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I've been listening to this Expressimo RB250 / Shelter 501 II combo for what seems like ages. I just had it aligned with a protractor, its vta tuned by ear and was pretty happy. Nicely detailed sound, hard to characterize any particular trait since the setup seems to change it's tonal character with each new record. That's working good, I thought.BTW, the table is a Teres 145. The all acrylic job with the shot loaded platter.
Anyway, the other day I thought maybe the arm/cart could use some additional tuning. I had never been able to get it to successfully track band 8, side one of the hfnrr test record without at least 'some' buzzing. That's the anti-skate track / torture test. Track 9 was out of the question. So I thought to try some things to maybe improve this score. Watching the lateral and vertical arm/cart resonance test I saw a lateral resonance of 11-12hz. That's good, but the vertical was clearly resonating the arm/cart at 14-hz. That's a bit high, I thought.
The Rega arm has a effective mass rating of 11.5 g and the Shelter cart, stiff little bugger that it is, has a rather non-compliant compliance of 9.....or so someone says. Maybe the compliance is really stiffer than 9 or the rega arm is lighter than 11.5g, but it began to bug me that the vertical resonance was above the desired range ( 8 - 12 hz).
What to do...? Well I thought to add some mass out over the cartridge where it will have maximum influence on the effective mass of the arm/cart system. Looking through the scrap bin I found some 1/64th inch thick lead sheet. I cut a thin strip about 1/4 inch wide in a length to match the circumferance of the arm just before the head shell end. Using black electricians tape, I wrapped the thin lead sheet around the arm, at it's neck, tightly with the tape. No other arm wrap was used.
After resetting vtf, back to the recommended 1.8gram for this cartridge I ran through the tracks on the test record again. This time vertical arm/cart resonance was happening at the upper end of 12-hz. The lateral resonance was wiggling the arm/cart at 9-10hz. Now I had both figures within the recommended ball park. Time to try those anti-skate tracks again.
This time, with a little adjustment made to the anti-skate dial on the rega arm, I was able to get a clean tone with no buzz of any kind through track eight. Track nine is still a fail,loud buzz but the arm/cart tracks through....noisily. Who passes track 9 anyway...!
Long story needs to get shorter so I'll wrap it. Listening test reveal a different tonality with the arm/cart adjusted this way. Overall, it's warmer. Still highly detailed but the highs have more warmth. Low frequencies are still tight but fully extended and with substantial kick and weight. No real gains made to the low frequencies but the highs and mids are certainly less....shall we say...bright...?
Another observation is to watch the needle drops going into the lead-in grooves on various records. Much smoother this way. Watching the cantilever actually display a small amount of compliance where before it was obviously......a stiff little bugger.
Seems like a move in the right direction.
-Steve
Follow Ups:
A very old controversy. To my knowledge the lower resonance frequencies can only add more of a certain kind of distortion : BIM, Bass InterModulation.There is no theoretical background which shows me that the musical reproduction would become better. The only conclusion that I can make is that the alterations will sound better to your own ears in this case, and cannot be called better in an absolute sense.
IMHO one never should add mass to a headshell.
Jan.
That itself adds mass to the headshell. The various combinations of compliance and cartridge weight ranges all over the place. There is no magical one such combination so virtually any cartidge one would use vs. any other will be effectively changing headshell wieght, ie.e mass.
When something is wrong,addition of mass can only be the right cure in my opinion when this mass really appears to have solved the core- problem. Lowering of resonance frequency cannot be seen as a cure in itself.But let's find the real substantial backgrounds of this sonic improvements. I still do not see them...
Jan.
"When something is wrong,addition of mass can only be the right cure in my opinion when this mass really appears to have solved the core- problem. Lowering of resonance frequency cannot be seen as a cure in itself."What the hell does that mean?!
If a certain cartridge/arm combination results in a much too high resonance frequency and another combination is Ok by any test you choose than the only practical solution to the "core problem" of the first combination is to increase the arm mass being that it is pretty impossible for one to increase the compliance or mass of the cartridge.
So where's the problem?
"If a certain cartridge/arm combination results in a much too high resonance frequency" Why can it be too high? To my knowledge the higher resonances give more stable tracking and less BIM. Do you mean a lower resistance against flexing? Then you should locate the core problem in the arm, not in the resonance frequency.
"and another combination is Ok by any test you choose" Perhaps that other combination has other properties than the lower resonance frequency, which overrules the result of it.
"than the only practical solution to the "core problem" of the first combination is to increase the arm mass being that it is pretty impossible for one to increase the compliance or mass of the cartridge." I do not see why a high resonance frequency on it's own can be the cause of bad sonic results.
There must be another problem in the first combination , of which the sound does not convince you. Until now I never have read a substantial theoretic base for the assumtion that a somewhat higher resonance frequency can cause worse musical results. Or it must be that the less favourite artefacts in the sonic panorama have a fatal attraction to you. Overhere we call that the "Radio Modern- Bass" You should visit their shops to experience what I mean.
