Actual cartridge compliance specs - what do they mean?

Lapslah

Super Member
People often talk about cartridge compliance in terms of high, medium, or low. But when I look at a spec sheet, it doesn't list the cart in those terms, but rather by actual numerical values, like the following from my AT-OC9-iii:

Static Compliance - 35 × 10 - 6 cm/dyne
Dynamic Compliance - 18 × 10 - 6 cm/dyne (100 Hz)

Without many samples of other specifications, there's no way to know where this fits in the high, medium, low spectrum. Can anyone provide a range for each general category to make this easier to understand?
 
"compliance" just means by how much a spring complies under load. The stylus assembly on the cantilever and suspension is regarded as a spring and the load is the mass of the cartridge + the VTF. The units are basically distance per force in 1 millionth (10 in the power of -6) of a centimeter per dyne. It can also be expressed as meters per newtons but we don't really care. We just call it "cu" for compliance units. It's kind of like a currency where 20 cents is always less than 30 cents so 20cu is always stiffer (less compliant) than 30cu. The difference is we have two different currencies with a funky and volatile exchange rate. More about that in a bit...

Static compliance is like measuring the compression of a spring with some load (weight) applied to it. More weight, more compression - it's a linear straight forward relationship. Not many manufacturer's exclusively settle for the static compliance of their carts. Shure is a notable exception. I don't know why they only state static compliance but it's a source for confusion and misconception regarding their carts compliance. It's not a common practice and definitely not very informative. It is, however, static - hence frequency independent.

Dynamic compliance is a little more complex b/c if you take the spring and oscillate it 10 or 100 times per second, (cycles per second, or simply "Hertz" or "Hz" units), and try to measure the distance it compresses with the same load as before, it would be very different. Not only that, it would also vary between the 10Hz and the 100Hz.

With the analogy of the cantilever and a loaded spring, the frequency at which dynamic compliance is measured becomes important. The cantilever actually oscillates all the time as a reaction to the stylus reading the groove modulations. Static compliance isn't exactly the best indicator of performance in this case. Most manufacturers specify dynamic compliance and sometimes provide the static compliance too - but they do not all use the same frequency in dynamic compliance measurements!

Here's where we use two different "currencies". The Japanese traditionally measure dynamic compliance at 100Hz, while the rest of the world uses 10Hz. Everyone calls it "cu", just like many currencies use "cents" to denote the 1/100th part of the whole. For dynamic compliance the frequency is critical - just like knowing the currency of a price denoted in cents. Is it Euro cents or USD cents? It matters - a lot!

Unfortunately, there's no good equivalent of a currency exchange rate between cu@100Hz and cu@10Hz. A Denon DL-103 dynamic cart compliance is specified as 5 × 10 - 6 cm/dyne (100 Hz) and conforms to the Japanese standard of denoting it. To convert it to 'our currency' of cu@10Hz, we generally use a multiplier of anything between 1.5 and 2.2 and we try to factor in the mfgr recommended VTF, under the assumption that higher VTF goes hand in hand with the less compliant carts. I like to use 2.0 so the Denon 103 compliance at 10Hz is 5 X 2.0 = 10. It's arbitrary, inaccurate and unfortunately doesn't work very well in all cases. Some Nagaoka carts turn out to be way more compliant than this method indicates.

Finally - the point of knowing the cart's compliance in cu@10Hz terms becomes important in regards to calculating the resonant frequency (RF). RF is the frequency that may induce the cantilever to oscillate in an ever cascading uncontrollable manner. It's bad thing for us but it's a physical thing that will happen to a loaded spring and we can't avoid it. We can, however, try to restrict the spectrum of frequencies at which this happens to a known 'harmless' range.

Our ability to control the RF depends on the relationship of the cantilever compliance and the effective mass of the tonearm. Effective mass is not in any way the weight of the tonearm - or it's mass. It's a layman's term which describes the tonearm's total moment of inertia and it roughly equates to a car's road handling as a function of it's mass distribution over it's dimensions and it's suspension system.

In a nutshell - the tonearm's inertia is a force that opposes the stylus desire to change direction as a reaction to the groove's modulations. We want to keep this conflict at minimum for as much as possible. The general rule to approach the equilibrium in this domain is low compliance ('stiff') carts are compatible with high effective mass tonearms (hefty) and high compliance carts ('springy') match low effective mass tonearms (light). We need the cu@10Hz b/c most cart/tonearm matching formulas rely on the compliance at 10Hz. See more about cart/tonearm compatibility here.

I hope this makes sense. I've tried to be brief but it's a rather encompassing subject so I guess that's as short as I could make it.

TL;DR I know I did not give you the range split in cu for low, medium and high compliance, but that's just because it's as volatile, arbitrary and varies as much as who you ask.

Be your own judge.
 
Last edited:
Forget multipliers, they don't work with Japanese specs and will give off results in many cases. Best bet is to look for a bench test or a user that measured the resonance on a tonearm of known effective mass.
 
Check my database https://docs.google.com/spreadsheets/d/1CPSW9PMLb3rkIdZQHpvnpVmcxXVF7Bal2Uz7YkKYR28/edit?usp=sharing , which has real-world measurements of low frequency resonances for more than 700 arm/cartridge combinations, from magazine reviews (American, Australian, British, German and occasional Dutch or Swedish) of the last 50 years.

It can be sorted (tabs at the bottom of the page) either by cartridge or turntable/tonearm, and I’m still updating the list – I just put another 25 in today.

