[Review] Wilson Benesch A.C.T. 25 Tonearm

Let's face it, we all catch the disease from time to time. The uncontrollable (and sometimes irrational) urge to change something in our system. Well it happened to me recently and I am now the proud owner of a Wilson Benesch A.C.T. 25 tonearm. It all started with an email from Pierre Lurné in which he mentioned that the A.C.T. 25 arm was one of a very short list of tonearms that he considered, "... better than the rest". This percolated around in my head for a few weeks and eventually got the best of me. I sold a perfectly good, in fact excellent, Dynavector DV507MK2 and placed an order for the Wilson Benesch arm. The arm was supplied by Red Leaf Audio, the Canadian distributor for Wilson Benesch (WB). The "25" is the latest edition of a uni-pivot/carbon fibre design that WB first produced in the early 90's. A new carbon-nanotube arm, appropriately named the Nanotube One, is about to become available from WB, likely at a much higher price point.

The A.C.T. 25 design certainly can be described as unique and maybe even a bit Star Trekky and this will be the object of some detailed discussion. The installation of this arm also warrants discussion as I am not using the arm on a Wilson Benesch turntable. Of course impressions on how it feels and how it sounds will be discussed at length.

The A.C.T. 25 Design

The WB web site explains that the "25" edition of the A.C.T. arm was named to commemorate the 25th anniversary of the founding of the company in 1989. After a significant amount of time spent trying to find the origin of the name A.C.T. on the Wilson Benesch web site, I gave up. Stereophile magazine says it stands for Advanced Composite Technology, sounds quite plausible to me. The WB site does say that the company was founded with the objective to explore the application of "advanced composites", think carbon fibre. While on the subject, navigating the WB web site turned out to be a bit of a challenge, it does not play well with Chrome or Firefox, much better although still a bit wonky with Microsoft Edge.

We are all familiar with carbon fibre these days as it has become the material of choice for many products such as tennis rackets and golf club shafts. Back in 1989 WB got the idea that this relatively new material was probably a good choice for audio components such as turntables/tonearms and speakers because of its high stiffness, low mass and excellent vibration damping characteristics. Now, pretty much any audio designer will tell you that stiff, light and good vibration damping are excellent characteristics for such audio components so WB was clearly on the right track. Right from the beginning of the company, one of the salient features of the A.C.T. arms has always been the carbon fibre armwand.

The 25 model is no exception with a tapered, carbon fibre, one-piece armwand and headshell. The shape of the armwand/aluminum eggshell is reported to have been optimized for maximum stiffness to weight ratio. A lighter arm means that the mass of the counterweight can be reduced, thus reducing the overall weight (thus Effective Mass) of the tonearm. All good design objectives. The 25 definitely feels light and the fit and finish, to borrow an automotive industry term, is flawless. With respect to its stiffness, we will have to take their word for it as I am not even contemplating trying to put my arm through any torsion tests! The headshell and armwand are a single, continuous piece which is pretty much universally considered to be vibrationally superior to a screw-on headshell. Also, the headshell is designed such that the centre of mass of the cartridge is aligned through the centre-line of the armwand (this has not been confirmed by Wilson Benesch, it was measured "by eye" only). Not only does this make the uni-pivot easier to balance in the lateral axis but it is also important for other reasons. As TNT-Audio's resident tonearm expert Pierre Lurné would say, "... a correctly designed arm aligns cartridge + headshell + tube + bearing housing + rear stub + counterweight along the same general axle". Hopefully Pierre will one day try to write a layman's explanation of this complex subject for our readers.

The pivot design is something that I have never seen before. There is a cut-away photo on the WB web site that shows what's going on in there. It took me a couple of minutes of looking at the image and reading the caption to figure it out! There are 3 balls sitting in a cap with a 4th ball riding on top of them and the arm is riding on top of this 4th ball. There is some tech talk; kinematic bearing (aren't all bearings kinematic?) and high pressure triangulation! Tech talk aside, WB is basically saying that their design eliminates the problem of wear and a resulting chatter that may occur in a uni-pivot of the spike-in-socket design. Again, sound like a reasonable argument to me. Just the detail and complexity of this pivot assembly alone is a convincing argument for the lofty price tag for the 25.

Installation and operation

This section is intended for readers who, like me, plan to install the A.C.T. 25 arm on a non Wilson Benesch turntable. The installation process will be treated in some detail. Installing the arm on a WB turntable is quite easy and there is really nothing to think about, just put it in the socket and tighten a screw. Installing this arm on some other type of turntable definitely requires some thinking and some Do It Yourself skills.

