SME V reasonant frequency.

[Wakefield Turntables]

After faffing around with the possibility of a new MC I decided to turn my attention to see what my current tonearm resonance frequency was. Please correct me if any of this is wrong but this is my understanding of this subject.

1. You need to quantify tonearm mass. So mine is a SME V weighing somewhere bewteen 10-11g, low mass in other words.

2. cartridge mass needs to be quantifed. In this case a AudioTechnica oc9 MLII weighing in at 9g

3. You need dynamic compliance of the cartridge, in this case 9 mm/N.

Now i used a freely available resonance calculator and got a frequency resonance of 10.3942. I take this is perfectly acceptable as on the SME website it states that, "Thus 10-12Hz is the ideal region in which to place the arm/cartridge resonance". So from my understanding the SME V and the OC9 MLII are a very good match :confused: ??

Thanks for your patience.

[sq225917]

Unless you are using a stupid low mass arm like an SME 3 or an uber stiff cart it's really not worth worrying about these days. Combinations with resonance below 6hz and above 20hz are very few and far between.

[Wakefield Turntables]

Nope as stated its a SME V, I simply did this as an excercise in trying to better understand my deck, tonearm and cartridge selection

[DSJR]

Simon's right - PLEASE don't worry about it these days. The SME V isn't as massy as it looks (I think) and the OC9 is supremely kind and pretty stable I think, so just enjoy the music it makes...

One cartridge I own which is all but impossible to use on modern vinyl cuts is my ADC 26. Even with a NOS stylus assembly, the thing is unstable at any tracking weight and an SME III with the tiniest amount of damping may be the only option. Not that I'm intending going that way though, but I might try it in the SME II "Improved" fixed head arm at some point.

[Neil McCauley]

Slightly off-topic but helpful I hope.

Some 3 years back, wanting to get definitive information and guidance on the precise subject of how to calculate from first principles what the true ‘effective mass’ of a tonearm was, it was I felt both logical and sensible to talk directly to the team leader of design at SME. This was not Mr. Robertson-Aikman incidentally.

As you might expect from a quintessentially charming company, their response was very courteous. After a period of time though they concluded that their ‘take’ on the subject and the “3 pages” of mathematics involved could not in any realistic sense be converted into a readable and worthwhile article for my target market i.e the general reader. They were concerned that this might confuse rather than enlighten. I abandoned with good grace that proposed article.

I must point out that at no point did I feel that SME were looking to be secretive.

Reading between the lines I formed the distinct impression that there was no consistent approach between experts on precisely what ‘effective mass’ truly meant and therefore the approach to the mathematics was one of inconsistency between the truly great arm-maskers. Hope this helps.

Regards

Howard

PS. Interesting photo/image/avatar. My French teacher's father was a deeply unfortunate disciple of 'The Beast' aka Mr. Crowley.


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[Barry]

After faffing around with the possibility of a new MC I decided to turn my attention to see what my current tonearm resonance frequency was. Please correct me if any of this is wrong but this is my understanding of this subject.

1. You need to quantify tonearm mass. So mine is a SME V weighing somewhere bewteen 10-11g, low mass in other words.

2. cartridge mass needs to be quantifed. In this case a AudioTechnica oc9 MLII weighing in at 9g

3. You need dynamic compliance of the cartridge, in this case 9 mm/N.

Now i used a freely available resonance calculator and got a frequency resonance of 10.3942. I take this is perfectly acceptable as on the SME website it states that, "Thus 10-12Hz is the ideal region in which to place the arm/cartridge resonance". So from my understanding the SME V and the OC9 MLII are a very good match :confused: ??

Thanks for your patience.

According to my calculations, the cartridge-arm resonant frequency is 11.9Hz.

Total effective mass = 10.5g (for the arm) + 9.5g (for the cartridge and fixings)

Compliance = 9 mm/N = 9*e-6 cm/dyne

Thus 1/(2*pi*sqrt((10.5+9.5)*(9*e-6)) = 11.86Hz

But as others have said, don't worry about this the Audio Technica OC9 will work perfectly well in the SME V.

[Barry]

The effective mass of a pickup arm is the moment of inertia about the arm's pivot point divided by the square of the effective arm length.

The moment of inertia can be calcutated given the dimensions of the components making up the arm, the material they are made from and their disposition, according to the geometrical design of the arm.

I performed such a calculation for a fellow member for the home-made unipivot arm he had made: http://theartofsound.net/forum/showthread.php?t=7873&page=3&highlight=moment+inertia. The calculations took 9 pages and even then I had to make some assumptions.

One problem is what is meant by the effective arm length? Usually this is assumed to be the distance between the arm pivot and the stylus. But since the arm-cartridge resonance is due to the mechanical spring-mass system so formed, the distance should be between the arm pivot and the stylus cantilever suspension. The latter is somewhat ambigious, as the suspension point is unclear.

Even so these assumptions and the calculation made thereupon are sufficiently good enough to ascertain the resonant frequency lies within the 'safety zone', 8 -13Hz: above that of foot falls and below the lowest frequency cut onto the record.

[Wakefield Turntables]

Barry,

Thanks for taking the time out mate for doing the calculations! I managed to find an old Xcel spreadsheet which helped me do the hardwork :eyebrows:. I think we get differing frequency values because I probably didnt include the weight of the cartridge fixings and maybe added a slightly differing value for the V's mass. Not to worry!! It appears that we get a value somewhere in the safety zone of 8-13 Hz. It seems that these calculations are probably more applicable to my SME 3009 & Garrard 301!!! :lol: