[BaMorin]

The physicists of the VinylEngine community went into this in awfully mathematically geeky depth on the tonearm mass thread out there....


David

  ......... ......

Um.......OK

[dlaloum]

I never said it wasn't a good thread mind 

And my other half looks over my shoulder sometimes as I post on these forums..... her comment - "I cannot believe that there are entire communities of people like you out there..." ...

bye for now

David

[TheChairGuy]

I especially like the bit where we are "Boring"....

bye for now

David

Ha - maybe bearing would've been a better word for it...boring wasn't used purposely; ie, as is in something that is boring.

Yeah, this little circle is now the 6th busiest at AC and while it was the beneficiary of something of a vinyl revival going in the past 5 years, I have always tried to tilt it to seasoned vets and newbies alike to cultivate more interest here.

Seasoned folks, already having heard the 'best' of digital technologies and have been mostly underwhelmed by it, get passionate about vinyl.  With increasing time comes increasing knowledge and curiosity how to unlock more from the medium. From that comes very high minded conceptual conversations between well informed, experience vinylphools...which is GREAT.

But, if your a newbie looking it, you get that there is something exciting going on...but, the concepts are beyond your ability to grasp right now (or ever, if you just want to play music on your record player without hassle of excessive tinkering). I just don't want to lose any newbies along the way without proper balance of beginner and advanced topics here.

Anyhow, back to the topic at hand, a good one to learn from, but not imperative that you 100% understand it to enjoy vinyl 

John

[neobop]

Boring down on these details is ___. Dare I say it?

That not said, I think Silos was bought out by American Appliance.

Maybe newbies are better served by examples of cart/arm combos - what works and what doesn't, and a general guideline. Then specific combinations could be considered on an individual basis.

Hotrod,
The DL-S1 and 304 are unusual carts when it comes to cu, arm mass and VTF. In this case I don't think cu gives any real world indication of 10Hz cu.
Compliance/arm mass estimators are just that, estimators. There are plenty of examples where they're wrong. What's the tolerance on the cu spec from a manufacturer? How can we be so exact with an estimator?
neo

[orthobiz]

I took Physics for Life Sciences in college and Calculus damn near kept me out of med school. If I have a question, I'm posting it here!

Paul

[orthobiz]

OK. Weigh the arm at the cartridge end? Does that mean measure the downward force with the counterweight off when everything is set to zero? Put a scale under the headshell?

Picture?

I just know I'm gonna get it...

Paul

[dlaloum]

Measuring tonearm mass - the easy instructions:

Preperation:
1) have an accurate (preferably digital) stylus scale that can read from say .5g to 15g
2) Larger scale (digital kitchen scales?) to weigh the Counterweight (70 to 250g)
3) Download the calculator spreadsheet I linked earlier (EMC - effective mass calculator - all the physics is built into the spreadsheet)

Measurements:
1) Measure (or read from TT/Arm specifications) the tonearm length from pivot point to stylus
2) Weigh the counterweight (removed from arm) on the kitchen scales
3) Weigh the headshell (if removable) on its own (wires are ok)- if removable
4) Weigh the cartridge/stylus and fittings
5) Weigh the bare arm (cartridge and headshell and Counterweight removed) - at the tip of the arm (where the headshell goes) roughly at record playing angle. (I put my scale on the platter, and let the bare arm lean on it...)
5) Plug the values into the EMC spreadsheet
6) Plug the value for the desired VTF into the spreadsheet (yes VTF affects total mass for an arm where the CW position is used to apply VTF... for dynamically applied VTF arms this does not apply - eg: JVC/Denon/Sony Servo arms - for those arms set VTF to 0)

Read the result.... go use it in your compliance / resonant frequency calculator
eg:http://www.resfreq.com/resonancecalculator.html


This process should be highly accurate for a straight arm - and slightly less accurate for an S or J Arm.

For best results in playing records - aim for a resonant frequency of between 9Hz and 11Hz

Below 6Hz and above 14Hz are problematic - the low end due to becoming very sensitive to footfall, or other natural household vibrations (may not be an issue for you if you have a very stable platform...) the higher end will start to affect bass performance noticeably.

