Breakdown of Turntable Performance

Over the years I've read numerous reviews of turntables, arms, platters, and plinths.  I always wondered how much these individual components contributed to the overall sound.  Here's my take:
Cartridge - 80%
Arm - 10%
Platter - 5%
Plinth - 5%
Some would say pretty much the exact opposite.  Platter/plinth most important, arm second, cartridge last.  Depends on who you ask I guess. 
But when you think about it - the plinth and platter need to be designed to be immune to feedback and turn the record at the proper speed.  The arm must be designed so as to extract the maximum info from the cartridge.  Many feel a better arm and cheaper cart work better than the opposite.
Ideally it should be:
Cartridge 100%
Arm, Platter and Plinth 0%

With the very best tables and arms I would say:
Cartridge 90%
Arm 4%
Platter 1%
Plinth 1%
Outside influences 4%

With a typical mid Fi table:
Cartridge 70%
Arm 10%
Platter 4%
Plinth 12%
Outside influences 4%
For what it's worth, I recently had a $385 cartridge sound much better than a $1200  one that I have. With the turntables I have had, the arm and platter bearing made the biggest differences. YMMV.
Everything is built on a foundation. If anything below the seperate stages of each individual stage is comprimised then EVERYTHING above it is multiplied increasingly.
Self noise from motors not mentioned here in my experience do far more harm.
Its a weakest link scenario regardless of personal bias . Cause and effect...they all matter equally in the bigger picture...
I'd start with a tt's ability to have it's platter effectivly isolated from its bearing.
A $50 AT95E cartridge on my Music Hall MMF 7.1 sounded better than a $800 Clearaudio Virtuoso Wood on my Music Hall MMF 2.2 table.  Better feet, a more solid plinth, a detached motor, a better tonearm, better wiring... those things all matter. 

Where it especially makes a difference is in the bass, but also throughout the entire range.  No matter what mods I've made to the 2.2 or what cartridge I put on it, the bass has that "cardboard" sound (I don't know a better way to describe it) while it is very solid and tight on the 7.1.  The cheaper turntable just doesn't have the same level of vibration isolation and it's apparent in the sound.

A cartridge can perhaps have more impact on the character of the turntable's sound much like speakers do, but much like your entire system, if you have a sub-par source, amp, and/or preamp ahead of the speakers, they may sound different, but not as good as lesser speakers would with better electronics in front of them.  

If I had a $1000 budget I'd rather have a $700 table with a $300 cartridge than a $300 table with a $700 cartridge.
A cheap/effective alternative to all of this is a proper platter mat.

The MyMat is quite possibly the most effective cure for most tt ills. Read a review on "What’s on your turntable tonight" thread.
The amplitude portion of the musical waveform comes from the cartridge, but the frequency portion, the time element of that waveform, comes from the turntable. The most important characteristics for a turntable are stable speed accuracy and low noise. If you want to talk about turntable construction, pay attention to the motor, controller mechanism, bearing and their implementation.

The tonearm must hold the cartridge in the correct three dimensional alignment with proper down force to allow the cartridge to extract maximal information from the groove wih minimal distortion.

Without these elements you won’t get what you paid for from whatever cartridge you have

I am running a cart that cost me $150 on a $3200 table/ arm .
Nuts right?
It's all about synergy, you just cannot make any reliable call on this type of thing.

And as a beta tester of Slaws MyMat I can attest to the veracity of his statement.
Anyone is free to pm myself for more detail about the results.
But much improved Dynamics and tightness of bass are easily audible.
For me it really opened up the upper registers.
Obviously ymmv.
Fellows, I tried finding the Slaws My Mat, and couldn't. Can you direct me on where to find them?

They are made by member Slaw.
Just send him a message through the Audiogon system.
Hope that helps

Hey, It's my product and was just beta testing it. I don't have a site but would love to have you PM me with any questions.
@chayro said it well, but I would be more emphatic. I tried it like the OP said, and burned mucho $ before I realized that cartridges wear out. TT not so much.

And how the **** is a $100 No-name Garbage tonearm going to hold a $5K Koetsu in precise relation to the record surface? Especially when that record surface is vibrating all over the place because of the No-name Garbage platter turning on a $.05 bearing? Powered by a lawnmower motor? 
And how the **** is a $100 No-name Garbage tonearm going to hold a $5K Koetsu in precise relation to the record surface? Especially when that record surface is vibrating all over the place because of the No-name Garbage platter turning on a $.05 bearing? Powered by a lawnmower motor?
Oh so you have seen my rig Terry!
Briggs & Stratton is the best brand......
I've obtained great results by isolating all 5 major components from each other. The controller, motor, flywheel, turntable, & arm pedestal, are all on there own platforms. Isolation & quality parts are key. BTW I can attest to Slaw's MyMat being well worth the investment. It is the best I've had on my table.   
Arm: 33.33%

