Dave, I was using my Acutex LPM320 (C = 42) in an FR64S, albeit with a lightweight headshell. FR64S has M = 35 with its OEM headshell. My headshell probably knocked 10g off that. But add back 6g for weight of the cartridge plus screws, for a calculated Fr = 4.4 Hz. Sounded fantastic until I pulled too hard on one of the Acutex leads and evidently disconnected the ground wire on one side. (This is the cartridge I asked you if you wanted to fix.) Bass was flawless.
PS. I think you're probably right about what Korf meant.
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@intactaudio , I can't be sure what you mean. What to you is an insanely high mass arm (in effective mass please)? and what is a really high compliance cartridge? It sounds fine to you but, I would like to know what is happening where it does not sound, below 8 Hz. If the tonearm is massive enough some very unhappy things are going to manifest and no cartridge I know of (excluding the Decca) has enough damping to deal with it. Hook your phone stage up to an oscilloscope.
As I said before, I do not use formula or rely on theory. I measure. Unless you measure one has no idea what is going on. "Sounds good" is a hopelessly inaccurate way of describing the situation where the needle hits the groove. T
This is for certain. If you add mass the resonance frequency is going to drop. If you remove mass the resonance frequency is going up. If you can't see or hear the resonance point with a good test record it is because the system is dampening it out. In which case it is not a problem. If you want to increase your resolution hook up an oscilloscope to your phono stage (assuming it goes down that low) and you will probably see it along with some other scary looking stuff. |
I think the difference between #5 and #6 is that #5 refers to a mismatch of a low compliance cart to a low mass arm and #6 refers to the mismatch of a high compliance cart to a high mass arm.
Either way... the big thing that is overlooked by everyone thus far is he drastically altered one of the factors (compliance) in the traditionally used formula and kept the other two constant. His results did not show the expected shift in resonant frequency but did show a decided effect on the damping of the frequency peaks. I believe his compliance calculator goes more to showing the possible magnitude of the unwanted behaviors resultant from a mismatch and I think situation #5 is problematic and #6 may be quite benign.
As you have heard, I use a really high compliance cartridge in an insanely high mass tonearm with no apparent ill results. Even though it breaks just about every matching rule known to man and incites endless lectures on my ignorance, I have found it to be a sublimely musical combo.
Einstein one said... “If the facts don't fit the theory, change the theory". Sadly, in this case I don't see that ever happening. |
In Korf’s #5, too low a compliance for a given effective mass is the same condition as #6, too high an effective mass for a given compliance, etc, yet he posits very different outcomes in #5 vs #6. Same for the converse conditions he describes. |
I find the Korf Audio blog post linked above to be very interesting and am surprised nobody makes note of the fact that he seems to call out the "way everyone does it" as flawed. I have tried to back out the actual compliance from other know parameters and found like korf that something else dominates this equation. Below are his conclusions from post IV http://korfaudio.com/blog70http:// 1 Carlson's formula of a low frequency resonance does not describe the measured low frequency behaviour of the cartridge/tonearm interaction
2 Modern cartridges (meaning all those built in the last 60 years or so) have too much suspension damping and non-linearity for the resonances to dominate
3 The frequency of the observed motion is determined largely by the frequency of the excitation
4 The cartridge/tonearm system acts as a lowpass filter for vibrations picked up by the stylus
5 Too low an effective mass for a given compliance (or too low a compliance for a given effective mass) results in low frequency attenuation and excessive tonearm motion.6Too high an effective mass for a given compliance (or too high a compliance for a given effective mass) results in "ringing"—a small resonant peak—that is largely benign
and barely registers in the measurements Oddly enough he also provides a compliance calculator that gives results that are in direct contrast to his measured experiments. dave |
@yeti42, good for you. Measuring is the only way to go. There is enough variability in cartridges and tonearms that the predicted resonance frequency can be a good deal different than the measured one as you noticed. You are not seeing the vertical resonance because it is being well dampened. 8 Hz is perfect, what I shoot for. You can see the vertical resonance if you use a more sensitive measurement device like an oscilloscope. You can put a seismometer app on your phone and place it on your speaker or subwoofer and you might be able to see it. I have not tried it yet but I will once I get my system set up again. |
I just posted by experience on another thread, but it fits here too
When the second of my B&O RX2 turntables gave it up, after a fair amount of research, I ordered a Mofi Studiodeck because I knew I would need complete adjustability to mount the Soundsmith SMMC1 B&O cartridge on another turntable. In that price range, the Studiodeck seemed to fit the bill. Only after the turntable shipped did I learn about potential compliance issues, and that the total 1.5 grams of my Soundsmith high compliance cartridge and adapter were an impending catastrophic mismatch for the heavy arm on the Mofi Studiodeck. Certainly just waiting to happen in some horrible sonic way. I read forum threads I did not understand about resonant frequencies, analogies to car suspensions on trucks, or vice versa, and debates about physics and engineering formulas, without figuring out how the mismatch was supposed to manifest in the sound I would hear.
