help with arm types

can anyone tell me the different arm types available, and their advantages/disadvantages?

i have a expressimo rega 250 arm, and am considering an upgrade (along with my cartridge). i know the arm/cartridge synergy is important, and want to make the right choice. the cartridges on my short list are an urushi or a shelter 501 or 901.

priorities include ease of use and "set it/forget it".

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There are several different arm types available, and they can all be good. They may have some different strengths and weaknesses, and some are good enough to have mostly overcome any "categorical" weaknesses that may be attributed to the basic design concepts of the arm category they belong to.

Basic unipivot - A single point bearing system, which generally is quite unstable when cueing, but becomes much more stable when playing the record. There may still be some level of instability present when faced with low compliance cartridges. Main advantage is typically a liquid sounding midrange and effortless sounding presentation. Bass is sometimes weak sounding.

Improved unipivot - Some unipivots provide "outriggers" or other forms of stabilizers to counter the inherent instability of the basic unipivot design. These can be top quality sounding arms, and may handle low compliance cartridges satisfactorily. Advantages are as above like the basic unipivot, but with less or none of the disadvantages, depending upon the design. Graham 2.2 is probably the best known and respected of this type. This type is currently quite popular in sales.

Gimbal bearing - Uses a dual axis bearing system employing precision adjusted bearings such as ball races. Has much higher inherent stability than a basic unipivot, but may suffer from bearing chatter in the lower quality or lower price models. Advantages include good overall stability when using lower compliance cartridges. Bass response is usually good. Sometimes they may sound more mechanical or less effortless than a good unipivot, and less liquid in the mids. SME V is probably one of the best known of these types.

Linear tracking - Uses an air bearing or mechanical system to allow the tonearm to track tangentially to the record groove. Has alot of potential for excellent sound quality because of this. However, the expense and complexity of certain designs may make them very expensive. The lower priced models may suffer from maladies that make them sound less good than lower priced pivot arms. Sound quality can be effortless and liquid like the best unipivots, and have the stability and the bass response of the best gimbal bearing arms. The most expensive and highly regarded arms in the world are typically linear tracking air bearing type arms. Eminent Technology ET2.5, Walker,AirTangent, and Rockport are well known arms of this type.

There are some other types such as knife-edge bearing, and dual pivot, and hanging tonearms. These are relatively rare types of arms, but they can be good if designed well. SME 3012 is a knife edge, Morch DP-6 is a dual pivot, and Schroder and Well-Tempered are hanging types of arms. These arms are well regarded, so they can be considered among the better or best arms, even though they use some less conventional designs.

These descriptions are quite general, and may be more or less applicable to any given brand of arm. I do not intend to disparage or hype any one type of technology, but just want to give some basic ideas of the major categories and their typical strengths and limitations.

The best arms in all these categories can transcend the basic limitations of the simple designs, and can be world class arms. Many other things play into this equation, such as materials resonance, construction quality, rigidity, wiring, geometry, etc.

The best thing to do is audition the arms with good reputations in their price ranges that you can afford, and consider the synergy of the table and cartridge that you plan to use. The arm is not working alone, and needs to be considered in a system context with the appropriate table and appropriate cartridges. This is the only way you can get proper results from your package.

As usual, your response is such a great resource. Thanks, I really appreciate it.

As you know, since you've helped me set it up, I have a Teres 245, with an expressimo/denon 103r, and I've thoroughly enjoyed myself. There is something indescribable about the sound, that I love so much.

I know you've recommended the Origin arms before, paired with the Shelter cartridges. I believe the Urushi is similar to the Shelter, in terms of mass and compliance requirements? Are there other arms to consider, beside Origin's?

The Origin's would have to be bought new, as they are almost never on the used market, whereas maybe I could find another arm, that is just as good or better, on the used market, for the same or less?
Dennis, I'd add to what Twl wrote except that I can't. As usual he summarized everything very well.

That's a pretty nice cartridge shortlist. They're all relatively low in compliance, keep that in mind when thinking about arm types. Check my system for one combo that works very well. I'm sure the higher model arms from OL would work even better.

"Set it and forget it"? Did you want the digital forum?!
hey doug... i actually consider my expressimo/denon 103r "set it, and forget it"... I spent a fair amount of time being picky making sure everything was right, and i've checked everything once since then, and other than VTA, i haven't had to adjust anything. i re-checked the tracking force, arm placement, cartridge angle, leveling, etc. once since my initial setup, and nothing really needed adjusting.

of course everything sounded great, but i thought that maybe my hearing wasn't sensitive enough, what did i know?

i then got nervous that this couldn't be right, that setting up and maintaining the turntable had to be harder, and i bought the "test" LP (forgetting the name off the top of my head... HiFi magazine puts it out?), that tests everything from phase, to tracking, and all tested really well. i was able to get through all but one of the tracking tests... and passed all the other tests with flying colors.

Just joking about the digital thing of course, though with such a nice rig you already knew that! One of the good things about the OL arms, much like yours, is that there AREN'T a lot of dials and buttons to fuss with. Get the setup right, lock it down, play music. If you go with OL buy from a reputable dealer. OL has occasional Q/C lapses so you want to be able to return if necessary.

The HFN test record is kind of fun to play with, but not all that useful in the end. Your ears quickly become a better judge of whether your setup is right or not. FWIW my 265/OL Silver/Shelter 901 perform about the same as yours: no real buzzing until track 4, pass all other tests, horizontal resonance about 10.5Hz, vertical resonance about 11 Hz but almost nonexistent.

Last week I had to realign my arm/cart because a certain partner apparently nudged the armboard a mm or so. All of a sudden I was hearing inner groove distortion on records that never had it before. So I dragged out the protractor, the magnifier, the shiny bright light, the muttered curses... When I spun up the first side we listened for a few minutes and he asked, "Did you change the antiskate setting?" Sure enough, I'd dropped it to zero to use the protractor and forgot to reset it. Who needs test records?!
I would just like to say a great big 'thank you' to Tom for giving a brief but concise summary of the different arm types and their respective strengths and weaknesses.

I was just wondering whether Tom or any other members hee could add perhaps a short list of any applicable do's and dont's for each arm type, e.g. I've heard it mentioned that unipivots should not be installed on tables with a suspended design, etc.