Or do you have the same conviction: only your feeling for "good or bad" compliances and "good or bad" effective masses is the only and sufficient regular guideline for the assumption that the lower compliances sound better? That will never convince me.
Can't we find really concrete theoretical backgrounds for it? There must be some of them. Let's seek for it!
Jan.
"than the only practical solution to the "core problem" of the first combination is to increase the arm mass being that it is pretty impossible for one to increase the compliance or mass of the cartridge." I do not see why a high resonance frequency on it's own can be the cause of bad sonic results.Well Jan, then you are the only one.
We're not talking her about the difference between 8-12Hz and say 14Hz. I would be the last to say it has to be bwtween 8 and 12.
And for your information there is no relationship between the resonance frequency and the actual frequency contained n a groove modulation. There is probably very little if anything under 40Hz on most records and certainly not under 25Hz.
I still miss concrete backgrounds for your advice to lower resonance frequency. Your "popular" point of view never received any theoretic basis when they launched it in the press nor anywhere else. Convince me like the 1977 AES paper will do..... There simply are no grounds for it..."between the resonance frequency and the actual frequency contained and groove modulation" Where did I say that?
Need not to give it up. I'm not on my own either. Certainly not. I have strong considerations founded on research results. Like I explained so may times. Your theory has missed that until now. Let's seek for it please! Help me out. I like to believe it, but it simply misses the founding facts. It' not done these days to lounch a theory without a strong basis.
Jan
"IMHO one never should add mass to a headshell."In order to accept a statement like the above, one would have to be willing to believe that all tonearms will match up well with all cartridges. And of course that simply is not true.
A cantilever suspension needs to be a compliant match to the weight of the arm it is mounted to so that its suspension takes on the deflection as the stylus negotiates heavier groove modulations within the record. When cantilevers are too stiff for the arm mounted, the entire arm deflects as these groove modulations are encountered. An ideal match would be a cantilever whose suspension was compliant enough to allow the cantilever to do 100% of the deflecting over all groove modulation.
-Steve
Hi Steve,
Me is the guy who sent you the scans of the 1977 AES paper.
Live near Amsterdam, a province of Scandinavia. A bit kidding.I read:
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
When cantilevers are too stiff for the arm mounted, the entire arm deflects as these groove modulations are encountered. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >This will be no problem. Although nothing ever will be perfect in a TT.
When the arm deflects with the groove modulations it will be the case when the input signal(groove modulation is below the resonance frequency. When the resonance frequency is say 10Hz this concerns all groove signals between 10Hz. So the problem only is valid when we are concerned about groove modulations BELOW the resonance frequency.
To evacuate the sound called rubbish (mainly existing below 10Hz we use the problematic situation when we choose to prefer the resonance to be higher than 10Hz. So we use yr problem in the best cases.
Tres bien! (O.K.)I also read:
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
allow the cantilever to do 100% of the deflecting over all groove modulation.
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >When you stick a large piece of cork upon the end of a long thin needle and flex the thing at the empty end as fast as possible, the cork will be in a fixed position.
The incoming signal, the movement of the hand, will be measurable entirely between cork position and hand- position. In the case of the TT, this is the situation for audible incoming groove modulations. They are situated above the resonace ferquency. So the situation is healthy in the described needle- case.
Conclusion: the problem will never arise as long as the input frequencies will be above the resonace frequencies. So fortunately the resonance frequency has to obey one rule: just be below the audible frequencies. A distace between the resonance at 14 Hz and the lowest audible groobve modulation seems very favourable to me.
If it is equal to an audible modulation frequency, still the problem will not yet arise. Moreover: there will be a sensational mplifying experience by the generator- set in yr cart: thanks to the resonance entity.
So there is not much chance that the wish: "compliant enough to allow the cantilever to do 100% of the deflecting over all groove modulation." will not come true.
When will the compliance NOT have the right value in this respect, assuming the total effective mass is constant? That is when the compliance is indeed too stiff. But this will only be the case when the compliance urges yr compliance to be considerably higher than a certain group of audible tones, say from 20 to 22 Hz.
This group will be masked when the resonance is at say 26 Hz, which will guaranty that the mentioned tones will at least not be amplified by the (wide?) resonance area. I suppose only a few hobbyists will ever have encountered such a ultra- high resonavce frequency.
Of which I can assure that it is the lowest limit of the problematic area. So below resonance frequencies of 26 Hz or so, this problem needs not to be feared. I detect rather large safety margin for stiffening the suspension of the stylus suspension. Not very dangerous. In normal cases the compliannce will be sufficient.
Humble but most kind greetings from Bleiswijk, the village with the windmills (and the wooden shoes).
Jan.
I think your position flys in the face of conventional wisdom when it suggests that arm/cart resonant frequencies may be acceptible at 14hz or even above. I am aware that you have been exhaustively arguing this point over on other forums for some time now.The real proof is in the impirical testing. Have you actually tried mounting low compliance cartridges onto low to low/medium mass arms...?
