with Dover about the concerns over added mass. In my case, it was not mass in the spindle, but a case of too much mass at the "headshell" and cartridge itself. A few years ago I managed to destroy the suspension on one of my VDH cartridges by applying too many bits of Blu-tac to a "naked" MC1, and to the top of the headshell in an attempt to dampen a cartridge that sounded overly aggressive in the highs. It worked to smooth out the ragged highs, but within days, experienced a collapsed suspension. The cartridge was properly balanced and setup at the appropriate VTF.
****Does damping not mean - reduce, diminish, dull - to a point that reduces some of “vinyl’s nasties”, caused mostly in this case with the ET2 tonearm – the off center hole - but we want to do this without taking away too much from the music itself ?**** -Chris
In the endless debate about wether footers, pads, etc. have a beneficial effect on music playback accuracy, I have always contended that, in absolute terms, it is not possible to overdamp a component's resonances by adding mass. Added mass can only be a good thing; in theory. While it may be possible to tweak the resonances to suit a particular system or listener's tastes, eliminating/controlling resonances can only be a good thing for a component's electrical performance, if not it's role in a given "system" (including the listener's ears) which is functioning in the electrical domain. But, it seems to me that in the case of a tonearm, we are not talking about simple resonances, but how added or removed mass affects the movement and stability-in-motion of the arm/cantilever "system". Sorry for possibly stating the obvious, but it helps me to make better sense of all this. Thanks again for a most interesting discussion. |
“para 1 - not obvious to everyone.”
Why not, there are only 2 words to understand: ‘modified ET2.’
“Adding lead mass creates higher inertia but does NOT retard motion.”
Yes it does, more energy is required to activate the system.
You’re banging on about lead mass and inertia as though it is a random activity.
Required mass (and its related inertia) will be cartridge specific, so isn’t it simplistic to state or imply that no mass should be added to an ET. |
Dover
As you said we will never agree on this.
The difference is that I have tried both light and heavy ETs. As far as I can tell, I am the only one who has done that. If so, I am the only person here who can speak with any authority on the subject.
People are free to try, it is entirely their choice. Install an alternate cheap cartridge, play a record you don't like, if you are that worried about damage to same. Your scaremongering may have dissuaded people from trying a simple reversible mod, which is a pity since we could have advanced the collective knowledge of this diverse group. And isn't that exactly what these forums are for? |
Hi Chris - Yes I have a good memory. When we first imported a pile of ET2's we had in the shop an ET1. There was a big debate at the time that the ET2 had less bottom end than the ET1. The ET1 has a fixed counterweight. My business partner preferred the counterweight bolted up as per the ET1, but I found that gave a one note bottom end, lacking speed and articulation.
I experimented with the counterweight coupling and other ET2 mods quite extensively not only with a variety of TT's including Sota Star Vacuum, Townsend Rock, Roksan, Oracle and Final Audio TT, but also a variety of speakers including Martin Logan CLS, Apogees, Proac EBS, Proac Tablettes, Duntech's, vintage Tannoy Monitor Golds and many others - over the last 30 years.
Also have run the ET2 specifically with a wide variety of cartridges including Madrigal Carnegie, various Koetsu's, Van den hul Grashopper, Shinnon Red, Sumiko Talismans/Virtuoso's, Shure V15VMR, Denon 103 Garrott, Benz Reference and many others I've long forgotten.
I have also seen enough off centre cantilevers to last a lifetime from the misapplication of both tangential and pivoted arms.
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Richardkrebs para 1 - not obvious to everyone. You are testing the effect of magnetic damping with an ET2 with rigid counterweight and high mass. Chris has been testing magnetic damping with partially decoupled counterweight and no added mass as has Frogman. I have not said that mass, mag damping and fluid damping are the same other than that they all resist motion and that this resistance increass with frequency. This simplistic view fails to differentiate between inertia and damping of motion. During the course of this debate over the last few weeks you dont seem to comprehend the difference between inertia and damping of motion. Inertia is the resistance to a change in its state of motion or rest. When you add lead to your ET tonearm you increase inertia. By increasing inertia the cantilever will flex more on eccentric records. Damping is the retardation of motion once the movement has commenced. This means the cartridge can move straight away with an eccentric record, which results in minimal flex in the cantilever, and less distortion, but eddy currents generated by the motion of the arm relative to the magnet retards the oscillation of the arm and cartridge. Adding lead mass creates higher inertia but does NOT retard motion. Magnetic dampening has lower inertia and dampens motion. I repeat again that the lead mass that you have added puts more load on the cantilever when the arm tries to move to accommodate an eccentric record. Furthermore, with the higher mass of the added lead, when the arm moves there is more momentum, there is no control over this mass, and there is no damping of motion to minimize overshoot as the arm tries to correct. As viewed by the cantilever this is no different to me adding mass in the linear plane to the ET. Again - a very simplistic view of the world. Pivoted arms have tracking error and offset angle. The physics is quite different to that of a linear arm. Adding mass but Morch with their flywheel do not appear to have reached that point nor have I with my arm. This is an assumption and speculative. I could just as easily surmise that the Morch arm is so thin and lacking in structural integrity that it needs added mass and fluid dampening to control energy and resonances in the arm generated by a good moving coil cartridge. Conventional mathematics says that adding mass to a flywheel, not only increases inertia, but it is harder to slow down. You are making the problem of navigating an eccentric record bigger than it needs to be. |
Dover – I really do wish you had your ET2 up and running. The detail you remember is impressive.