For a cross check of the results in real life - mount your cartridge up, and using a test record with a low frequency sweep test tone sequence (eg: HFN test record) - watch the needle carefully and find the frequency at which the cartridge gets the "wobbles". - The "wobble" point is the resonant frequency.

Now for the Geek stuff....:

Given the measured frequency and your previously calculated Effective Arm Mass - you can now use the resonance calculator to work out what the real compliance of your cartridge is....
Or (if you trust and have access to manufacturer compliance specs) you can use the real resonant freq combined with the manufacturer compliance spec to calculate an estimate of the Effective Arm Mass....

Due to the level of accuracy available for the resonant frequency measurement being.... broad... this measurement is really a rough rule of thumb... best used as a cross check

The tonearm mass calculator is quite accurate....

For a more accurate determination of the resonant frequency - you need to record a known good frequency sweep test, run it through a Real Time Analyzer / FFT to get a frequency response plot from it, and identify the resonant peak. - This is easy IF you have the tools... and will provide a very accurate reading of the resonant frequency.

bye for now

David

[*Scotty*]

Paul,the short version in a word, yes. This is more less an exercise in high school physics . If you think of this as just a teeter totter with a spring on one end. The compliance of the spring is known and the mass of the lever arm of the teeter totter is the unknown.
 There is a substantial flaw in the approach outlined above however.
   Because we cannot separate the lever or arm from the bearing assembly we can only approximate the mass of the arm. The problem that generates the inaccurate measurement can best be understood by taking a 1 ft. long ruler and weighing it by placing it on the scale. You now have the true mass of the ruler.
  Next,take the ruler and support it close to one end and then place the other end on the scale and observe that your measurement of the mass of the ruler will now vary depending on whether the ruler is level with surface of the scale or whether the support point is above or below the surface of the scale. The support point is analogous to the bearing pivot point.
  Depending on the support point location and it location on the ruler and its position above or below the scale surface you can generate a mass value for the ruler that is much less than half its true value.
 I think the overall impact of the error on the low side for tonearm mass will generate a value for the arm/cartridge resonant frequency towards the high side and in some cases close to the audio band. In reality the the arm/cartridge combination
may be just fine. Plugging bogus tonearm numbers into the formula is going to result in bogus results that probably won't make much sense sometimes.
Scotty

[dlaloum]

Scotty,

 before making assumptions, might I suggest that you should take a look at the formulae and physics involved in the spreadsheet itself?
Or read the VinylEngine thread that led to its creation some months back...

If all this was about was weighing the tonearm, we wouldn't be talking about physics and maths - and there would be no need to use a tool such as this spreadsheet...

Instead we have to take into account lever effect, moment of inertia, pivot point and distance of masses from the pivot point etc...

My own version of that spreadsheet (which was far less elegant... and results were much the same) used some of the following:

Mass of Cartridge side of arm (Z) Z=W*2
Moment of Inertia (Ic =  m * r * r) - counterweight side
Momen of Inertia - headshell side Ih=Z*(L*L)/3
Effective Mass (M)  M= (Ic+Ih)/(L*L)

CW=m
Center of mass of CW to Pivto point distance = r
Tonearm weight with headshell & no CW at horizontal = W
Effective tonearm length - stylus to pivot = L

The other thing to keep in mind, is that mathematical rigour is pointless once you have reached a certain level of accuracy.

There are a bunch of factors that affect the end result... precise position of the mass will affect the tonearm - so the amount of headshell mass that is in front of as opposed to behind the cartridge would have an impact - but the impact would be too small to be relevant....

In any case I would be very happy to hear of a simpler tool that provides a similar level of accuracy. At this stage, the spreadsheet mentioned and the process mentioned seems to match manufacturer specs on arms where it has been tested - and appears to coincide with expected/measured resonant frequencies... (which is a good sign!)