I have seen just how stiff this particular cantilever is. Very little compliance prior to the mod. Particularly in the vertical axis. After the mod, there is visible a moderate amount of compliance in both the vertical and horizontal. Just a moderate amount. Nothing like watching the cantilever of a Shure when mounted to a medium mass arm. All this really adds up to is that the short little cantilever of the Shelter is so stiffly sprung that it, and the arm it is mounted to, will be deflected by groove modulation. The result is a loss of musical information at the least. At the worst, a higher than necessary amount of the, resonances being generated at the stylus groove interface make their way past the cantilever up into the cartridge body and then the arm.
I do not subscribe to your unpopular theory. My own eyes and ears suggest that conventional wisdom prevails.
-Steve
Please, let's seek for a concrete set of theoretic valid considerations which clearly show us that the lowering of resonance frequency by addition of mass to a headshell can be able to improve the sonic reproduction skills of a TT. There must be a backwards- traceable route through physical laws to prove it! I am sure! But untill this moment I never have found it.14Hz is distant enough from the lowest audible groove modulations. I simply do not see the true theoretic relations in this issue. I really like to believe that it sounds better but it more likely seems to be a cure for a mismatch somewhere else.
The better way is to integrate this mass in the stiffness of the arm.
And still I am sure that a resonance at 11 Hz is better for tracking stability than 9 Hz. And 8 Hz is better for tracking stability than 4 Hz. And it will give less BIM.
When the most subchassis- resonances are at 5 Hz I prefer a full distance of one oktave away from that for the resonance frequency. IMHO vibrational disturbance work upwards towards the resonance frequency from an input- signal and not downwards. My natural feeling tells me so. Is it popular to say this? Not necessarily so...
One day a fellow said that the eath was a sphere.... OK, he was not popular.... Never mind.
Jan
This theory is not impopular at all, and your's is not conventional either. This theory is simply not your favourite one. But IMHO the watching of a Shure cartridge has given you the idea, that your eyes and ears can dictate the natural laws to micromechanics.You write:
"All this really adds up to is that the short little cantilever of the Shelter is so stiffly sprung that it, and the arm it is mounted to, will be deflected by groove modulation."
Deflection of the cantilever by groove modulation is the goal of the invention. That never can be bad.IMHO this problem has little to do with compliance and with effective masses. I only can conclude, that the internal resistance of your arm against flexture is too low.
The real problem is not position of the resonance frequency but lack of mechanical stiffness. We simply cannot deny the fact that higher resonance frequencies add less BIM. But arms with relatively low effective mass can still be real sturdy. Perhaps the one you own will not be stiff enough.
We cannot assume that our photographic feelings of dimensional relationships or our ears are able to see, feel or hear tiny flexures or vibrations that will indicate us the accaptabitity of micro- mechanical processes or acceptance of the match of an arm and a cartridge.
But the lack of stiffness or breaking - up entities in an arm, which translates itself by means of glitches in the audible frequency response graph as shown in this AES paper and in some splendid energy graphs in some early HiFi Choice booklets, cannot be faulted to the lack of compliance of a cartridge.
The main causes are some weaknesses in the mechanical properties of the arm. You cannot blaim some splendid research findings for that imho. And let's not blaim a cartridge for the weaknesses of an arm.
There is nothing wrong in a low compliance.
There is nothing wrong in a high compliance.There is nothing wrong in a low effective mass.
There is nothing wrong in a high effective mass.
There is nothing basically wrong in a short cantilever.
There is nothing wrong with the knowledge that higher resonances will give lower BIM.
But some arm designs simply cannot cope so well with larger energy inputs. That is called: mechanical break- up resistance.
Jan.
I'll try this experiment with my Expressimo RB250/103R combo. Other than the cartridge the only differenct is that I have the Mitchell Technoweight and I have the bullet weights to do the HiFi mod. I'm wondering if I can get close to the same numbers without the added weight to the arm.
I intend to give the TWL mod a try quite shortly. However the TWL mod is only concerned about creating a larger moment of enertia while restricting this to the horizontal plane of motion.I was concerned about getting the 14hz reading off the test record during the vertical arm/cart resonance test. This told me I could use some added mass and that I wanted to concentrate this mass primarily to the vertical range of motion. Since adding mass over the headshell adds effective mass to the entire range of motion, it was less than an optimal fix, but it proved to be beneficial nonetheless.
-Steve
It's probably not much perhaps a gram or so but one could calculate it by using the original c/w assembly which yields an effective mass of 12 grams.With the known mass of the original arm and wight of the cartridge you could easily calculate the actual compliance of the cartridge once the resonance frequency is known from the results of the HFN test LP.
Thanks for a post that gives ideas, directions, and a how to for tweeking that little bit more out of the our/my gear. I'm pulling for you to make it through Track 9. I've never even been able to sniff it.
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