I have had some pumping woofer problems and have looked at isolating my turntable to try and stop this. However, something made me think yesterday, I'll explain. A guy from one of the other forums I am on brought his turntable around so I could help him set it up. Now, while his TT did not sound great (it sounded like the music was being played in a small box and lacked dynamism and clarity (also had tracking problems on one record mine tracked fine) - any suggestions what this might be, I think it might be his cart) but there was one interesting factor. No woofer pumping, even at high volumes where I get plenty.
Now, the turntables are quite different. His is a Yamaha PF800 and is a suspended deck while my Micro Seiki MR611 is not suspended. His deck also weighs more. However, the fact there was no woofer pumping got me thinking.
My problem is that I cannot find out anywhere what the effective mass of my tonearm is. The arm is a Micro Seiki MA101II. There is quite a bit of information on the 'net but no effective mass figures. I have always assumed that it is medium mass. My current cart has a dynamic compliance of 15 and I figured that would be a match. But what if I'm wrong?
Now there is one way to try and work out what the mass of the arm might be. In the manual for the turntable there is mention of the standard cart which comes with the turntable - it is a Micro Seiki VF3200. Now there are a few versions of MS VF3200s but I remember seeing somewhere that my TT was made in 1973, the only VF3200 made before 1973 is the VF3200/E. This cart has a compliance of 30 and weighs 4.5 grams. According to the Cartridge database it is well matched with an arm of an effective mass of 4 to 7 grams. This would seem to indicate that my arm has an effective mass of somewhere between 4 and 7 grams, after all, surely Micro Seiki would make their standard cart a good match with the arm which comes with the TT.
So, my first question is: is this a reasonable supposition?
To the next quandary. My current cart, an Ortofon MC15SuperII, has a dynamic compliance of 15 and weighs 7 grams. It is most suited, according to the cartridge database, to an arm with an effective mass of 6 to 22 grams. This would seem to not be a good match for the arm and may be the cause of the pumping woofers - seem reasonable? Anyway, the chart in the cartridge database indicates that, if the Ortofon was heavier, say about 3 grammes heavier, it would be a better match for a low mass arm. At 10 grammes it would suit an arm of 4 to 19 grammes effective mass.
Which leads to question 2 - if I add weight to the cart, by say (temporarily) blu-tacking a 5cent coin to the headshell, would this be likely to solve the pumping woofers problem? I don't quite understand how this can work given I would also adjust the VTF back to about 1.8 grammes. Maybe I just need an explanation (please avoid maths if possible, if not I'll cope
A third question is - is there a way of working out the effective mass of my tonearm without removing the tonearm?
Lastly, an extra question - what could be causing the problems I described above with my friend's turntable? Any ideas.
My System: Micro Seiki BL51 Turntable, Stax UA7 Tonearm, RCM Sensor Prelude Phono Stage, Ortofon MC15 Super II Cartridge, Rotel RCD865BX Cd Player, Melody I34R (Astro Black 40) amp and Osborn Epitome Speakers.