If you find a specific flaw in the calculations or results - why not raise the issue, and see whether we can't develop a better tool?


bye for now

David

P.S. I hasten to add that I did not develop the Spreadsheet - LuckyDog did. but having worked through copious reams of postings on leverl / mass / inertia physics/maths, and developed a couple of my own calculators based on all that, I was very happy to get hold of LD's work - test it against my own... find that the results were very close, and decided to stop worrying about it and use his tool...

[*Scotty*]

David,I performed my experiments with the ruler and my digital scale just as I described in my post.
My misunderstanding of the factors involved appears to revolve around the total mass vs. the effective mass. If the numbers generated are in close agreement with the factory specs then all is well and it is my bad.
Scotty

[dlaloum]

Hi Scotty,

yes the terms are ... problematic.... and I am neither an engineer nor physicist (quit those subjects at Uni to focus on computing...).

Like many things in our hobby the commonly used terms may or may not reflect the terminology commonly used in science/engineering.
This is intentionally done to ensure geeks like us are entertained in endless postings that ultimately come down to differences in definitions of terms....

The tonearms are actually quite a complex system - and ultimately what is important to us is how to measure the value required for the calculations of resonant frequency...

The three interdependent parameters being 1) "Effective" Tonearm Mass (not sure what the scientifically correct term would be...) 2) Cartridge compliance in Cu measured at 10Hz 3) Resonant Frequency in Hz

With any 2 of these one can work out the third.

The easiest to get a reasonably accurate estimate of is the Tonearm... (due to the fact that most of us already have stylus tracking force gauges.... and kitchen scales)
There are threads elsewhere discussion the actual "strict" methods of calculating real effective tonearm mass.... but these seem headed towards requiring resources and equipment that very very few of us actually own!

One nice thing about the ECM spreadsheet - is that you can see the effect on mass of varying the CW mass....

This means it is possible to model what happens when you use a lighter headshell, and combine it with a lighter CW.

Working with this model, you can also see that a heavier CW closer to the Pivot point has lower effective mass than a lighter CW further away. (both of which will balance the arm)
And that achieving the lowest possible effective mass (one of my goals for my high compliance cartridges) may in fact involve using a heavier CW.

Based on some of these calculations, I have collected a series of differing CW's that fit my arm (89g, 96g, 110g) the difference is not huge in terms of effective mass, but is noticeable when combined with a lightweight headshell and Nylon screws. (I may be able to move it from 20g down to 14/15g).

This will in turn move some of the resonant frequencies a touch upwards (or downwards for some of the low compliance cartridge where I need to add mass.... also a possibility) for better matching.

I have not yet gotten around to trying all this out and confirming (or not) the audible benefits.
But I can now use some of my lightweight headshell/cartridge combo's which previously would not even balance on the arm!

bye for now

David

[orthobiz]

Luckily I just put an akito 2B on my Linn LP12. Now I have a Linn table with a Linn arm and a Linn (Adikt) cartridge. I would hope I'm in "compliance."

The explanations above do make the whole topic more understandable. Thanks.

Paul

[*Scotty*]

David,just a thought here, but the mass in the counterweight is always roughly equal to the mass of the long part of the tonearm. If one were to set the mass of tonearm to double the mass of the counterweight plus the mass of cartridge and headshell,I suspect that you would have very close to the actual effective mass of the tonearm/cartridge combo and you be a little on the low side because the mass of the stub the counterweight travels on could not be accounted for.
 Could you list the cartridges you are using as I was wondering the range of compliances were that you were trying to optimize the arm to.
Scotty

[dlaloum]

According to the tonearm database (another good resource!) - http://www.vinylengine.com/tonearm_database.php?make=Linn&sort=1&ascdesc=ASC&search=search&mdl=&eflo=&efhi=&mdlo=&mdhi=&ohlo=&ohhi=&amlo=&amhi=&cw=&mp=

The Akito mkI has a mass of 10g (no mass was quoted for the mkII)

According to http://www.musiikin.com/vinylspecs.htm


The Adikt has
mass = 8g
Compliance = 10cu

So total effective system mass of 18.5g (allowing 0.5g for screws)
Cu = 10

Resonant frequency should be around:11.9Hz

If anything a touch on the high side...

it might respond well to a touch of additional weight

If the results of the "googlings" was correct - for a compliance of 10cu - optimum mass is around 24g.

