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High compliance cartridge on a heavy arm...

Discussion in 'Turntables' started by nickrobotron, Jul 18, 2011.

  1. nickrobotron

    nickrobotron una bella tazza di caffe Subscriber

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    Should I track on the heavier side or the lighter side?

    I just dedicated this evening to aligning my M91ED as perfectly as I could. Now I'm trying to decide on tracking weight. The TP-16 is around 16 grams. My immediate thought was to go heavy, but I was wondering if this is dangerous for the stylus. I was also wondering if the new replacement stylus changes things. Is it lower compliance than the original stylus?

    I was doing research on cartridge/tone arm matching for the first time tonight. I'm really trying to figure it out. I've learned that tonearms < 12 grams would be considered low mass, 12-20 grams would be medium mass, and > 20 would be high mass. Is this correct?

    I've gathered that it's pretty easy to find the mass of a particular tonearm that you're working with, but it's hard to determine the compliance level of the cartridge. What is this measured in?

    I've read on here that the NOS Ortofon FF15XE MkII I picked up this weekend is a better match for my arm. How do people find out the "compliance level" (if that's the right term) of these cartridges? Is it just based on the recommended tracking force?

    Nick
     

     

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  2. catman

    catman Addicted Member

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    G'day mate, this is an interesting one. Ideally a high compliance cartridge does not mate well with a 'massy' tonearm, however the real world sometimes tends to blur these rules!

    I have seen high compliance cartridges come out of the factory mated with quite 'massy' tonearms....so I don't know!

    In any case I would use the recommended tracking weight (1.25 grams is fine). See how you go and let us know your findings and observations. Regards, Felix aka catman.
     
  3. melofelo

    melofelo Addicted Member

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    very generally speaking..i'd put low mass <10gm ..medium mass 10 - 16gm..and high mass >16gm..
     
  4. nickrobotron

    nickrobotron una bella tazza di caffe Subscriber

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    I went with my gut instinct. I am tracking at 1.75 grams right now.

    I think my observations anywhere from 1 gram to 2 grams would be similar. I think it sounds good tracked at 1.25 and 2 grams. I'm not noticing a difference. I'm listening to Paul Simon's Still Crazy After All These Years (an album full of minor details) and I am experiencing all the shakers, bells, background vocals, string sections, etc. all the same.
     
  5. nickrobotron

    nickrobotron una bella tazza di caffe Subscriber

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    Good to know. So my arm is on the heavy side for a medium mass arm?
     
    Last edited: Jul 18, 2011
  6. day67

    day67 Super Member

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    I'm always confused about this. I know it's "high compliance cart -to-- low mass arm" generally and visa versa. But what makes it a high or low compliance cart? Layman's terms please. And is the recommended vtf provided by the maker an indicator as to the cart's higher or lower degree of compliance? Scratch, scratch
     

     

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  7. DougMac

    DougMac Super Member

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    The cantilever has to be suspended. The "stiffness" of the suspension is compliance. You might find this helpful.
     
  8. bhundu

    bhundu Addicted Member

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    Search "compliance calculator". I'd guess you are fine where you are. My TD-160 came with a M91ED. When it's used I do track a little higher on the original stylus at 1.5g though.

    To the collective, I understand that bad matching will result in an unacceptable "Resonant Frequency". I understand this to be a resonant vibration on certain sections of the groove due to the nature of the stylus suspension and arm mass? Is this accurate?

    Also are these RFs discouraged due to audible effects or groove damage or both?

    Like the OP I have been using higher compliance carts on the 16.5g arm than would seem matchworthy with a compliance calculator, but haven't experienced any negative results.
     
  9. melofelo

    melofelo Addicted Member

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    compliance is a measure of how springy the suspension is...
    so a high compliance cartridge has a fairly soft suspension...ie the suspension is easily compressed, it is highly complaint
    ... if you stick a high compliance cartridge on to a high mass arm..it will generally work...but tracking anything other than a perfectly flat record will cause undamped vibrations in the arm because the suspension is too soft to recover after a warp...or while tracking heavily modulated grooves of high amplitude waves
    those vibrations wil affect the stylus' ability to trace the record groove properly..and unwanted resonances may intrude upon the audible frequencies caused by this mis match...
    think of a heavy car on soft suspension springs...when it goes over a bump..it wobbles for a long period of time before it comes to rest...

    the opposite applies for a low complaince cartridge and a low mass arm... the low compliance of the cantilver's suspension (e.g. fairly rigid, does not deflect much under a light mass) added to a low mass arm...(eg less inertia..so requires less force to move it) will lead to mistracking and in some cases an inability to correctly follow a record that is anything other than perfectly flat... also the stylus will struggle to follow the groove without moving the whole arm as well on large modulations in the record...ie bass notes..
    same car analogy... light car on stiff springs...meets bump... the car will spend most of its time off the ground when it hits a bump at speed...and the tyres will have trouble following the up and downs of the roads surface because there is not enough mass acting on the stiff suspension ..

