[neobop]

The question is how to convert 100Hz compliance (used by some Japanese manufacturers) to standard 10Hz compliance.

Compliance is a measure of springiness.  We're talking about dynamic compliance, a standardized measured that results are a single number, a compliance unit symbolized as cu. The higher the number the springier the compliance.

If we look at carts like the AT440 or 150MLX (10cu @ 100Hz) and use a test record to measure resultant resonant frequency with a known arm (eff mass), we can calculate the 10Hz cu.  It seems as if a 100Hz cu of 10 = 18cu @ 10Hz.  The conversion factor looks to be approx. 1.75 x 100Hz cu.

Fly in the ointment -  The AT95 is 6.5cu @ 100Hz, yet 15cu @ 10Hz.  That means the conversion factor is approx. 2.3.  For awhile I thought there was a sliding scale for a conversion factor that diminishes as cu goes up.  That seems to work to a certain extent.

Swarm - what about the OC9III ?  It has 100HZ cu of 18 and tracks at 2g.  Oh my, that doesn't compute.

There are more, but for now I suspect there might be some basic questions about compliance, arm/cart resonance.  If you're a newbie or just unsure about this confusing topic, don't hesitate.  The only stupid question is one unasked.

There is a solution to this problem, but that's for next year, unless some smarty pants chimes in before 12AM.
Happy New Year!!   
neo


 









 

[orthobiz]

I was never good at math.
Happy New Year!

Paul

[neobop]

If we look at some other carts where the spec is at 100Hz, most seem to conform to the sliding conversion scale.

DL103 is 5cu @ 100.  That seems to work.  It's a very low cu cart.

DL110 - 8cu  Seems about right

DL-301 II - 13cu.  This cart is a light tracker - 1.4g.  If we slide the scale a bit further, say a factor of 1.6, then 10Hz cu = 21.  Close enough?

DL-S1 - 14cu.  VTF = 1.3g.  These lighter tracking Denon carts seem a bit different in terms of cu.  In my experience the DL-S1 and 304 seem to like arms a little heavier than indicated by conversion to 10Hz cu.  I got best results with both of these on arms around 14g eff mass.  It's not far off though.

AT7V - 7cu.   VTF = 2g.  This fits.  Just a bit more compliant than the 95.

AT-15/20SS - 9cu.  Close, it seems a hair less compliant to me, but I never measured it.

AT-140LC - 15cu.  If we slide the scale a bit further, say a factor of 1.5, then 10Hz cu is 22.5 - reasonable.

Nagaoka MP100 - 5.5cu.  This is a low cu cart, tracks at max 2.3g.  ?

MP200 - 7.2cu.  VTF max is 2g.  As you go up in price with Nagaoka, the carts get a little more compliant and VTF goes down.  No problem with conversion (I'm aware of) with either of these.

Compliance conversion on a sliding scale might not be perfect, but it seems generally close.
neo

[orthobiz]

Appreciate all of your posts but the tonearm/cartridge compliance stuff is incomprehensible to me. Can you recommend a short primer or slightly longer treatise on the subject? I know it can affect which cartridges work best with certain tonearms, etc., but I've never been able to figure it out. I'd like to learn a bit more…

Paul

[neobop]

Hi Paul,
Lets start with standard 10Hz compliance.  That's the figure on which all estimates are based, but first lets attach this to real world arms and carts.

The arm and cart work as a unit and the unit has a low frequency resonance.  It will vibrate as a unit. There will be a resonant peak at the frequency of this resonance.  The idea is to keep this resonance peak within a certain range.  That's 8 to 12Hz.  That's above the warp region and below the music band.

What determines the resonant frequency is the compliance of the cart expressed in compliance units (cu), the weight of the cart + screws, and the effective mass of the arm.  Check out this calculator on the upper left:
http://www.vinylengine.com/cartridge_database_tools.php

Lets plug in some numbers and see what happens - Say you have a CA Discovery - 8g and 15cu and mounting screws are 1g.  How about an 11g arm.
That works out to 9.18Hz.  Pretty close to 10Hz which is right in the middle of the preferred range.

Lets switch arms to a 14g Graham.   That comes out to 8.56Hz - still within the range, but not as good. Okay, lets keep the 14g arm and switch to a Goldfinger.  That's 16g, 15cu =  7.37Hz, a little low.  See how this works?  As you increase mass the resonance frequency goes lower for a given compliance.  If you increase compliance the frequency goes higher for a given mass.  More considerations tomorrow.
neo

 

[neobop]

Other explanations:
http://www.gcaudio.com/resources/howtos/tonearmcartridge.html

http://www.theanalogdept.com/cartridge___arm_matching.htm

Paul, perhaps you remember this discussion from nearly 3 years ago?
http://www.audiocircle.com/index.php?topic=93143.0

neo

[neobop]

I think those links explain compliance better than I did.  Most vinyl enthusiasts are at least somewhat familiar with arm-cart matching and this is a good place to start when considering a new piece.   