Linn recommend them as a combo... so they will almost certainly be fine together.

That is not to say that you cannot tweak to improve things! 

After all LP12's have a legendary collection of tweaks!!

But before messing, you should use a test record to see where  the resonant frequency is roughly located... if you find it above 11Hz - then you can tweak by adding a bit of weight to the arm.... (or at least you will then have a "mass budget" to use on tweaks!)

Various forms of damping can improve performance - but they all add mass... a major issue in high compliance cartridge world.
But if you have a low compliance cartridge (like the Adikt) - then you have more latitude for tweaking.

eg: some people put a dab of plasticine on the arm (plasticine tends to absorb frequencies between 300 and 3000Hz) - or a herbies tonearm damper (clips onto the arm tube)
Some people wrap the arm in tape (another form of damping)

There are also dampers in the form of shims made of different materials... that can fit between cartridge and arm.
And then there are shims that are straight weights...

So if bitten by the tweak bug - you have lots of scope!

Enjoy

David

[dlaloum]

David,just a thought here, but the mass in the counterweight is always roughly equal to the mass of the long part of the tonearm. If one were to set the mass of tonearm to double the mass of the counterweight plus the mass of cartridge and headshell,I suspect that you would have very close to the actual effective mass of the tonearm/cartridge combo and you be a little on the low side because the mass of the stub the counterweight travels on could not be accounted for.
 Could you list the cartridges you are using as I was wondering the range of compliances were that you were trying to optimize the arm to.
Scotty

Hmm the counterweight issue is not so simple as the impact of its mass is related to the square of the distance.... which is why moving it back has a huge impact on effective mass, and also why a heavier CW closer in counterintuitively results in a lower effective mass.

Conside that the counterweight for a Technics SL1200 weighs around 100g - the manufacturer spec for the arm is 12g effective mass!

Measuring my own arm - the weight without CW fitted, with headshell removed measure with the scale on the platter and the arm level = 9.2g
The original manufacturer CW = 110g
Headshells that I have in my stash range from 5.5g to 13g
Headshell wires tend to be around 0.4g
Metal screws tend to be around 0.4g
Nylon screws tend to be around 0.15g

Cartridges in my repertoire

Audio Technica
AT150 (using 440MLa stylus)
AT440MLa
Signet TK4/6 (using 440MLa stylus)
SLT96 (using 440MLa stylus)
AT12Sa
AT20 (waiting on a stylus)
Signet TK7su (waiting on a stylus)

Shure
1000e (M97xE-SAS stylus)
MT105p (M97xE-SAS stylus)
M75p (M97xE-SAS stylus)

Ortofon
OMP20
OM20
Digitrack 300SE
OM with 300SE stylus
320U
MC200 (NIB unopened.... soon...)
VMS30 mkII

Empire
MC1HO (Benz Micro)
EXL10 (waiting on stylus)
2000e (waiting on stylus)
999 (Waiting on stylus)
875XT/Azden YMP20E(waiting on stylus)
1085LT (waiting on stylus)
LTD400 (waiting on stylus)

Sony
XL-MC104P

ADC
SuperXLM
XLM Digital Series II
Integra Digital Series II

Panasonic / Technics
EPC-P33 (waiting on stylus)
EPC-451 (strain Gauge)

Grado
Gold1

I've embarked on a vinyl project - decided that the only way to tell what these sounded like was to listen to them....
Many of these I got for a song stylusless - but some of them are classic cartridge, and I am looking forward to working my way through these....
I also have many! other bodies of lesser interest.

The key point is that with one or two notable exceptions (MC / Straingauge) they are mostly high compliance - and in some cases (ADC SuperXLM) very high compliance....