Cartridge: 33.33% 

Table: 33.33%


Pressing quality: 50%

Everything else: 50%

The requirements for the turntable depend on quality of the cartridge it has to serve.  I was very happy with my at-lp1240 til I had my AKG P8ES Supernova upgraded with a boron cantilever.  The upgrade made a huge difference in responsiveness, but the byproduct was the direct drive motor noise became much more noticeable once the stylus hit the vinyl.  It wasn't a problem for me before.  I'm now looking for a belt driven turntable so I can enjoy the cartridge more.
My brain can only grasp what sounds good to my ears.  I have a 30+ year old Technics SL-1600MK2 with Ortofon Blue in my rec room and a one year old Technics SL-1200G with Ortofon Quintet Black in my listening room.

At first, I had the Blue on the 1200G.  It sounded pretty good.  I then bought the Black.  All other things being equal (record, phono preamp, etc.), I'm sure I don't have to tell you which one sounds waaaaaay better.
All this turntable talk and no love for the Well Tempered concept?
Chatter-free viscous damped platter bearing, chatter-free viscous damped tonearm bearing, physically isolated motor?  WT has 'em all.  I bought the original WTT/TA in 1988 after owning an LP12, a Technics SP-12 w/AT tonearm, and a SOTA Sapphire with a Premier FT3.  I found it to be superior to all of them in quiet no-stress sound and operation, incredibly static-free in the dry months, and have never even thought of replacing it.  I now run a vintage Grace F9 Ruby with low hours in it after using a van Den Hul MC10 for most of its life.  Look into their Amadeus.
The OP asked about relative IMPORTANCE, and most guys responded with a COST analysis.  That's just one reason why the question is so complex. On a cost basis, I have often found that a very fine turntable and exceptional tonearm can bring out unexpected qualities of a relatively inexpensive cartridge, but that's where the complexity of the question enters into it.  If the inexpensive cartridge can sound so good, it is also an indication of how poor is the correlation between cost and performance, for phono cartridges.  If you leave out cost, all 3 components have to work well together, else you will never get the most out of the cartridge.  So, I don't know how anyone can say that the cartridge is vastly more important than the tonearm and turntable. (The OP says "80%" for the cartridge. Some others estimate an even higher percentage contribution from the cartridge.)  Cartridges fall right on their faces without the contributions from turntable and tonearm.
 Here's my take:
Cartridge - 80%
Arm - 10%
Platter - 5%
Plinth - 5%

No love for the bearing? Interesting. The motor I guess is optional equipment too. Probably since the bearing and motor are zero you could just scrape the cartridge by hand. I mean after all that is where almost all the sound comes from. Save a lot of money that way!

Still, fascinating subject. Back in the day we had this thing we all did, it was called changing only one thing at a time. Idea being, if you change a bunch of stuff you just can't know what did what. So we ran around changing only the speakers, and when we heard a system with new speakers and everything else in the system was new too we'd say the system sounded good or maybe that the speakers might be pretty good but they were with all this other stuff we need to hear them again to be sure. By again we meant with all known associated equipment.

Man what a waste of time! We shoulda made one of these lists! Then we could just leave all that other stuff off the list and BAM! Speakers 80%! Yeah, science!

Yeah, sarcasm. Makes the point. What are the odds you're gonna get the percentages right, when you can't even come up with all the things that belong on the list? No bearing, no motor. Also no mass, nor suspension, which if you don't have an awful lot of one you sure need the other. Linn, ring a bell? Also nothing to control the speed of the motor. Power? Zero. Good luck with that!

But even with a full list, how can you even begin to assign percentages? The normal, established, and accepted approach is to carefully change only one thing at a time. That's why we bring stuff home, to see how each individual thing sounds all by itself when added to our system. With turntables then, in order to have any idea at all, you would at a minimum need to change each individual component part, one at a time.

So let's see now.... the first one I did was the belt. Just the belt. Tried a couple different ones. Then the power cord going into the motor. Soldered another one to it. Then the motor itself. Then tried a different motor controller. Then tried the different motor controller with battery power. Hey, I know! Let's make a list!

Bearing: took it apart, changed teflon coated bronze thrust plate for tungsten carbide; changed stainless ball bearing to silicon carbide. Polished bearing shaft to 4 micron finish.

Platter: compared exact same dimensions platters in solid acrylic, lead shot weighted acrylic, a proprietary composite material, and stabilized and weighted Cocobolo.

Plinth: compared several in MDF, and carbon fiber, of different construction and mass, including BDR Shelf.

Shelf/rack: tested a whole range of these, everything from none (sitting right on the floor) to MDF (various shapes and thicknesses), to sand and concrete and granite and carbon fiber and sorbothane and even a few others we will zero off the list because you get the point. I hope.