Richard - that was a really nice post on your findings.
Thank you for taking the time to do this. Your attention to detail is very evident as well. BTW - Your recommendation for the ground on my second regulator has helped - thank you.
Also I found the “Why do we listen to music” on your website very informative. No affiliation to you or your site.
I want to ask (anyone) when we talk about dampening ....
Does damping not mean - reduce, diminish, dull - to a point that reduces some of “vinyl’s nasties”, caused mostly in this case with the ET2 tonearm – the off center hole - but we want to do this without taking away too much from the music itself ?
The effects of the magnets (small ones) so far to me is very subtle. Have not tried stronger neo magnets. I am not able to put magnets at both end of the manifold as my ET2 is on a pillar that only allows magnets at one end.
Is the effect of the magnets in my case subtle because, imo, I do not play really eccentric records. Or does the small amount of movement we are talking about even matter ?
Richard/Dover - would not significant movement in the ET2 spindle be required, to induce more than a subtle effect with eddy currents when using smaller magnets as I have been using on a stock spindle ?
I will say it can sound a little “nicer’ sometimes with the magnets on some lps. Lps are engineered all differently. On others the effect is very small if at all. There however seems to be more background/ambient info without magnets on those lps that I did notice a difference. I refer back to the car shock absorber analogy.
So does this not imply - trying to get the setup done right first - before you add any kind of dampening effect - even the oil trough ?
IMO - The good thing here is any ET2 owner can try these magnets very easily and decide for themselves. Hope we get more impressions from others.
I got a response back from Bruce that he is travelling. I did ask him about the manifold shims, and will also ask about his opinion on adding weight in the spindle itself - even if only 30 gms.
Very intriguing |
Dover please re read my opening sentence.
"I have finished testing Dover's mag configuration on my modified ET2"
This clearly states that my ET is modified as anyone reading this thread recently would know. My testing was done in that context. That fact is obvious. The Dover Mag dampening test was as you proposed to Chris and that he asked me to try. I also took the opportunity to revisit earlier versions with strong and weak magnets independantly each end.
I have not said that mass, mag dampening and fluid dampening are the same other than that they all resist motion and that this resistance increass with frequency.
The Morch adds what appears to be considerable mass at a radius out from the pivot point. In so doing they have made a flywheel. Lateral movement of the cantilever mounted on a pivoted arm tries to rotate the arm about this pivot point. This added mass, flywheel, serves to resist this rotation tending to keep the cartridge still, a desirable trait. As viewed by the cantilever this is no different to me adding mass in the linear plane to the ET. Adding too much mass would result in unwanted cantilever movement due to record hole out of center problems. We agree on this, as you say it would load up the cantilever, but Morch with their flywheel do not appear to have reached that point nor have I with my arm. |
Richardkrebs, I have finished testing Dover's mag configuration on my modified ET2 For the record you have NOT tested my ( Dover's ) configuration at all. You have only tested magnetic dampening in the context of your own reconfigured version of the ET2. Your added lead mass has pushed the operating parameters of your ET2 outside of the original design. Your ET2 is set up completely differently to mine in that : You have rigidly coupled the counterweight to the arm. You have added lead mass to your bearing tube. You have added lead mass to the headshell. You have increased the horizontal mass significantly over the standard arm. The configuration I use is: Decoupled counterweight in the horizontal mode ( spring bypassed ) Lightened tonearm Minimal magnetic dampening The level of actual magnetic dampening I use is as follows : Shure V15VMR - 1 cupboard door magnet under the bearing tube at counterweight end Koetsu Black - 1 cupboard door magnet as above Madrigal Carnegie Model One - 1 cupboard door magnet as above Denon 103 Garrott ( Aluminium/Boron hybrid cantilever/Weinz Parabolic diamond ) - none Yet again, and you seem to do this with monotonous regularity, you misrepresent statements and arguments in order to justify your own point of view. For those of you who may be interested in adding mass. I would bring your attention to Morch's latest arm which uses massive weights to increase horizontal mass. On their web site it does not say what these weights are made out of, but brass or stainless steel would be reasonable asumptions. Extra weight like this would dwarf the 30 or so grams I have added to my ET. Your argument is wrong. The Morch arm is a pivoted tonearm. The ET2 is an airbearing tangential arm. The Morch applies its mass at the rotational pivot point. You have added lead mass to your ET2 at 3 points - the headshell, the bearing tube and the counterweight. One needs to understand