Hi,
The tonearm employs the same principle as the old Magnepan Unitrac tonearm, but with modern refinements. The idea of central mass in a unipivot design isn't a new one, but it is a very solid concept.
Here's a bit more on the subject...
http://db.audioasylum.com/cgi/m.mpl?forum=vinyl&n=473487 |
I am very curious on this arm to. Mostly b/c i love lyra cartridges and i assume this arm is really tuned/voiced with lyras in mind. Hope to hear it soon.... |
Both the Centroid and the new-generation Lyra cartridges (Delos and Kleos) were designed partly with each other in mind.
There's the obvious stuff such as working well together and sounding good, but there's another key feature, which is a built-in alignment method that should make life far easier when setting up a new-generation Lyra cartridge in the Centroid.
The headshell of the Centroid has a small hole drilled into it, precisely above where the stylus should be for optimal tracking. The bodies of the Lyra Delos and Kleos have also been drilled so they have a small hole in-line with the stylus location. The holes are sized to accept a 1mm or US 60 gauge (0.040 inch) drill shaft.
The concept is that you pass the blunt end of a 1mm drill shaft through the Centroid headshell and also partly into the body of a Delos or Kleos. This will align the stylus of the Delos/Kleos where it needs to be in the Centroid. Tighten the two 2.6mm JIS mounting screws, remove the drill shaft and the alignment is largely done (smile).
At the recent Munich High-End Audio Show, Stirling Trayle from Immedia brought a Centroid, and we brought a Kleos, and demonstrated the two together. My understanding is that the setup was a 5-minute affair, and that the other people in the room were flabbergasted at how quick and easy the process was.
Allen Perkins and I both believe that while it is important for tonearm and cartridge designers increase the performance potential of their products, it is equally important to make it easier and faster for the user to extract a higher percentage of that performance.
I will quote from the relevant section in the Kleos' manual (the manual includes drawings to make the process easier to understand). I presume that Allen must have a similar section in the Centroid manual.
"Kleos incorporates another, simpler stylus alignment method. The Kleos body has a 1.02mm hole drilled directly above the stylus, and this can be used with compatible tonearms, with a 1mm hole (US 60 gauge or 0.040 inch) drilled through the headshell at the position which gives optimal tracking of the stylus. Obtain a 1mm drill bit (or US 60 gauge or 0.040 inch), and push the dull end into the 1mm headshell hole so that it protrudes by 5~6mm from the headshell underside. Secure drill with clay or putty so that it doesn't slip (but can still move if pushed up vertically). Mount Kleos to headshell so that the protruding drill shaft fits into the 1.02mm hole in the Kleos body. Do this slowly and carefully, since you could scratch the Kleos body if you push or drag when it is not aligned with drill shaft. Once Kleos is flush with the headshell underside, install and tighten the two 2.6mm mounting screws. Feel free to also use a separate template to verify that cantilever is perpendicular to LP groove at null points (normally 66.0 and 120.9 mm from the LP center). Finally, remove drill shaft. This procedure should align stylus to an accuracy of +/-0.3mm."
hth, jonathan carr |
Of course, I consider your Olympos cartridge to be among the finest in the world. That said, in a sense, isn't the alignment similar in ways to the tried and true alignment jig of times gone past? In the case of the Spiral Groove, precision is a given, and Allen's enviable six in-house CNC machines bring the concept to a new level. Still, what interests me most is the inertia concept of the tonearm. I belive, like Jim Winey, that inertia is the singular make or break component of any tonearm.
Regards,
Win
Saskia Turntables |
The concept is that you pass the blunt end of a 1mm drill shaft through the Centroid headshell and also partly into the body of a Delos or Kleos. This will align the stylus of the Delos/Kleos where it needs to be in the Centroid. Cool! I wish all cartridges and tonearms are standardized in such a way and would certainly save so much time for audiophiles. Anyone else has more info regarding the arm design on features that Mosin pointed out such as its dynamic behavior, mass distribution, energy transfer, material, damping, pivot position, etc...? Mr. Perkins is a talented designer and I would like to learn more about his new creation as it, at least, appears to exhibit solid engineering and inventiveness. From the look of it, I suspect the Centroid implemented some of the idea from his earlier design, the Immedia tonearm, which includes novel features like platter level pivot point with adjustable VTA at the bearing spike. The Centroid is probably a further refinement of the Immedia with new idea in handling inertia. Exciting! Also want to know if it uses a secondary bearing to stablize azimuth rocking. _____ |
Haven't heard it but I want one! |