    its basically a juggling act and you can get away with fairly extreme combinations but ideally you want to settle for a decent mechanical match between the mass of your arm..and how soft or stiff the suspension in your cartridge is...

    the effective mass is the mass that the cartridge 'see's at the end of the tonearm... some arms are heavier in 'mass' but concentrate that mass near the pivot so the end of the tonearm may have a lower effective mass acting upon the stylus.... think of tapered tonearms...where the mass increases towards the pivot...or arms with heavy bearing assemblies that use a thin tonearm tube...

    the balance you aim for basically..is to keep the stylus moving as independently from the arm as possible..without causing any vibration that will feed into the arm and back into the cartridge...ie wobbling... on the other side...you want the stylus to follow the groove as closely as possible without being disturbed (vibrated unecessarily)by warps in the record or losing contact with the groove walls..
     
    Last edited: Jul 18, 2011
  10. gusten

    gusten Addicted Member

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    One can say that records are not perfect, investigations have shown that resonances are always present, but not with so high amplitude that we can see them. It means that the output at low frequences is higher than that it should be (woofer pumping), it also means that VTF is varying depending on how much the tonearm is resonating. When we actually see the arm resonating the span in VTF could be from very high to zero, that is why we can have mistracking, there is no VTF present.

    The thing that can take care of rather large mismatches is tonearm damping. Damping the tonearm´s movements is a key in getting better low frequency stability.
    gusten
     
    Last edited: Jul 18, 2011
  11. bhundu

    bhundu Addicted Member

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    "When we actually see the arm resonating the span in VTF could be from very to zero, that is why we can have mistracking, there is no VTF present."

    I'm imagining the stylus from front on. Is it bouncing off the left and right hand walls of the groove due to resonance to such an extent that because of the angular groove walls it has an opposing force that negates (or exceeds) TF? On poorly mismatched set ups?
     

     

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  12. dlaloum

    dlaloum Super Member

    Hi Bhundu, Nick

    any sprung system will have a resonance point at which it moves most easily - energy will tend to get channeled into that frequency resulting in a peak in amplitude.

    The mass/springing system of the tonearm, where the only spring is the suspension of the cartridge works in the same way.

    Even when the resonant frequency is at the "ideal" frequency of 10Hz, what happens is anything near that frequency will tend to excite the sprung system, and magnify those frequencies.

    Test records have tracks of low frequency sweeps - basically a tone at a set level with gradually dropping or increasing frequency usually starting at 3 or 5 Hz and rising to 20Hz or 25Hz.

    If you record this track and plot the amplitude to frequency, you will note that it does not reflect a line (as it theoretically should) but shows a marked peak at the resonant frequency. Depending on the arm/cartridge this peak can be anywhere from 2-3db (ok) up to 8db+ (bad).

    The peak is not a narrow one, and usually influences frequencies on either side of the maximum point to a lesser extent.

    As the RF (resonant frequency) rises it can start to impact on the audible low frequency response of the system - a substantial boost in amplitude at 15Hz as an example can cause huge subwoofer/woofer pumping, sucking up amplifier current, causing intermodulation of the bass frequencies, and generally affecting the sound as a result. (amps being under pressure using up all its grunt moving the woofers ends up losing its sweetness in the high end...) This is one of the reasons golden age phono centric amps often have a subsonic filter!

    As the RF drops it starts to approach the frequencies generated by things like footfalls, and other vibrations external to the TT.

    If you watch an arm/cartridge at its resonant frequency it clearly starts to "wobble" - there is substantial physical movement.. as it rises the needle will get pulled slightly back, as it drops it will get pushed slightly forward, a form of wow that is seldom considered, but does affect all frequencies reproduced.

    Additionally the movement generates vibrations in the entire system which in turn intermodulate with the signal, generating other spurious "noise" (Intermodulation Distortion).

    Also when the RF is triggered, the cartridge movement can cause mistracking - with all of its associated problems, including increased wear and tear on record and stylus!

    A well tuned arm/cartridge have the RF positioned where it does the least harm - by keeping it away from footfall/external vibration frequencies, and the resonant frequencies of the TT suspension (usually around 5Hz), keeping it away from the audio range (15Hz+) and if possible keeping its amplitude as small as possible.

    Regardless of the final RF, the resonance remains an undesirable aspect of TT technology.

    There is a way to control it, it is called damping. Damping can 1) reduce the amplitude of the RF, and 2) slightly shift the peak frequency.
    The most common damping is fluid damping using a paddle system in an oil bath attached to the arm - it provides a slight resistance in a frequency sensitive way - the end result can be very effective. (the damping can be internal within the tonearm pivot column, external, it can be done with fluid or electro magnetic servo means...)

