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Post by Deleted on Jun 26, 2017 17:27:29 GMT
I had assumed Jules' arm was the original Stogi. Assuming Karney did his original sums right that would put the total effective mass at 19.5g of which 6.8g was the cartridge and the effective mass of the original stoogi would be 12.7g - oops , less the fixings = 12.2g That would make the resonant frequency 8.5Hz - still comfortable We are assuming the mass of the cartridge is centred on the stylus tip in simply adding the cartridge mass to the arm effective mass to give total effective mass, and you can get too pseudo-precise with these things. 7-12Hz is the safe range according to Ortofon, and that's close enough for Jazz. I still get 11.4Hz with the original Stogi!
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Post by pinkie on Jun 26, 2017 18:21:35 GMT
How do you get 11Hz with 18cu for the cartridge
The formula is 1000/sgr(MxC)*2Pi so sqr(18x18)=18 2Pi is near enough 6.3 1000/(6.3*18) = 8.8 call it 9 for cash.
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Post by ChrisB on Jun 26, 2017 18:34:37 GMT
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Post by pinkie on Jun 26, 2017 18:56:18 GMT
A bit of rounding rarely hurts in regular domestic life. As Martin's arm demonstrates these rules are an imprecise science. Measure to the nearest half-brick.
I was sad enough at school to learn pi as 3.14159265359 by heart. It never seemed to impress the girls though.
Sue needed to work out the circumference of plant pot holders recently and I told her pi was 3
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Post by MartinT on Jun 26, 2017 19:03:22 GMT
Pi would have henceforth been 3.2? Only politicians could get the rounding wrong!
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Post by Deleted on Jun 26, 2017 19:18:05 GMT
& how did you come to that result?? I confess, I relied on your information for the arm and cartridge mass - 11+7gm = 18gm I rounded up the mid-point of 1.5 times and 2 times the 100Hz cu figure of 10cu to give 18cu at 10Hz The formula is 1000/sgr(MxC)*2Pi so sqr(18x18)=18 2Pi is near enough 6.3 1000/(6.3*18) = 8.8 call it 9 for cash. Ok just looked up four different calculatiors, all say appox 11.4Hz
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Post by pinkie on Jun 27, 2017 7:31:13 GMT
That's a screenshot from the site Slinger linked to on the 4th post in this thread. Total mass of cartridge and arm 18g Cartridge compliance 18cu Resonance 8.842 Hz Either the calculators you are using don't calculate properly, or you are putting the wrong numbers in. I gave you the formula, and did the calculation showing my workings. I don't know how else to help you If you are getting 11Hz either you have too low a compliance number (its too stiff) or too low an effective mass
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Post by Deleted on Jun 28, 2017 14:20:52 GMT
Cartridge compliance 18cu! Thought it was 10cu?
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Post by pinkie on Jun 28, 2017 14:53:50 GMT
Cartridge compliance 18cu! Thought it was 10cu? That is the whole point of the thread. My earlier post (the 7th of this thread) dealt with the OP's original question (Oh for post numbering ) Compliance varies with frequency. For the purpose of this exercise we want to know the dynamic compliance at between 5 and 20Hz. The dynamic compliance at 10Hz will do well enough, and is quoted by many UK and European manufacturers. Japanese manufacturers often quote it at 100Hz Some cartridge manufacturers quote static compliance To use the calculators you need to supply the dynamic compliance at 10Hz. Read the warning above the site Slinger linked to and I pasted a screenshot from "There is one snag about it. The manufacturers of cartridges do not always state a useful value for C(ompliance). (It should be started at 10 Hz). Figures of C coming from Japan usually are measured at 100 Hz, so they should be multiplied by 1.5-2. Figures of C coming from USA often are static values, so they should be halved. Most figures of C coming from Europe are OK (stated at 10 Hz)" (Actually - if I'd read that in the first place it would have saved a lot of typing. It repeats, near enough, what I told Jules, and learned at Arthur's knee) It's not possible to convert with accuracy, but generally the dynamic compliance at 10Hz is between 1.5 times and 2 times the figure at 100Hz. That is why Jules asked for the conversion information in the first place. So, I took the midpoint between them of 17.5cu and rounded it up to 18cu. It's close enough for these purposes
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