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Post by julesd68 on Jun 21, 2017 21:36:13 GMT
If my cartridge has quoted Dynamic Compliance 10×10-6cm/dyne at 100Hz what would that be at 10Hz??
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Post by MartinT on Jun 21, 2017 21:47:58 GMT
That's a low compliance so the rule of thumb suggests it would need a heavy arm otherwise the resonant frequency will be too high. In other words, give it a heavy arm for good bass.
Generally speaking, of course.
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Post by julesd68 on Jun 21, 2017 22:38:19 GMT
Sure I'm with that, but was wondering what the exact figure would be at 10hz?
My Kuzma rates as medium mass but does sound fine. Interesting to hear that I could possibly get improved bass from a high mass arm. That is appealing...
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Post by Slinger on Jun 22, 2017 0:03:09 GMT
Is this of any use to you Jules?
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Post by Deleted on Jun 22, 2017 3:43:22 GMT
If my cartridge has quoted Dynamic Compliance 10×10-6cm/dyne at 100Hz what would that be at 10Hz?? Im assuming your Kuzma arm is the later 'Stogi 'S'? .. Approx 11.8Hz Res Frequency, If its the original 'Stogi' 11.4Hz..Which is fine.. Arm: 11g Cart: 6.8g Cart Compliance: 10 mm/uN Fixings: 0.5g
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Post by MartinT on Jun 22, 2017 5:27:33 GMT
Interesting to hear that I could possibly get improved bass from a high mass arm. Honestly, I doubt you could improve on the Kuzma unless you can add damping.
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Post by pinkie on Jun 22, 2017 5:38:13 GMT
There is no definitive formula to convert dynamic cu at 100 Hz to dynamic cu at 10hz, but the rule of thumb I used was multiply by 1.5. it could be as much as multiply by 2. If it's ok in that range it's probably ok. 1.8 times would be 18 cu which puts your system resonance at about 8.8hz which is fine. If the real cu is higher then a bit less effective mass would be preferred.
At least you only have to worry about one effective mass assumed to be the same horizontal as vertical. Poor old Martin has to cope with very low vertical effective mass and very high horizontal effective mass. Not many cartridges quote differential vertical and horizontal cu
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Post by pinkie on Jun 22, 2017 5:43:24 GMT
Interesting to hear that I could possibly get improved bass from a high mass arm. Honestly, I doubt you could improve on the Kuzma unless you can add damping. I don't know where to start. Avoid damping - if you wanted to lower the resonant frequency add mass at the headshell. More mass would not help bass Too much mass would put you near to the trouble zone for record warps You don't want to add mass.
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Post by MartinT on Jun 22, 2017 6:18:34 GMT
I agree that heavy arms do not normally have damping, although my Dynavector is an exception with eddy current damping.
More effective mass does help bass with a low compliance cartridge. Try a low cu MC in an SME III - I did!
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Post by pinkie on Jun 22, 2017 8:17:42 GMT
Martin, I agree - if you have a stiff cartridge in a low mass arm, then the resonance will shift to the bass frequencies of the audio band (well, harmonics of that resonance will be in the audio band). That may colour and blur the bass - emphasising audible frequencies. So you usually try to keep the resonance below 12Hz although in practice probably 15Hz is not a disaster.
The mistake being made was to think Jules cartridge was stiff, when it was quite springy - because the 100Hz cu was being used in a calculation that needed 10 Hz - which was of course the question he first asked. So he is already comfortably away from the 15Hz audio threshold, and more at risk of tracking problems from record warps etc, (which again in practice, really are down below 5Hz - but the aim is usually to keep the resonance above 8Hz to be safe.) Any more mass, assuming 15-18cu is a good guess for the compliance at 10Hz, and he risks flirting with the 8Hz band
Damping generally is not my favourite thing - nor my chum with the record player businesses favourite thing either.
The Dynavector arm you use has significantly different effective mass in the vertical and horizontal plane, yet presumably lets normal cartridges track OK and doesn't suffer from bass "bloom" . Probably, with a rigid cartridge, and very low vertical effective mass, the resonance for the system in the vertical plane is easily into the audio band above 20Hz, never mind 15Hz. In theory - following your suggestion - this would detract from the bass, but preumably doesn't
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Post by julesd68 on Jun 22, 2017 9:33:55 GMT
There is no definitive formula to convert dynamic cu at 100 Hz to dynamic cu at 10hz, but the rule of thumb I used was multiply by 1.5. it could be as much as multiply by 2. If it's ok in that range it's probably ok. 1.8 times would be 18 cu which puts your system resonance at about 8.8hz which is fine. If the real cu is higher then a bit less effective mass would be preferred. Thank you Richard, that's exactly what I was looking for. Very interesting - so actually I have been in wrong in thinking a higher effective mass arm would be more desirable and my arm is actually a very good technical match for my cart. A conversion factor of 1.5-1.8 puts me right in the sweet zone ... But more importantly, the arm does sound very good indeed!