    As an example, my JVC turntable has a damped arm - running a TK9e cartridge, I measured the resonant frequency at 5.9Hz - this being with the damping disabled.
    Enabling the damping "widened" the peak somewhat - going from 5.8Hz to 6.5Hz, but dropped its peak from +4db down to +1db.
    The stylus compliance is 31cu, the arm mass calculated out to 23.8g (including cartridge and fixings) - so high mass arm with high compliance cartridge - resulting in low RF (much too low).

    With damping disabled - the mistracking was relatively obvious - and the system was very very sensitive to anyone walking around the house.
    With damping enabled - the mistracking disappeared, and footfall sensitivity although still there, became much much reduced.

    This is clearly NOT an ideal setup - I can make it useable with damping - but it will be better if I can lighten the mass by 4g or 5g with a lighter headshell.
    And then I can still damp the resulting higher RF....

    Some test records have an interesting track that can be used to identify the RF they run the low frequency sweep tone, at the same time as a steady audible tone...

    When the arm hits the resonant frequency you clearly hear the tone "warble" - a result of the arm/cartridge movement.

    A lesser and more subtle version of this happens when you play a record, and the arm is excited at its RF.

    Here is a usefull calculator for working out Effective Tonearm Mass http://www.luckydog.demon.co.uk/images/EMC.XLS

    It requires weighing different components of the arm, but provides a relatively accurate figure for real life effective mass, which is useful in working these things out, as opposed to very vague light-med-heavy categories and manufacturer arm specs that can be out substantially based on what fixings, headshell and cartridge you are using at the time.

    I strongly recommend damped tonearms regardless of the RF.... and for undamped tonearms, the Shure styli with the damping brush is a very effective alternative too...

    Some of the top arms that are "undamped" have a touch of friction in the way the bearings are set up and lubricated that provides a bit of damping - this is one of the reasons some apparently less than ideal combinations work well!
    (some people tweak their arms by using a slightly thicker lubricant to provide a touch of damping too...)

    bye for now

    David
     
  13. bhundu

    bhundu Addicted Member

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    Not to thread hijack but while Melofelo and Guste are here, what are your thoughts on dynamically balanced arms like the TP-16mk1? Are they more forgiving on cart matching due to the spring based TF?
     
  14. bhundu

    bhundu Addicted Member

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    Excellent notes David. Thank you.
     
  15. gusten

    gusten Addicted Member

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    As it is the eff. mass of the tonearm and the spring constant of the stylus´ suspension that are involved in the resonance I cannot see how the VTF is applied matters. If these arms are more forgiving it has most likely to do with how the bearings work. With some friction, preferably with high viscosity grease present, it will help in damping.
    gusten
     
  16. gusten

    gusten Addicted Member

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    If lateral resonance present, can be so. But a vertical resonance might also be present, so when the arm is bouncing up and down, at some point there is no VTF left for tracking.
    gusten
     

     

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  17. melofelo

    melofelo Addicted Member

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    if i recall..the ultra low mass arm on my first turntable ( a dual cs 505/II ) was rather good in operation. It did use a high compliance ortofon as standard..om5e i think...and sounded very good indeed. I will say this...the arm and cartridge could track the kind of warps on a record that would throw most arm & cartridge combinations into orbit..and it mattered not how level the turntable was either...you could tilt the turntable some 15 degrees forward or sideways and it never flinched!...
    i think the spring based tracking force has some merit..however this arm did have rather flimsy bearings that developed play within a year..and heavy cartridges were difficult to balance out due to its low mass design..you had to back the counterweight off util it almost decoupled from the arm stub...
    so i guess the answer is.. if done correctly perhaps it can be more forgiving on high complaince cartridges...
    i suppose having a constant force acting on the arm that doesn't rely on gravity alone at least ensures the effects of warps are minimised in terms of downforce...but to a certain extent the mass of the arm itself will still have some influence with how heavy a cartridge you can use ..and perhaps to some extent..if there is any kind of damping in the downforce spring itself..
    i'm guessing using 2 springs (the cantilever's suspension plus dynamic downforce) has its own complications ? :dunno:
     
  18. JohnVF

    JohnVF Lunatic Member

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    This needs to be saved somewhere. Its the most concise description of this I think I've come across.
     
  19. aabottom

    aabottom Swing

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    Hey I liked this explaination and analogies too. Good job melofelo and dlaloum! The car and spring analogies really make it clear.

     
  20. bhundu

    bhundu Addicted Member

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    Ok. I'm starting to understand. I can see how RFs can cause issues.

    I thought TF applied by weight was uncontrollable due to Gravity and that springs slightyly got around that? A tighter spring acts more force doesn't it?

    Edit: ie the vertical modulation would have a varying force?
     
    Last edited: Jul 18, 2011

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