Compliance of Cartridge and Tonearm

Here's another article that explains what we are shooting for;

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

WHile I do not know the specifics as I do not have any Koetsus I imagine that there might be some differences in mass in the cartridge line that could account for it. Aren't there stone and wood versions of the same generator body?

Beau

bonzo75 said:

This was an article written by Pepe57, whom I visited in Milan over the weekend, detailing how to match the weight of the arm and cart so that it resonates between 9 to 11Hz. Not sure how many of you abide by the math and how many of you don't.

http://remusic.it/EN/The-Compliance...-of-the-TonearmCartridge-Combination-05728c00

To summarize, if your arm weighs 35g (FR 66, Ikeda, Kuzma are all heavy arms, I think), and you have say, a total of 50g, then if the compliance of the Koetsu at 10Hz is 12, so 12*50 = 600, square root of which is 24.5, and using 24.5 to divide 159, and then deducting 10%, you get approx. 5 - 6Hz.

Which is too low, as it should be between 9 and 11. But by this logic, you need a lighter arm for the Koetsu, while the users here have reported being happy with heavier arms.

What are experiences in practice vs the actual math?

Click to expand...

Is this the formula you summarize?

where:
frez - resonant frequency of tonearm
mef - effective mass of tonearm
mc - weight of cartridge
ms - mass of the screws, nuts, spacers, washers, shims
c - compliance of the cartridge.


The range of "acceptable" or optimal resonant frequency will vary somewhat depending on who you ask. Here was cited 9-11Hz, several say 8-12Hz, FKuzma says 6-16Hz.

The Vinyl Engine addresses the issue providing calculators to make the job quicker. Instead of 'arm weight, these, like the above formula, ask for tonearm effective mass.

The Cartridge Resonance Evaluator asks simply for Tonearm Effective Mass and emits a chart covering a range of cartridge+mounting hardware total mass vs cartridge dynamic compliance. Colored results indicate the relative 'safety' of a resonance frequency based on those parameters.

The Resonance Calculator works with more parameters to give a more exact Resonant Frequency.

One factor of these calculations is assessing cartridge compliance. Different manufacturers give compliance specs measured at different frequencies and it is not always obvious which they use. The above calculators are based on compliance stated at 10Hz. Many (but not all?) compliance figures of European manufacturers are measured at 10Hz. Many (but not all?) compliance figures of Japanese manufacturers are measured at 100Hz (for example, Lyra.) Suggestions for conversion of Japanese compliance to that measured at 10Hz has the Japanese result multiplied by some number in a range of 1.5 to 2. Given that variability, the suggestion is to use x1.75. Hopefully an expert in these things will correct any errors here.

The Koetsu Urushi Gold has its compliance of 5 measured at 100Hz. x1.75 give 8.75 cu. Cart mass of 10g, suppose mounting hardware=1g for total of 11g. Mounted on a Kuzma 4Point (14g effective mass,) the resonant frequency comes in ~11Hz, inside the "safe zone"

... just read the article by Massimo Riserbo, link in first post - excellent - thanks for that!

The effective mass of the Ikeda 407CR1 is about 32 grams. Add 12 grams to that for the Koetsu Onyx and you're at 44 grams. The compliance is 5. Going by this calculator: http://www.resfreq.com/resonancecalculator.html we see a res-FREQ about 10.7hz. Pretty good on paper. Sounds good too.

Hi,

bonzo75 said:

This was an article written by Pepe57, whom I visited in Milan over the weekend, detailing how to match the weight of the arm and cart so that it resonates between 9 to 11Hz. Not sure how many of you abide by the math and how many of you don't.

What are experiences in practice vs the actual math?

Click to expand...

For my cartridge/arm combination the maths obtain a frequency of 7.2 Hz. The Shure's dynamic stabilizer adds another 2 Hz, makes 9.2. All is fine, never had a resonance problem.

One point that should be mentioned in this context: there is no such thing as THE effective mass of a tone arm since this mass depends on where the counterweight is located with respect to the arm's pivot and this in turn depends on the weight of the cartridge and the tracking force. I asked a couple of arm manufacturers, so far the only answer was from Kuzma, he uses a 10 gr cartridge and 2 gr tracking force for determining effective mass of his arms.

Klaus

If you change the mass of the counter weight thus increasing the mass of the tonearm in the denominator of the above equation, it would appear to have an effect of the resonance frequency. Is there a limit or range within which you can expect a heavy weight on a light arm(ex my 10inch 3D with Koetsu RSP 180g weight) to improve the sound, or is just as simple as changing the counter weight mass with a large/smaller arm? Also any opinions on cart arm combos, I have a classic 3 with 10 inch 3d and JMW, The aforementioned Koetsu, zyx airy 3, and a Lyra Kleos sl. If the resonance frequency is too low, what are the audible impacts? Thanks so much.

kleinbje said:

Also any opinions on cart arm combos, I have a classic 3 with 10 inch 3d and JMW, The aforementioned Koetsu, zyx airy 3, and a Lyra Kleos sl. If the resonance frequency is too low, what are the audible impacts? Thanks so much.

Click to expand...

Nice gear. Perhaps the following can shed some light, at least from my perspective. This subsonic energy can be quite substantial, therefore some rooms/speakers/systems perform better when filtering is applied, so it won't tax equipment down-stream.

Even after proper calculation, once mounted, subsonic characteristics include the LP, these always variable. Some examples ...

2 rips, both 45 rpm but different LPs/tracks, (uber-expensive tt/rig). Notice the very different characteristics, although clearly the common peak is ~6hz.




The following 2 (my rips), using the same 33rpm LP, same instance, even the side ...



Again, same peak, but very different overall characteristics.

1 more, just for sh!ts & giggles, a commercial CD, known for its wide dynamic range ...

kleinbje said:

If you change the mass of the counter weight thus increasing the mass of the tonearm in the denominator of the above equation, it would appear to have an effect of the resonance frequency.

Click to expand...

If you use a heavier counterweight for the same cartridge and tracking force, it will be closer to the pivot and will thus decrease the arm’s effective mass and increase the resonance frequency.

Is there a limit or range within which you can expect a heavy weight on a light arm (ex my 10inch 3D with Koetsu RSP 180g weight) to improve the sound, or is just as simple as changing the counter weight mass with a large/smaller arm?

Click to expand...

I do not consider the counterweight as a sound tuning measure, simply because there is no evidence to that effect in form of controlled listening tests. If there is a problem with resonance frequency of a particular cartridge/arm combination and a heavier (or lighter) counterweight can fix that problem, then do it.

If the resonance frequency is too low, what are the audible impacts? Thanks so much.

Click to expand...

When the system is excited to resonance wow can be generated and in severe cases the needle might loose wall contact. Another phenomenon can be observed which is a scrubbing motion in the direction of the groove. This motion will also generate wow which might be audible:

Anderson, “A vibration stabilizer system for phonograph reproduction”, Audio Engineering Society preprint 1356 (1978)


Klaus

Edit: J. Gordon Holt on cartridges:

Pickups
The first component or link is known as the pickup, because it picks up the bends in a record groove and converts them into various forms of distortion and frequency response. The turntable is sometimes considered as integral part of the pickup, but it isn’t really because they may be purchased separately as well as together. Pickup arms may be purchased separately too, except when the turntable is a record changer.