I closely followed the cartridge alignment instructions on the Soundsmith website, paying particular attention to anti-skate (had to remove some of the weight from the thread) and azimuth, and tinkered with VTA with some albums suggested on these forums so that the highs were not sibilant and base not flabby. I have yet to hear any ill effects of the guaranteed mismatch. In fact, I would not have believed that a change in turntables could have made such a difference, particularly in surface noise. I am listening to albums I had pretty much given up on.
There might be sonic gremlins that my system is not resolving enough to uncover. If that's the case, fine. Meanwhile, I'll let the Ohm Walsh 4's and REL subs kick some Talking Heads throughout the house.
Steve
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Korf Audio have an interesting take on it, there ae 4 blog posts and a handy calculator. http://korfaudio.com/blog67Using the Ortofon calculations my 18g Schröder with an SPU Royal N should resonate at around 10Hz, on a HFN test record it actually throws a wobble at 7Hz lateral but nothing at 6 or 8Hz vertically, nor at any other frequency for that matter. As above, use a Rega cartridge with a Rega arm and you won’t go wrong, they’re made for each other. |
As one engineer to another we can communicate with each other in technical terms and understand each other. The great beauty of science. In layman's terms my explanation of the matter has left you with an inability to track my thought process. We need to increase your compliance to see this philosophically. :-) Not everybody as the scientific method at their fingertips.
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Actually bill, non compliance manifests itself as feedback, poor tracking and the stylus hopping right out of the groove.
Skip, lewm and chakster have it right. Chakster's suggestion about the HI FI News Analog Test LP is very important. You have a light medium arm.
It will match up well with the more compliant moving magnet cartridges like anything from Audio Technica, Clear Audio or Goldring. The Goldring 1042 is a favorite of mine.
Compliance is a measure of the stiffness of the cantilever's suspension. It is analogous to an automotive suspension. Lets use a pickup truck as an example. Empty pickups (no load) have a choppy ride but if you load one up with a ton of brick the truck now wallows and bounces at a low frequency. That is it's resonance frequency. Add weight the resonance frequency drops, take off weight and the resonance frequency rises. The test record will tell you where your resonance frequency is. If it is too high you add a little weight to the head shell. If the cartridge is too heavy or the compliance to high the resonance frequency will be too low and you would have to remove weight (mass) which can be hard to do. So, it is better to start with a cartridge that might be on the stiff side as you can always add weight. But, any of the above moving magnet cartridges will be just fine. If you tell me how much you want to spend and I'll tell you which models to look at. |
Perhaps you will indulge me a little poetic license. I assure you this is pertinent, not crazy stuff. A person says something that is totally outrageous. A listener accepts the message at face value without reservation. That is compliance. Second scenario: A person says something that is factual and provable. A listener rejects the message resolutely and without qualification. That is non-compliance. As applied to phono playback, any given cartridge/arm combination traces a record groove. Does it comply? How well? What do you hear? Clues that the combination is not fully complying with the requirements would be sibilance and similar forms of unnatural sound. The violin, human voice, and piano are three extraordinarily difficult instruments to accurately record and reproduce.
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Words of wisdom, short and sweet:
Rega table.