It's been stated that 100Hz cu isn't really compliance, but rather a measure of 100Hz tracking ability.  This sort of makes sense because a test for springiness should be at an appropriate frequency below the audio band, and 10Hz happens to coincide with recommended arm/cart resonance frequency.  100Hz is in the mid-bass.  Why test there?

On the other hand, 100Hz cu is measured as compliance.  A 150MLX is 10 x 10-6 (6th power) cm/dyne @ 100Hz.  I believe tracking ability is maximum velocity tracked at a specified frequency.
neo 

[orthobiz]

Thanks for the links, I'll have to check it out.

That old thread brings me back to the days when certain members were more active in this Circle than they are now, not to mention the untimely passing of JohnChairGuy.

Paul

[dlaloum]

Lurking

P.s. Happy New year

[neobop]

Hi David,
Happy New Year.

I'm hoping you can shed some light on this subject of 100Hz cu and the rationale for calling it tracking ability at 100Hz.  The only thing I can think of, off hand, is the frequency.  Results are expressed as cu and not max velocity. 

Here are some reasons why arm/cart matching using a calculator is an estimate, not an exact calculation:
Individual examples might vary somewhat from manufacturers prototype.
The original spec for cu is based on vertical compliance. This was for record warp considerations.   Some companies (Ortofon) use lateral compliance and it's often a different figure than vertical. 
Horizontal and vertical mass can be different on the same arm.  This is especially true of linear arms, but is also possible on a pivoting arm.
Considering only vertical compliance gives a partial picture of the behavior of an arm/cart unit.  Tracking is three dimensional, maybe four dimensional if you consider time. The record and arm are constantly moving.
neo

[MaxCast]

Lurking too.  I have to give my brain a rest after reading the first page of the older AC thread and the Romy link.

[neobop]

Max,
The old AC thread has some interesting stuff like estimating arm eff mass.  Reading that old thread makes me think of JohnTCG.  We were net buddies over at VE before I was a member here.  Everybody misses him.

Romy will have you thinking sideways.  He relates everything to his preferred MCs and characterizes all high compliance carts as junk.  But more importantly, his hearing is one dimensional and he talks a lot of BS.   If you have too much arm mass for a cart, the sound will be sluggish and dull.  Effective mass is not weight, it's exactly the same as moment of inertia which directly effects transient response - the ability of the cart's moving system to start and stop.  Think of the cart as having to drag the arm across the record, and by the needle at that.  But you need enough mass to provide a stable platform for the cart.  A low cu cart on a light arm also doesn't work good.  Estimating the resonant frequency of the arm/cart is only a tool to help figure out appropriate matching, it's not the final word. 

Just to add a little confusion to this whole thing, it was revealed awhile back, that HFN and Analogue Productions test records were off on some of their frequency tests. 
neo

[woodsyi]

Keep up the good work guys.  I am not the brain who can add to this discussion.  It's been a while since I changed arm/cart combo.  I have fooled around with weighted screws to lower my resonant frequency but that's about it.  Why mess with a good thing, right?  But it's always good to know why the things work the way they do.   

[dlaloum]

Hi Folks,

I haven't really gone into the deep end on this one - there was a thread on VE that went quite a way into the issues (including the physics) around arm mass, damping, and compliance... apparently the 100Hz compliance is key in determining the damping in the cantilever suspension.

So although the 10Hz compliance will tell us the resonant frequency, the 100Hz compliance can be used to work out more effectively whether cartridge and arm will match - as the damping of the suspension may well control an "out of place" resonance just as fluid damping can be used to do the same thing.

LuckyDog developed a spreadsheet (http://www.luckydog.demon.co.uk/images/loafer.xls) which models the interactions between the various parameters and can be used to gain a better understanding of what is happening, as well as to assist in calculating a potential arm / cartridge match.

I need to track down the thread that lead to its development...

LD - the physicist and author of the spreadsheet, got turfed off VE for reasons that remain a mystery to me... not sure where he hangs out now. - The process of turfing him out also involved wiping some (many?) of his postings - so the thread may well be partly incomplete as a result, his remaining postings appear as user "goneawol".

To summarise - the 10Hz compliance figure has a completely different purpose to the 100Hz compliance figure - and the 100Hz figure is closely related to tracking ability, damping and VTF....