The rack, or whatever the table sits on, is just as much a part of it as anything else. What is the question again? Oh yeah: Breakdown of turntable performance. If there's one thing I know its that the rack or whatever the darn thing sits on instantly becomes an integral component of turntable performance.

We report. You decide.

What's funny is that in spite of having done all those comparisons and knowing intimately and well exactly the contribution of each part the last thing I would ever do is rank them top to bottom, let alone assign percentages. If forced, if you held my hand to the flame, I'd say they are all equal. 

Because if there's one thing I have learned from changing all these things its that every single little thing matters- and none more so than any of the others. But hey, lists are fun. Pretending is fun. Who knows, every once in a while could maybe even lead to learning a little something new.

I must say I find all debates such as this one amusing/interesting from a couple of perspectives.  Most importantly, any "system", not just hifi, can only perform as well as its weakest link.  Not a single component in these systems is without imperfections/distortions.  Those of us who enjoy this "hobby" are all guilty, at one time or another, a seeking some "tweak", but in doing so, often are "losing the forest through the trees." to debate percentages, such as has been done above strikes me as funny, as, in the end, the sound we all perceive is somewhat subjective, anyway.  By analogy, if I may, one can create a delicious meal using less than the worlds best ingredients, though some may enjoy it more than others.  On the other hand, one lousy substitution or the like, in that recipe, and the meal won't be nearly as good, though there might STILL be someone who thinks it is delicious.  I would imagine that components at the from end ultimately are the most critical, beginning with the source material, especially with analog/LPs....
I would say its the table, then the arm, and finally the cartridge.  The cartridge I think affects the color of the music the most, but you will not get there for some cartridges without a decent turntable and arm setup.
This is like the "which organ is the most important in the body" question. The a..hole almost won. 😀
I have all of them. I like Aiwa PL-3000 . It can scan any track in any order. Very rare turntable.
As said somewhere above, the function of the motor and platter is to rotate the record at a constant rate, inaudibly. Other "contributions" (e.g., resonance) from platter, motor, and plinth could be viewed as defects rather than assets so ideally should be zero. The same is true of turntable support.  Once that is accomplished the rest is up to the tonearm and cartridge, correct compliance matching, and setup.  And of course the condition of the record.

Many years ago I attended a demonstration by Linn. They had two Identical Linn Sondeks, one fitted with their previous top tonearm the Ittok. The second sondek was fitted with the more expensive Ekos tonearm. to emphasise the tonearm's contribution relative to the cartridge, the Sondek/Ittok was fitted with their top mc, the 'Troika'. The Sondek/Ekos was fitted with their budget K9 mm. The cost of the Ittok/Troika and Ekos/K9 were similar so it wasn't a question of spending more money but simply what priority to give to the arm or pickup. Anyway, the majority consensus was the the Ekos fitted with the cheap K9 was sonically the winner! The Ittok/Troika was a tad more 'polished' in the treble and a bit more extended in the bass. The Ekos/K9 was superior in sound-staging, Imaging, dynamics, etc etc.

Spindoctor, That has been my experience with arms as well. The thing is... That more expensive cart on the more expensive arm (Ekos) would have brought things to an entirely higher level. It all matters. 
That's interesting, i would have bet money the Ekos/K9 rig would have better bass than Ittok/Troika one
Personally, I believe your playback is as strong as the weakest link. There is no perfect equipment . . . otherwise, there would come a time when no improvements and the industry would come to a point where their “new models” would cease. Think about it, this is never going to happen, because it would be like all disease and aging were eliminated -- how many medical and pharmaceutical companies would go out of business? You do not cut off your nose to spite your face . . . at least not among the wise and intelligent.

Let's face it, the tweaking and the updating is part of the charm and frustration of the hobby. Without it, hobbyists would have to seek another hobby to satisfy that endeavor. Contentment, as is the case with those with LIMITED wallets, would have to become a mental acceptance that there is no more updates or improvements to be had . . . perhaps all that would be left to do would be to replace that which would wear out or got damaged.
All... I've updated my ad for MyMat.

Here's the main thing....Turntable manufacturers have a big hurdle to overcome when using a mechanical bearing. This is trying to keep the bearing' vibration (no way to overcome this with a mechanical bearing) from reaching the platter. In addition, just in the act of playing a record, the stylus is vibrating. These two BIG issues keep us from hearing a turntables ultimate performance. The easiest way to solve these two big problems is with an effective platter mat. I've developed one. Check out my revised ad on USAM. If you respond to this ad, I can answer any questions and take care of any order.

Happy Listening!
Regarding an analog rig (tt,arm,cart)... what's the weakest link?

It's the ability of any tt manufacturer to isolate a mechanical bearing from reaching the platter...IE: the lp!

MyMat is the most cost-effective solution to take care of this.