I'm going to try and not be promotional here. If I fail at my attempt, I sincerely apologize. I want to reinforce what Jonathan mentioned about the overhang alignment arrangement when using the Centroid and the new Delos or Kleos. In the case of the Centroid, we include an alignment system that provides exact stylus to pivot positioning of the alignment protractor using the locator hole on the headshell, which will also accommodate for the particular cartridge height (which will change the stylus to pivot point distance) with a height adjustable locator pin mounted on the protractor. When using the new generation Lyra Delos or Kleos, the alignment protractor isn't really needed unless you want to perfectly align the cantilever to the protractor within the deviation of the screw diameter to the headshell slot spacing. Don't get me wrong, zenith is a critical alignment, but I find that visually aligning the cantilever to a protractor is usually only good for a consistent zero point from which to do the final dial in by ear. There is a patent on this locator hole system but the patent is really only to maintain a standard. I know that Allen Perkins invites all cartridge and tonearm manufacturers to use this system in an effort to standardize and make set up easier. Credit must be given to both Jonathan and Allen for their conceiving and executing on this system. It is in the spirit of furthering the art and not market competition. To answer the questions about the Centroid and azimuth stability, the goal was to significantly reduce the moment of inertia and therefor its effect on the cartridge cantilever/suspension system. It is a classic unipivot and the stability goal of the arm is actually in the name. Allen has designed the counterweight to place the center of arm mass at the pivot point (where the pin and jewel cup meet) . In other words, the arm functions on the centroid of the mass. (Centroid; def. - That point about which the static moment of all the elements of area is equal to zero) Of course, the center of mass will move relative to the pivot point depending on the position of the counterweight. The Centroid has a stainless steel counterweight that is quite heavy and wraps closely, forward, and low around the pivot point in such a way that very little movement is required to accommodate a wide cartridge weight/stylus pressure range up front. With the center of mass always located extremely (extremely) close to the pivot point, the moment of inertia is very low and the stability of the system, in all planes is very high...when the stylus is at the record plane. The very low and consistent moment of inertia due to the consistent proximity of the center of mass to the pivot point provides a system that allows for the use of low weight/high compliance and high weight/low compliance cartridges. I'm afraid I've already stepped over the boundries in my explanation so I had best stop here, and I'm sure I've just raised more questions than answered those above. There are a good many details beyond this description that I think are more appropriate for a manufacturer sponsored information site. Again, my apologies of I've come across as promotional.
cheers, Stirling Trayle |
I failed to mention...
Mark Doehmann, Director of Research and Development at Continuum Audio Labs must be noted as well in regards to the concept and discussion that led to the stylus locator hole system mentioned above. I believe Allen, Jonathan, and Mark were sitting around after a trade show chatting about things analog and this was one result. Woulda been fun to sit in on that one... |
Thank you so much for the write up, Mr. Trayle. No apologies needed. That's the kind of info I was looking for and it couldn't be better. You managed to talk about all the design features without lapsing into even one sentence of pornographic sonic description. Bravo! You have no idea how sick I am reading reviews about how "neutral" or "musical" a device is without any analysis of its function and mechanics. Just for that, I applaud you.
The said alignment arrangement is a great idea and I wish more manufacturers can adopt that in the future and, hopefully, it can be standardized among cartridge and tonearm makers. ANYTHING getting the alignment close to the ballpark is better than nothing. All it takes is two tiny holes, one on the headshell and one on cartridge body. Hey, why not!
Thanks for the explanation on the centroid concept applying to the arm pivot. Does the arm still retain the design feature in the Immedia arm like adjusting VTA WITHOUT moving the pivot point? Judging by the picture, the set screw in the middle of the bearing housing appears like such mechanism. I always find that a very unique feature in the Immedia arm, even though the VTA obsessives might complain about the lack of on the fly adjustment - not surprisingly they are usually unipivot users because, I believe, typical (not all) unipivot arms inherently require mass below center of gravity to be stabilized and its pendulum effect can affect VTF, hence sensitive to VTA adjustment. The Centroid concept probably helps in that department. Does it have VTA on the fly adjustment, then? No big deal to me, I rather be listening to records than constantly fuzzing over VTA. Speaking adjustment, how is azimuth adjustment achieved? Another question is damping. Does it have fluid damping like the Immedia or any damping at all?
Don't worry about being promotional. I am sure prospective buyers are more than happy to find out all the design features than not. Your write up is professional, informative and, to me, educational. Thank you for your time.
I am tickled by the story that a bunch talented designers from competing manufacturers sitting around "chatting about things analog" and coming up with ideas that can benefit audiophiles "in the spirit of furthering the art and not market competition." It is this spirit I wish to see more in the forum world.
______
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Hiho, thanks for your comments. Regarding the alignment precision of the stylus locator system described above, I can assure you that it will get you very close. To use your ball park analogy, if the ball park stadium were a bulls eye with the pitching rubber being dead on center, this system will put you on the pitchers mound. From there, cartridge manufacturing variation will require you to find the rubber by ear.