If I am being a bit vague it is simply that I have not taken the time to date to get my head around the relationships and mathematics involved (another future project) - but LD's spreadsheet work is easy to use, and rapidly provides answers to key questions....

Hope this helps

bye for now

David

[dlaloum]

Here is another very heavily technical web reference site:
http://www7a.biglobe.ne.jp/~yosh/recspecs.htm

This site is truly invaluable - but only digestible in small bites....

here is an example .... a fascinating tidbit of information:

According to the AES report in 1968 by Toshiba engineers: "Trackability Test by Complex Tones and Biasing Force Effects of Phonograph Pickups": "Some of the so-called "high compliance" cartridges have produced larger I.M.D. under the specified tracking force than those of relatively low compliance. For low modulation level both cartridges have similar characteristics, but for high modulation level the former are much effected by side thrusts. Side thrust less than 0.05g is allowed for I.M.D. less than 10%. From this "high compliance" cartridges operating under small tracking force are not necessary good from the viewpoint of degradation by biasing forces".
In JVC book(1979), Shibata as one of the writers commented as follows: "Cantilever deflection can reach more than a few degrees by side thrusts so that tracking angle error distortion is increased. To avoid such occurrence, the compliance should be kept not excessively high, and linear tracking arm (not swinging but linear shifting) is preferable".

Short summary - High compliance cartridges do better in linear tracking arms, for pivoted arms, mid compliance (and matching mass one presumes) is better.... all due to the additional distortion generated by the cantilever movement when affected by side thrust which twists the needle in the groove - mid compliance is less affected by side thrust - and linear trackers have far less side thrust (no need for anti-skating!).

Went to that website looking for further references to 100Hz Compliance spec... didn't find anything - but still read through a few gems!

bye for now

David

[neobop]

Thanks David, that's a lot to digest.

LD is Luckydog who got the boot?  No further comment.

The problem with reading snippets like those on Yost site - they're out of context with little or no clarification.  Like the statement, "Some of the so-called "high compliance" cartridges have produced larger I.M.D. under the specified tracking force than those of relatively low compliance. For low modulation level both cartridges have similar characteristics, but for high modulation level the former are much effected by side thrusts. Side thrust less than 0.05g is allowed for I.M.D. less than 10%. From this "high compliance" cartridges operating under small tracking force are not necessary good from the viewpoint of degradation by biasing forces".

"Some" doesn't tell us much about which.  What's high cu in 1968?  What kind of cantilevers and tips were evaluated and compared to what?
Anyone who has played with light tracking carts knows they're hairy and more easily subject to extraneous deflection, so why shouldn't "some" be more prone to IMD with heavy modulation?

The contention that 100Hz cu says more about damping and tracking, makes sense because of the frequency.  Thanks again for posting the links.
neo 





 

[dlaloum]

It is a bit off topic on this thread, but there are some discussions about the relative levels of distortion of various types of vinyl compromises....

Some things that people obsess about are an order of magnitude lower in terms of the distortions they introduce than other aspects that most people are not even aware of.

I think it is worthwhile sometimes reviewing the level of distortion introduced by various aspects of the whole TT environment, and doing some triage, so as to focus on those aspects that have the greatest impact... the "tidbit" is a pointer to an area worth looking at...

bye for now

David

[neobop]

Not meant as a criticism, more as an observation.  I wonder how many AES papers are presented these days, on these aspects of record playing?

Taking a quick look at the calculator - resonance is lateral?  Isn't that the frequency for tracking ability test?

I'll have to play around with parameters, it looks interesting to say the least.   I think most of us will need an explanation of all the factors/ratios.  Don't worry about staying on topic, we can always get back to 10 vs 100Hz cu.  All this stuff is interrelated anyway.
neo

 

[Ericus Rex]

LD - the physicist and author of the spreadsheet, got turfed off VE for reasons that remain a mystery to me... not sure where he hangs out now. - The process of turfing him out also involved wiping some (many?) of his postings - so the thread may well be partly incomplete as a result, his remaining postings appear as user "goneawol".

I vaguely remember some fierce Grado bashing from him.  Some the fights turned personal, iirc.

[Grbluen]

Perfect timing Neo, I've recently become interested in the possibility of changing the effective mass of my tonearms with the use of weights. I was participating in a thread on VE where there was a discussion about a SME tonearm. This thread opened my eyes to the fact that certain tonearms lend themselves to adjustment by adding mass near the pivot. There have been scores of users lamenting the JMW tonearms for only being suitable for high compliance cartridges. I'm only now beginning to experiment with the addition of mass at the pivot. I've often played with mass at the headshell, but this could open the doors to a greater variety of carts.
As an aside, the OP in that thread was also booted for reasons that I don't quite understand.