An OK arm/cartridge match is one with a resonance between 8 and 12Hz.
 
Last edited:
Thank you all for the well written responses. I had a pretty good handle on all of this already and was just looking for a way to categorize the numbers, but I'll admit I picked up a little bit of new knowledge.

If I'm reading right, my dynamic compliance listed in the OP, being 18 × 10 - 6 cm/dyne (100 Hz), when you factor in the (admittedly inaccurate) multiplier of somewhere around 2, would have a cu in the 30's, making it pretty darn high compliance, yes?

The motivation behind all of this is that I have a cart I like and would like to upgrade my arm to make the most of it. My current arm tracks fine and sounds good, but I don't believe its effective mass is low enough to make a good match with my cart - on paper. I'm thinking of upgrading because I'm under the impression that matching the arm and cart can have sonic benefits beyond curing feedback and tracking issues. In other words - despite not having any negative issues with my current setup, can I expect better sound with an arm more suited to my cart? I'd hate to spend significant money on a new arm and not hear a difference, which is why I'm looking to science to save me from going down the wrong path.
 
Check my database.

Thanks, ETI. Your database shows my AT-OC9-iii matched with an arm with an effective mass of 8g, with a resonant frequency of 9Hz, which should work fairly well. Question - how does the resonant peak figure in?
 
Question - how does the resonant peak figure in?

The peak should be as low as possible (well-damped). The average of all those with levels in the database (more than 300) was around 9dB, and anything above about 15dB is getting towards being too high in level, and may cause problems, with excessive IM distortion and unsecure tracking.

Anything under 10dB should be OK, and 5dB or less is excellent, and will result in very secure trackability of warps or eccentric discs, as well as much-reduced IM distortion, where the (unwanted) resonance modulates recorded music frequencies to produce unwanted (distortion) signals. It's also possible for the resonance to interact with other unwanted frequencies, including rumble (either from the turntable, or recorded) and acoustic feedback, so a very small resonant peak is desirable for the best sound.
 
Last edited:
AH - I missed the "dB" in the header and thought the resonant peak figure was in Hz, which is why I couldn't figure it out.
 
AH - I missed the "dB" in the header and thought the resonant peak figure was in Hz, which is why I couldn't figure it out.

It is Hz. I try to have the tonearm/cartridge low-end natural resonance around 8-10Hz. This range gives best bass, without undo rumble and acoustic feedback. In my experience. :)
 
Shure M97HE-AH & Technics SL-1200MkII Resonance.jpg

Graph of the resonance of a Shure M97HE-AH cartridge in a Technics SL-1200 MkII tonearm. Note that the zero dB level is at 30dB on the graph 'y' scale.

Left peak (stabiliser not operating to damp the resonance) = 11dB @ 6.5Hz (to the nearest 0.5Hz) - too low to be a good match
Right peak (stabiliser brush operating to damp the resonance) = 6dB @ 8.5Hz (approximately) - acceptable match with tonearm

So the stabiliser brush has acted to increase the resonant frequency to acceptable (by adding extra stiffness), as well as almost halving the level from 11dB to 6dB. The cartridge tracking will be much more secure with the stabiliser in use, particularly over warps, and distortion will be lower, for better sound, because the smaller resonance doesn't modulate recorded frequencies as much as the larger 11dB one would.
 
Thank you all for the well written responses. I had a pretty good handle on all of this already and was just looking for a way to categorize the numbers, but I'll admit I picked up a little bit of new knowledge.

If I'm reading right, my dynamic compliance listed in the OP, being 18 × 10 - 6 cm/dyne (100 Hz), when you factor in the (admittedly inaccurate) multiplier of somewhere around 2, would have a cu in the 30's, making it pretty darn high compliance, yes?

The motivation behind all of this is that I have a cart I like and would like to upgrade my arm to make the most of it. My current arm tracks fine and sounds good, but I don't believe its effective mass is low enough to make a good match with my cart - on paper. I'm thinking of upgrading because I'm under the impression that matching the arm and cart can have sonic benefits beyond curing feedback and tracking issues. In other words - despite not having any negative issues with my current setup, can I expect better sound with an arm more suited to my cart? I'd hate to spend significant money on a new arm and not hear a difference, which is why I'm looking to science to save me from going down the wrong path.

I find it hard to believe that an OC-9 is a high-compliance cartridge. An example of high compliance is an Ortofon OM series at 30.
 
I find it hard to believe that an OC-9 is a high-compliance cartridge. An example of high compliance is an Ortofon OM series at 30.

One of the recent OC9X models was tested by Miller Audio Research and found to have a Western dynamic compliance of 23 CU.
 
High for an MC is not really high compliance, though.
For most purposes tracking force is an adequate guide to compliance. When high compliance cartridges were the rage, a usable tracking force of under a gram was the rule of thumb - you might go up to a gram and a half, but that was pushing it, and a couple of companies claimed that their highest compliance cartridges could be used at under a half gram (which should be taken with a grain of salt, though the shortlieved original ADC XLM might have been able to do so). So I would consider cartridges tracking in the 1.5 to 2.5 gram area mid compliance and above 2.5 low compliance.
It appears that a certain realism has emerged about the functionality and even the desirability of very low tracking forces, and a more measured fear of higher forces. Consequently, it seems that the definitions of high, medium, and low compliance have shifted a half gram or so upward in tracking force ranges, and sometimes it isn't clear which standard - the 70s definition, or the current one, is being used.
 
Back
Top Bottom