I have two turntables:
1) Revox B795 linear tracker - Arm effective mass 4g (!!) - with cartridge around 12g
2) JVC QL-Y5F - japanese DD with servo damped arm effective mass 16g to 24g depending on configuration (using various CW / Headshell / cartridge combinations)

The JVC is interesting as I can dial in as much or as little damping as desired - mind you the damping is focused on the lower frequencies.... so if I want to tweak for mid/hf damping I will need to us other methods.

Clearly proper use of damping can allow a wide range of compliances to be used on a single arm  - but will it sound as good as a proper "matched" set?

Exploring all these interesting topics...

bye for now

David

[*Scotty*]

That is a fascinating collection of cartridges. I am definitely at the other end of the spectrum. I have been using the same cartridge,an AT 440ML since 1996. The inductance of the cartridge is canceled out by connecting a second AT 440ML cartridge body to ground.  That is the point where I stopped. I
do wonder if I could run an AT 150 stylus in the 440 ML body.
Scotty

[dlaloum]

Absolutely yes....

If you are shopping for the next stylus step up you could got for some older NOS styli: 155LC, 152LP/MLP, if you can find them even the older 180/170/160..... and the current 150MLx

I decided to go for a 440MLa and try it on all the various cartridges I have that can take that family.... then I can decide what I like best and whether the cough up for a boron/beryllium cantilever...

I have to say I am disappointed by my AT440MLa - primarily due to channel imbalance (resistance L/R = 758/787) which leads to not only a level imbalance but a frequency response imbalance... my example of it may be a poor example...

I've also been experimenting with using a "cancelling cartridge".... not convinced yet... still experimenting with that concept.

but we are meandering off topic

bye for now

David

[DaveyW]

I've followed ths thread with much interest and first up would like to thank all of the contributors so far (especially Dlaloum for taking the time out to draft such detailed responses).
It's always easy to forget that all who contribute here do so in their own, generally very valuable, free time 

My concern in all of this though, is how much of an audible effect Resonant Frequency matching really has and if we convince ourselves that 10Hz is the magic number, how much we  might restrict cartridge choice because of this.

I've read many posts where 10Hz is sought as some form of Holy Grail - I think we do need to put this in some form of balance.

I've run a reasonable selection of carts on my Ittok and using the VE Tonearm and Cartridge databases, they've worked out at between 7Hz (Stanton 881s II) and 13Hz (Denon DL110)

Personally I don't believe I had any audible issues with either of these carts while playing music (as opposed to test discs).
Both performed admirably at their respective price points, and I did'nt feel it necessary to apply any form of resistive loading mods to adjust their tonal characters.

Maybe I've just been lucky and/or the Ittok is a little less sensitive to this sort of thing, but from my perspective I'm very much in the camp of just try it and see and don't put too much sway into resonant frequency matching.

I'm sure I'll get blasted into the weeds on this from certain quarters, but these are my experiences.

Saying all of this  - my current cart of choice sits at around 9.5Hz, so maybe............ 

One things for sure - you can't do this only by numbers.

Cheers
Dave

[neobop]

I'm in complete agreement with you Davey. The object of this is to optimize sound quality. Arm/cart matching as it relates to compliance might have implications for the sound, which is rarely talked about. It's like your combo is in a beauty pageant and you're seeking a perfect 10. There's nothing perfect about it.

Of course there are implications and you won't have good results putting a Koetsu on a Black Widow, or an XLM on a FR64S. It's been my experience that med/high cu carts tend to sound sluggish on an arm that's too heavy. On the other hand, I suspect the 881, resonating at 7Hz with a 13g arm, sounds better than some other carts with a more "desirable" resonant frequency.

Woofer pumping or problems with footfalls is usually caused by improper physical set-up of the table not inappropriate resonant frequency. Acoustic feedback or susceptibility to physical movement is the #1 cause.
I'm not saying this should be ignored. What I'm saying is sonic consequences are the top priority IMO and cu/arm mass is only a part of that.
neo

[orthobiz]

Special thanks to David and Scotty for addressing my posts personally. And thanks to everyone else contributing. It's making a subject that had me bamboozled a bit more clear!

Paul