Resonant Frequency

This is to whet your appetite.On page 14 of the aforementioned paper."Since we have to conclude that practical records contain a large amount of "rubbish" centered around 4-5hz including warps,the optimum solution is clear.The tonearm/cartridge resonance has to be placed at such a high frequency 13-18hz that it mechanically filters out the subsonic signals.In addition some damping should be applied to eliminate oscillations and influence above 20hz" Stefanl

Stefanl,

Did I forget the ultimate mod?

This interesting subject on resonance frequency has been forgotten since the 80's. Within this thread we discovered that we all are very unsure about the real pre's and cons. Much can be read on VTA and azymuth for instance, but nobody really knows what the right frequency range will be for the resonance of your arm/ cartridge- combo.

That's why several hifi- manufacturers(Rega, Shure, Audio Technica)of arms and cartridges have skipped effective mass and compliance from their spec lists. And that's why in forums like this we read about so many midrange-mass or heavy-mass arms with Shure V15- cartrtidges in it for instance! We should make ourselves a bit more emancipated on this issue, IMO.

Perhaps the paper that can be downloaded at Vinyl Engine has been digged it up somewhere in Egypt, but it seems that nobody ever had read it. Did you download it already from overthere? (from V.Engine that is!) This paper has received diverse reactions in the discussions. But it states, that when you increase the resonance frequency higher and higher above 10Hz, you are continuously improving on tracking stability. Not much respected literature could be found until now on this subject.

The real problem is: can we get a BIT high? Or: how can we prevent that it will become too LOW? Several visit to forums have learned me that perhaps in only 10 % of the cases there is a resonance frequency of 12 Hz or above. I guess 30 % is between 10 and 12 Hz and the rest, 60 % is below 10 Hz!

Low resonance frequencies are not a favourable frequency at all. In several HiFi Choice reviews that I read, they said that an 8 Hz frequency will interfere badly with the resonance frequency of your subchassis and with warps, excentricity and other rubbish on your disc. Moreover, this increases sensitivity for footfall and airborne playback- disturbance. It really starts to get stable above 10Hz, believe me. People who found their vision on years of experience will see this vision belied by the plain rules of nature. These rules do not tolerate mockery. Really, 6 Hz is disastrous and the commonly met 7.5 Hz. should never be worth your budget!

As you already discovered, your nicely crafted Rega arm (splendid thing IMO) is not really a lightweight model. Real light rascals are for instance a SME 3009 Improved II with non- detachable headshell. That is a good one too, but weighs in at 6 g. So nearly half of the Rega. So is the Rega a bad one? NO!

The worst cases are to behold, where the our famous Shures get on stage. Are they bad? NOOOOOOOOH! But they have compliances from 25 to 35 cu. Is that too high? NOOOOOOH! But too high for the arms found at Technics 1200 or for other s- shaped japanese arms. Are these arm bad? NOOOOOOOH!

So when you would have a SME 3009 II Improved with detachable headshell and put a Shure V15 _ V xMR in it, the resonace will not be at 8 Hz or above. And this is not favourable at all. Why not?

The bad influences will be detected as:

*Peak signals in music become less clean.

*Nasty short-term fluctuations of tracking force, causing loss of tracking ability of complex passages in the music. You will not be able any more to hear the fine strands within complex mixes of instruments and or voices.

*Decreased resistance to footfall.

*Decreased tracking stability when playing records with warpes or excentricity, such as found among the many second hand discs bought by vinyl lovers today

*Increased record wear caused by a larger number of minor or serious cases of mistracking.

*the internal resonance behavior of a turntable can be disturbed because the arm resonance may interfere with the subchassis resonance. So the common vitues of such a design will be harmed Like adequate isolation from motor rumble.

If you have no problems with these drawbacks, then that it is ok with me. But why did you purchase those costly products when after all these effects do not bother you? And why do so many users say to themselves: I fear that my motor causes wow. So I plan to purchase a motor mod seen at site blablabla.com. Sombody else likes his arm to have a bronze knife edge mod costing blablabla usd. Perhaps your neighbour has installed a costly Grado cartridge together with a vintage EMT arm on his motor unit. In all these cases the arm/ cartridge combo CAN be faulty already, certainly in the last case!

To these people I say: You forgot the most important and cheapest mod: putting the resonance frequency at least at 10Hz. It does not cost a penny more and it pays back generously in musical terms!

When you will have these resonance frequencies above 10Hz (just try to reach them first) there will only be little bass boost. Organ tones will drop as dramatically as fig. 7 of the danish paper shows! And believe me: this same paper clearly proves that the resonance frequency has no high harmonics at all! Did you read the paper? And the lowest notes do not have lower harminics. All nonsense.

So there really is are perfect resonance frequencies: as high as possible! But what is more important: there is too little knowledge on this subject. So there is too much damage caused by badly chosen combinations. I want to challenge you all: when it does not matter do not hesitate to put a mass upon your headshell, bonded to it by means of BluTack. Take 6 g. for this as a starting point. Please be honest to yourself. And reset yr tracking force to the same low value as you normally apply. Play a record with humble warps with this new assembly. I would like to know if your new set will play complex parts of the inner track as good throught your headset as the normal setup. When the musical result is the same for most of you, I will withdwraw my entire plea! But note, that the more expensive your layout will be, the more dramatic the quality drop will show up!

Let us be happy with those low- compliance- carts like Ortofon MC’s. Sound is pleasant and tracking is stable in several arms. These models own a kind of universal appliccability, which will never be gained by any Shure. IMO: MC’s are even the best choices at the higher budgets.