the physics as it applies to Linear Dynamics versus Rotational Dynamics. The added mass under these different conditions will have quantitatively different outcomes. You don't appear to have considered this at all. Furthermore, the Morch website confirms my earlier statement that added mass, magnetic dampening and fluid dampening are not the same yet you contend that they are. Morch state on their website that mass increases inertia and has no dampening properties as I explained to you earlier. Morch use silicon fluid to dampen the motion in addition the added mass weights, again, which only increase inertia. Your earlier contention that added lead mass is the same as fluid or magnetic dampening is incorrect. Again I caution readers that adding lead mass in the manner advocated by Richardkrebs could potentially lead to cartridge and record damage when playing most records which are eccentric. Why ? Because the added lead mass is loading up the cantilever. |
I have finished testing Dover's mag configuration on my modified ET2, along with individual mags independantly at either end. This has been the most extensive test I have done with magnets, spanning 3 nights of listening. The results were consistent and largely the same for all mag configurations. Differences being the degree of change. I used both weak fridge magnets and what I believe to be strong neo magnets.
Test records were..
Corelli, Harmonia Mundi 7014, track 1
Oscar Peterson Trio, We get requests, Analogue productions V/V6-8606 track, You look good to me.
Saint-Saens, Respighi, Proprius 7857, track 3
The descriptions here are all referenced to no magnents, being the control example. All changes noted were minor but repeatable over the three nights and were present with both magnet strenghts.
With the magnets in this is what I heard....
Corelli. The harpsichord notes lost some of their attach. The spaces between the individual instruments of the orchestra was reduced with the sound stage being compressed laterally and front to back. The piece begins with a series of very short movements, each stopping abruptly allowing the sound to decay naturally into the hall. The tail of this decay was shortened.
Oscar Peterson. This track begins with a bowed bass followed by the piano and drums, it steadily builds to become quite loud by track end. The effect is dramatic. The bowed bass had less bite. Less slip stick of the bow on the strings. Ray Browns usual muttering as he plays is less apparent. Less space between instruments and smaller sound stage. The build up to the final notes was diminished.
Saint-Saens. The singer uses vibrato to good effect adding interest to this piece. This vibrato was rounded, smearing her voice. An aside is the airconditioning that can be heard on this track. It rumbles along beneath her voice. With the mags in place this becomes more of a low frequency hum. Sound stage and hall cues were diminished.
With all iterations, there was a fog added, this covered up low level detail. There was also a slight feeling of unease, a tension which by the third night had become annoying.
The greatest negative change was with the 4 strong magnets, becoming less of a problem as I reduced strength and number.
All of these differences were slight, but it is the litle bits that make this hobby of ours interesting.
For those of you who may be interested in adding mass. I would bring your attention to Morch's latest arm which uses massive weights to increase horizontal mass. On their web site it does not say what these weights are made out of, but brass or stainless steel would be reasonable asumptions. Extra weight like this would dwarf the 30 or so grams I have added to my ET.
An appology. Some of you have contacted me via my Technics upgrade web page krebsupgrade.com While I can see the mail, I cannot at this time open them or send replies. I will get it fixed asap.
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I reached out to Bruce to get his opinion about the shims idea for the manifold. Look forward to his response and will post back what he says.
Cheers |
Dover/Richard/Frogman and others trying the magnets.
Another short listening session today then I had to head out for the evening. My impressions are mixed now. Not sure what to think. I really feel with myself, when tweaking like this what I can hear can depend alot on my mood going in, and how the day went. This is why multiple sessions are required for me over time. I have added more magnet slivers (4) to each side. Will have a few more listening sessions this week.
Richard/Dover
I used to enjoy “shagging” fly balls during practice playing baseball when I was younger.
Cheers |
Chris.
Shagging is something done here in NZ between consenting adults. |
Ketchup
When you had your three magnets in a row, did you notice any difference in sound as a record side progressed? Ketchup – the way I used the three magnets in a row the effect was very subtle, so too hard to answer the question sorry. In a tower three on top of one another the effect is more noticeable in system. My spindle is sitting high compared to where the magnets are when in a row. I will say lack of knowledge about the magnets prevented me from experimenting further. The discussion here and the experience with the Dynavector arm made me want to experiment. |