The Centroid does have VTA adjustment, however it cannot be done on the fly. The set screw you see on top of the arm adjusts the the arm body position on the pin of the bearing (and is quite stiff to turn) so adjusting VTA does not alter the pivot point relative to the record plane. The distribution of the mass relative to the pivot point is critical in a unipivot and indeed if distributed incorrectly can exacerbate any resonance or record warp issues the arm has to deal with. For instance, if deliberately disturbed, the Centroid quiets down extremely fast due to the inherently stable nature of the distributed mass and it does not continue to rock. The azimuth is adjusted using a stainless set screw set into the side of the counterweight. The set screw is rather large, is set up high near the pivot point, and buries very deep into the weight . Like the heavy counterweight itself, it requires very little movement back and forth to accommodate any azimuth adjustment required. Damping is provided by using a silicone fluid pool with a variable height set screw to provide a wide range of damping effect, or none at all. On the Centroid model that mates to a Spiral Groove turntable (called the SG Integrated) the fluid pool is integrated (machined) into the arm board and the set screw is threaded into the arm body. For Centroid arms not bound for a Spiral Groove table, the Centroid Universal Integrated arm will have a very lightweight but stiff control plane that simulates the Spiral Groove armboard in function, providing the damping fluid pool, arm rest, mechanical cueing device, anti-skate support, and RCA block. The Universal Integrated is designed to be light enough to be mounted on lightly sprung decks such as the Linn LP 12. The Universal Integrated will mount with a single bolt and will have the facility to adjust the pivot point height to match the record plane of the turntable while still allowing for independent VTA adjustment, albeit it not on the fly. Mounting jigs and tools will be provided to dealers to ensure that the pivot point will be accurately positioned at the record plane of the particular turntable being worked on. The application of anti-skate force can also be a problem for a unipivot. The Centroid anti-skate is applied with a hanging weight connected to the arm body. Where the thread connects to the arm body is height variable so no matter where you have set VTA, you can always position the point at which the anti-skate applies force on the arm is centered at the pivot point and will not tug the cartridge out of azimuth. Additionally, the curve that the string follows is such that it tracks with the variable skating forces across the record and applies an equally variable and therefore uniform anti-skate compensation all the way across the record, which I think is pretty cool. |
As far as i understand the design, forces on the cantilever are minimised during record warps and off center movement. This is controled by mass and not stiffness like in a conventional arm. The arm may look less stable when it tracks a record but when you look more carefully it followes the flow of he groove quite easily. Considering it´s delicate look it is surprisingly long. Effective length is 10.5", a good compromise between accurate tracking agle and stiffness. The materials are carefully chosen including the wiring, the solder and the plugs. Earthing and RFI rejection has been optimised. |
Thanks for the posts here. And I agree no one is being promotional and I appreciate the all the info. What't the best websight for some more detailed pics? |
Hi jfrech,
We have scheduled a photo shoot for the Centroid, but it has yet to take place. No photos yet. Sorry. They will be posted on www.spiral-groove.com when ready. Thanks for asking.
Stirling Trayle
Immedia |
Judging from Stereophile's brief review, the Centroid's design features apparently have been rewarded in sonic terms; two distinct positive characteristics are low noise floor and accurate deep bass. Here's what Brian Damkroger has to say in the review in June 2010 issue. "As I listened more, the characteristics that made the Centroid sound so different became obvious. First and foremost, it had no noise floor - not a dramatically reduced noise floor, but NO noise floor.... A second distinct and obvious characteristic of the Centroid's performance, and one new to me, was how accurately it reproduced the tonal and dynamic elements of deep bass notes." Unipivot arms tend to sound quiet to me so I am not surprised, especially since the Centroid opted for a classic unipivot design with no secondary bearings (the chance of bearing chatter). And quality deep bass is something new in the unipivot genre as it traditionally have a less impactful bass due to the azimuth instability so I have to guess the centroid concept overcomes that. Very promising indeed. _____ |
Is it possible to have the centroid in XLR config?
THanks |
Hello Glai, It shouldn't be a big problem but it would have to be specific to your needs. The current RCA block on the SG Integrated mounts on the integrated Spiral Groove armboard and could not accommodate an XLR pair. The Universal Integrated version is designed to accommodate a lightly sprung turntable design so an integrated XLR block may not be feasible there either. Could a solution that included a longer tonearm wiring harness that terminates into an XLR termination box, which would mount separately from the armboard work for you? Maybe mounted directly on the back of the turntable or on a bracket of some sort that would then mount to the turntable? Or depending on your situation, a strain relief solution that mounts the XLR termination box to the shelf. Have to be very careful moving that one around though.... I'll check it out for you. Maybe you could email me at [email protected] for a more specific conversation. Stirling |
Has anyone used this table with the Ortofon A90? If so how did it preform on it? |
What about Ground connector on the RCA block - I could not see? |
I have been fortunate to have now heard the SG2 with both the Triplanar and the Centriod arm--unfortunately not in the same system. First of all, for those who have not had the pleasure of seeing and hearing the Spiral Groove SG2 it is really something to behold. Purposefully designed, simple to set up and operate yet packed with intelligent engineering. Both the Triplanar and the Centroid seem an excellent match for the SG2 even though they are night and day in terms of design. Both provide exceptional performance on this table. Without being able to compare them in the same system I cannot say which sound I prefer. However, the Centriod struck me as a more simple and elegant design, where the Triplanar provides more in the way of tweaks and adjustments. Both make great music but I preferred the Centriod's engineering and aesthetics. It is quite unique in several design aspects (that make good sense) and simply looks "right" on the table it was designed for. I wish I could provide more in the way of sonic comparison and hope this helps a little. |
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