Let’s return to the pure basically right electroacoustic technology. And after that we can serch for our own preferences among those modern expensive mod tricks, which serve so many times to solve problems, which would not have been there, when we had chosen for the suitable arm/ cart/ combinations in the first place.

Great to see your post explaining the issues involved janvoorn! I have done some thinking on this and it occurred to me that with the Rega arm for instance,the most popular cartridges for it, that seem to come up time and again on this and other forums, are the Sumiko Blue Point Special and the Dynavector 10x5.I calculated the rf for these and they both come out at almost exactly 10hz.My Ortofon again recommended favourably, is almost exactly 11hz.I read an argument on Vinyl Asylum supporting 8 hz optimum but the reasoning seemed strange,The bass response apparantly sounds too "fat" at 10hz.But this could be a function of the mat or VTA.Preferring a thinner sound is a path many have travelled re.higher volumes and digital sound colouring tastes,esoteric rock etc.,so I am wary.Again the success of the aforementioned cartridges is a strong argument.Stefanl

I am really digging this thread, and thank you Stefanl and JanVoorn for your comments. I have found an interesting piece that references the 1977 AES paper of Ladegaard - to wit: Multidimensional Audio, by Henning Moller, Bruel & Kjaer.

It is located here: http://www.zainea.com/multidimensionalaudio.htm

As I understand it, the author is making the case for the higher RF, say 10Hz-14Hz, in part, b/c it will not interfere with record eccentricities and the actual resonance of the turntables suspension. But we should perhaps agree that a decent enough suspended table will have its resonance somewhere between the 3 and 4Hz range, blocking for certain footfall induced and other resonances above 4Hz. It will also then provide very good acoustic isolation.

I will have to do as JanVoorn suggests and test this in practice. Setting the low frequency limit of the turntable to 8Hz versus say 10 or even 12Hz seems like a fairly reasonable place...more after I find and read the entire AES paper, but the point that we NEED to sort of tackle this issue and publish a guide of sorts is not lost on me. I agree - nobody seems to be giving this any attention and of course manufacturer's are doing nothing to recommend particular combinations of arms and cartridges based in part on their own testing with respect to RF and its effects on the optimum performace, at least not to my knowledge.

I did get a Shure engineer to narrow down the effective mass of the arm they recommend for the V15VxMR, and I have measured (as opposed to calculated) a 9Hz horizontal and 10Hz vertical resonance with the V15VxMR on an SME IV arm, stabilizer brush up.

This is a lower medium mass arm (10-11g acc to SME). Certainly not what we are lead to believe as optimum considering the alleged high compliance of the cartridge.

I have NEVER heard the Shure sound as good as it did on my SMEIV....

Here is the piece I referenced above, sans graphs:

"5. Audible Effects of Wow and Flutter, Rumble, Tone Arm Resonances etc.



The Transient Distortion (section 4) was an example of how the high frequency domain influences the music domain by creating products that fall down into the audible range. This section will consider a similar effect from the low frequency domain that creates serious problems in the music domain by modulating the signals. In other words, the effect of subsonic signals folding up into the audible range (dare we call it BIM - Bass Intermodulation Distortion). Also here it is often heard that people say "I cannot hear 10 Hz, so I do not care". Again it is true that 10 Hz cannot be heard directly, but the effect of 10 Hz, however, is certainly audible. Some of these pheno­mena are illustrated in Fig.7.

The curve in the upper left hand corner of the figure shows a straight­forward frequency analysis of the low frequency range 2 Hz - 60 Hz produced by an ordinary turntable with preamplifier. The most severe peak is produced by the mechanical resonance of the tone arm and the stylus, but motor rumble and hum is also clearly visible. Unfortunately, the tone arm resonance has a level typically only 10-20 dB lower than the signal produced simulatenously in the audible range.

This effect is indicated on the right hand side of Fig.7. Although the low frequency signals are not di­rectly audible, they produce some clearly audible sidebands on the music signals. Also in this domain, the effect is typically 10% distortion. The most critical range of this is known from the wow and flutter weighting function which is most sensitive around 4 Hz. So really the closer the tone arm resonance is to 4 Hz, the worse the audible effect. A frequency analysis of the demodulated wow and flutter signal is also an interesting measurement of the phenomena. A typical result of this using the automatic B & K Wow and Flutter Meter 6203 is shown in the lower left hand corner of Fig.7.

The pronounced resonance at 0,61-1z is due to wrong centring of the record. It is a paradox that often we think we measure wow and flutter when in reality we are measuring the influence of the tone arm cartridge combination. It does not help to improve the turntable motor mechanism when it is the tone arm resonance that is creating the problem.

Unfortunately, the mechanical resonances in tone arms are excited all the time by the warps in the records. The effect seen in the time domain is a ringing that sometimes goes on for half a revolution of the record and also affects the tracking force so it changes from near nothing to twice the "steady state' tracking force.

An interesting test of this can be made simply by making a cut in the record and offsetting the two parts. Every time the stylus passes the

"step-function" a transient is produced. A recording on a storage scope or the B & K Narrow Band Analyzer 2031 will show the time function or the time and frequency functions respectively. A typical result of different time responses for different tone arms with the same cartridge is shown in Fig.8.

The phenomena of audible effects of mechanical resonances in turntables are described in further detail in the B & K Application Note 17-233 (Ref.7). The audible effect of the phenomena again is a "frequency smear" or a "confusion effect" of the sound picture."