Get a Rega cartridge that's in your budget-simple. Enjoy records.
The more you find out, the more unnecessary audio neurosis you'll develop.
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compliance relates to the stiffness of the cantilever and suspension.
a higher compliance is more flexible. lower compliance is stiffer.
if you have a heavy truck you would want a stiffer suspension for more stability. if the suspension was too flexible the truck would lean and sway on the road.
an overly stiff suspension on a light car would also be unstable because the tires could lose contact with the road if it was bumpy.
a low mass tonearm would be a bad match with a stiff, low compliance cartridge because trackability could suffer.
a high mass tonearm would be a bad match with a flexible high compliance cartridge because the position of the stylus would be fighting against the higher inertia of the heavier tonearm, e.g. the suspension could be over stressed trying to track a warped record.
soundsmith has a very good chart that matches cartridges of diffrrent compliances to a range of tonearm masses. |
The matching of cartridge compliance to tonearm effective mass is quite "plastic", in that there is a lot of room to make them match, if you use the standard goal of achieving a resonant frequency of 8 to 12Hz. Plus, in the modern era, we are inundated with "medium mass" tonearms and cartridges with manageable compliance numbers, so for the most part if you are using new OEM stuff, you needn't worry too much. MC, who discounts the importance, actually uses a tonearm that matches well with his cartridge, which is maybe why he can say he pays no attention to the issue. If you look at the equation for the resonant frequency (Fr), it depends inversely upon the square-root of the product of tonearm mass, M, multiplied by the cartridge compliance, C, at 10Hz, as Chak says. If you go on line and look up one of the calculators for Fr, you can fool around with the values for M and C and quickly see there is a lot of room for varying one vs the other parameter and still being in the OK range. This is because you are taking the square-root of the product of those two parameters, which mathematically jams the result into a narrower band of values that tend to produce an acceptable outcome.
By the way, "weight" as we commonly use the word, has little to do with the calculation. "Effective mass" is a product of the distribution of the mass of the tonearm, starting from the counter-weight to the pivot, and from the pivot to the headshell and cartridge, to include the mass of the cartridge and the mounting hardware. Don't knock yourself out with this stuff. Probably your Rega tonearm is in the broad category of "medium mass". Then it depends upon how much your cartridge adds to M and what is its C.
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Rega table.
Get a Rega cartridge that's in your budget-simple. Enjoy records.
The more you find out, the more unnecessary audio neurosis you'll develop. |
Buy a HI-Fi NEWS TEST LP and measure your actual tonearm cartridge combo, you will see where is the resonance frequency really is. "
Tracks 2 & 3: Cartridge & Arm, Lateral & Vertical Resonance Test These two tracks are used to test the resonant frequency or your tonearm and cartridge combination in both the vertical and horizontal domains. These tracks offer both a visual and auditory indication of the resonant frequency; the stylus will “wobble” and the test tone will warble. A resonant frequency between 8 - 15Hz is ideal.'" |
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Stylus not stylist....oops. |
Calculation work ONLY if you know dynamic compliance at 10Hz.
If you cartridge is Japanese then compliance most likely stated at 100Hz in the manual (even if they do not mention 100Hz). In this situation you have to multiply this data on 1.7 at least (to convert it to 10Hz). |
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Believe it or not there once was a time I believed in all that same nonsense. It took years to understand what a waste of time it was learning all that stuff. Now I know to buy a good arm, and buy a good cartridge, and that in both cases "good" is determined entirely by how they sound. Could not even begin to tell you the mass, compliance, or any of that about my last two arms and last three cartridges. What I can tell you though is what really matters: they were medium output, .4mV to .7mV, which made them real easy to match up with a phono stage.
So the one thing that I know matters, output, is the one thing you're not asking about. And the one thing you are asking about, compliance, is the one thing I know does not matter.
Situation normal.
Oh and if you want a good stylist, I recommend Gene Juarez. |
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If you have a heavy tonearm you want a stylist system that can handle the mass of the tonearm. Or if you have a light tonearm you want one that moves easily. Compliance is just a way to match the tonearm weight for best performance. |