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Post by julesd68 on Jun 22, 2017 9:35:11 GMT
Is this of any use to you Jules? I've been using the Vinyl Engine 'Cartridge Resonance Evaluator' but that looks useful too, thanks Paul ...
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Post by MartinT on Jun 22, 2017 10:04:01 GMT
The Dynavector arm you use has significantly different effective mass in the vertical and horizontal plane, yet presumably lets normal cartridges track OK and doesn't suffer from bass "bloom" . Probably, with a rigid cartridge, and very low vertical effective mass, the resonance for the system in the vertical plane is easily into the audio band above 20Hz, never mind 15Hz. In theory - following your suggestion - this would detract from the bass, but preumably doesn't My Shelter 5000 has a compliance of 9cu. It tracks very well in the DV, with deep and tight bass and a sense of authority as well as lightning fast dynamics (which Jerry can attest to). It's a heavy cartridge and likes a heavy arm. In the Technics, you may think it's all a bit too much of a good thing but it really isn't, with fantastic soundstage, detail and imaging.
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Post by pinkie on Jun 22, 2017 10:30:52 GMT
The Dynavector arm you use has significantly different effective mass in the vertical and horizontal plane, yet presumably lets normal cartridges track OK and doesn't suffer from bass "bloom" . Probably, with a rigid cartridge, and very low vertical effective mass, the resonance for the system in the vertical plane is easily into the audio band above 20Hz, never mind 15Hz. In theory - following your suggestion - this would detract from the bass, but preumably doesn't My Shelter 5000 has a compliance of 9cu. It tracks very well in the DV, with deep and tight bass and a sense of authority as well as lightning fast dynamics (which Jerry can attest to). It's a heavy cartridge and likes a heavy arm. In the Technics, you may think it's all a bit too much of a good thing but it really isn't, with fantastic soundstage, detail and imaging. Compliance, and effective mass, are both relevant in horizontal and vertical planes. With the notable exception of the Decca Londons, most cartridges have (very nearly) identical vertical and horizontal compliance. Without having the facility to measure I would bet the ranch that the Shelter has 9cu in both planes. Without looking it up, since it is Japanese, that is probably a dynamic compliance at 100Hz, so the 10Hz figure would be in the 14-18 range. Effective mass is not weight. Again - no time to look it up, but its to do with a fulcrum - its the force needed to deflect. Most arms, with bearings at nearly the same point, and of nearly the same resistance, both vertically and horizontally, have nearly the same effective mass in both horizontal and vertical planes. The Dynavector has a bloody great beam with huge effective mass on its horizontal bearings, and a fly-weight, short low effective mass sub-arm for the vertical movement. So your arm is only "heavy" horizontally - it is "light as a feather" vertically. ( I had the values somewhere, but in the move to France I have no idea where they are . His lordship would probably know if I asked him)
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Post by MartinT on Jun 22, 2017 11:09:26 GMT
Yes, I know that. My point was that it sounds great despite the very different effective mass in the vertical and horizontal planes. DV's explanation of the beam being an 'immovable object' horizontally and the stub-arm being very light to move in the vertical plane is to aid the tracking of warps while capturing everything in the groove. For mono, highly stable tracking is easy to grasp. Since stereo comprises two 45 degree groove walls, the interaction of the two defeats my brain at the moment.
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Post by Deleted on Jun 22, 2017 12:09:06 GMT
which puts your system resonance at about 8.8hz which is fine. & how did you come to that result??
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Post by pinkie on Jun 23, 2017 7:17:29 GMT
which puts your system resonance at about 8.8hz which is fine. & 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.
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Post by ChrisB on Jun 23, 2017 7:24:56 GMT
I had assumed Jules' arm was the original Stogi.
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Post by pinkie on Jun 23, 2017 9:02:40 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.
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Post by julesd68 on Jun 23, 2017 9:34:02 GMT
I had assumed Jules' arm was the original Stogi. It is indeed - there have been various incarnations of this arm but I believe effective mass is 12.5g
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