New Tonearm

[Ammonite Audio]

You need to getting away from the 5Hz region

Dear God! How much mass would you need to even get down to 8Hz, let alone 5Hz? Actually, and according to http://www.resfreq.com/resonancecalculator.html the answer (if we take AT's compliance figure as correct) would be a total arm effective mass + cartridge mass of 101g!

[Snoopdog]

Hugo,

According to the Ortofon pick up test record I use "Any combination of a tonearm and a cartridge will have a resonance frequency which will typically appear in the subsonic range between 4 and 15Hz. Although a resonance frequency below 20Hz is inaudible in itself, it is very important for other reasons that it does not occur in a range that can influence the reproduction of records. Below 5Hz, all records contain warps and other irregularities. If the tonearm resonance frequency is much lower than 8Hz, the record warps can excite resonance and the audible results can be increased rumble, reduced tracking ability ansd a marked sensitivity to acoustical feedback. Therefore the resonance frequency should be higher than 8Hz (preferably in the 10-12Hz range), but not so high as to appear in the audio spectrum above 20Hz."

I manage 9.5Hz with my Phantom/Orpheus combination.

[Rare Bird]

Dear God! How much mass would you need to even get down to 8Hz, let alone 5Hz? Actually, and according to http://www.resfreq.com/resonancecalculator.html the answer (if we take AT's compliance figure as correct) would be a total arm effective mass + cartridge mass of 101g!

You need to do your sums again

[Ammonite Audio]

Andre, the the guidance and calculators at http://www.resfreq.com/resonancecalculator.html and Vinyl Engine do agree on the calculations, although it's a wholly theoretical scenario to contemplate a resonant frequency that low.

The resfreq site does explain the 100Hz dynamic compliance thing, though:

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)

On that basis, the actual 10Hz dynamic compliance of the AT33PTG is 13cu, which means a combined resonant frequency of a whisker under 10Hz in the Ittok without added mass, which is rather similar to Steve's Orpheus/Phantom; and which ought to be OK. My added 6g takes it down to around 8.5Hz, which does seem to result in a more dynamic, tuneful sound, to my ears at least. When my mate Tony comes round next I shall let him hear it with and without the added mass and take note of what he says, since he's usually right with these things!

[Rare Bird]

Andre, the the guidance and calculators at http://www.resfreq.com/resonancecalculator.html and Vinyl Engine do agree on the calculations, although it's a wholly theoretical scenario to contemplate a resonant frequency that low.

The resfreq site does explain the 100Hz dynamic compliance thing, though:



On that basis, the actual 10Hz dynamic compliance of the AT33PTG is 13cu, which means a combined resonant frequency of a whisker under 10Hz in the Ittok without added mass, which is rather similar to Steve's Orpheus/Phantom; and which ought to be OK. My added 6g takes it down to around 8.5Hz, which does seem to result in a more dynamic, tuneful sound, to my ears at least. When my mate Tony comes round next I shall let him hear it with and without the added mass and take note of what he says, since he's usually right with these things!

Can you give me the cartridge weight & compliance please as i'm not getting that calculation, i'm assuming the arm has a mass of 13.5g !we'll allow 0.5g for the fastners..Tis an area i have zero intrest in but i'm now intrigued..

[Ammonite Audio]

Arm effective mass + cartridge mass = 13.5g + 6.8g = 20.3g total system mass, not including fasteners.
Compliance of the AT33PTG is 10 x 10-6cm/Dyne at 100Hz, which equates to 13 x 10-6cm/Dyne at 10Hz, according to the guidance at the resfreq site.

I must say that until now I have paid scant attention to this subject, and it's most illuminating! I have found out several useful things today.

[Rare Bird]

Arm effective mass + cartridge mass = 13.5g + 6.8g = 20.3g total system mass, not including fasteners.
Compliance of the AT33PTG is 10 x 10-6cm/Dyne at 100Hz, which equates to 13 x 10-6cm/Dyne at 10Hz, according to the guidance at the resfreq site.

I must say that until now I have paid scant attention to this subject, and it's most illuminating! I have found out several useful things today.

I get a resonant Frequence of 11Hz allowing 0.5g for fasterning hardware. I don't honestly see why you want to add more mass that is quite satisfactory. Adding a couple gramm to the arm mass will hardly move it enough to notice!

[Ammonite Audio]

I add a bit more mass because it sounds better, to my ears. Simples!

[DSJR]

I have an old friend who started the whole Infra-Bass thing in the mid seventies. he preferred to load up an ADC XLM II in a Sansui 717 direct drive, the resulting resonance well below 5Hz. No stability problems with his records and the sound did improve - in his strange system...

10Hz to me is still a touch high, and if adding mass to the well damped AT helps, then go for it IMO. I haven't done this to the Stilton OC9, as the replaced mount seems heavy enough. the Dual's sprung counterweight deals with the rest.

What you DON'T want, is a massive bass rise which overloads the phono stage, any more than a severe top end resonance, whatever the frequency, otherwise it takes off like a Rega Apheta without the added eq to tame it...

[DSJR]

Not nececelery Andr'e.... Not simples