The arm must be mounted on a 217 mm arc from the spindle, however, there are other constraints to consider when mounting this arm on a non Wilson Benesch turntable. I must admit that there were a few nervous moments when I thought to myself "this is not going to work", fortunately, all problems were resolved and I believe that the tonearm will probably fit on most turntables. That being said, some compromise was required and this certainly may be the case for others. Some of the mounting constraints encountered are associated with the arm platform. This is the name given to the carbon fibre platform on which the arm support, the cuing device and the anti-skating post are mounted. The arm platform is fixed solidly to the cylindrical arm base and the anti-skating post is mounted on a point sticking out quite far towards the edge of the platter (see photos).

On my Lenco, there are only small height differences between the top of the platter, the top plate and the plinth. This lack of platter height, compounded with the 12 mm high mounting collar, resulted in the necessity to lower the maple armboard below the level of the plinth, otherwise the arm was too high and out of VTA (vertical tracking angle) adjustment range. Note that in the first photo below, the arm is mounted on a plywood block, this is simply because the WB mounting collar had not arrived yet. The block is the same height as the mounting collar and I simply added a locking screw on the side to secure the arm at the proper height. Referring to the photo, imagine that the arm is mounted farther back on the 217 mm arc. The limit point is where the mounting collar is up to the edge of the maple armboard, thus against the lip of the plinth. The only way around this would be to install the armboard flush with the plinth and let the mounting collar hang over the plinth a bit. This is in fact what is shown in the second photo, however, in order to make this work it was necessary to install a thick acrylic platter (see LencoHell Review) otherwise the VTA adjustment goes out of range as mentioned earlier. The point, let's call it the anti-skating point, ends up over the top plate and the vertical clearance between the two is only a few millimeters. Furthermore the anti-skating weight hangs very close to the platter! It turns out that these modifications allows just enough rotation to have the arm parallel with the side of the plinth. To me this is the most aesthetically pleasing arrangement. Referring to the second photo below, one can see that moving the arm farther back along the 217 mm arc is not possible as the mounting hole would have to be drilled at the junction between top plate and the plinth. Conversely, moving the arm forward so that it sits completely on the maple armboard requires angling the arm inwards so that the anti-skating point clears the platter. The latter scenario would, in fact, have been the Plan-B solution if it wasn't for the use of the LencoHell disk which, as mentioned above, allowed me to raise the arm/armboard.

Installation requires a 30 mm hole over which the WB supplied mounting collar is installed. The collar is held in place by three x 4 mm socket head cap screws which are screwed in from underneath. The supplied cardboard template provides the necessary drilling pattern. In the case where the turntable is mounted on a thick plinth, the standard mounting method may not be possible. Fortunately, my 6 inch thick Lenco plinth has a maple armboard insert so it was relatively easy to install the collar. I simply drilled the armboard to match the template and made a spacer plate of about 8 mm thick to get the arm height in the right range for VTA adjustment. Three holes were then drilled in the spacer plate to accommodate the heads of the cap screws. The arm slips into the collar easily and is held in place by a small socket-head screw. This is also serves as the VTA adjustment. It is important to note that the mounting collar must be stipulated when placing the order for the arm. (an additional $250.) It is not included in the standard package as it is not required for mounting on the Circle 25 turntable. The collar has a flat black finish and blends in fine with the tonearm. It adds about 12 mm (1/2 inch) to the mounting height of the arm which must be taken into consideration.

In the side view photo one can see a small black collar just under the white aluminum pivot housing (the Eggshell). The manual does not explain the purpose of this part but merely stipulates that during the setup process it must be lowered so that it touches the arm platform and tightened in place. While digging around on the WB website I found the manual for the previous models of this tonearm in which the purpose of this collar is explained. When in the up position, it locks the arm so that it doesn't rattle around and damage the pivot bearings during transportation and installation. During the fitting process it was discovered that the tonearm did not work properly if it was lowered all the way down to the point where the arm platform is sitting right on the mounting collar.

For some reason the pivot didn't sit straight and the counterweight range shifted considerably. When I raised the arm a few mm above the mounting collar everything went back to normal. The only possible explanation I have for this would be that the collar to arm platform contact may have been slightly off horizontal. Setting the VTA turned out to be a bit of a challenge. If one loosens the VTA screw without holding the arm up it will drop like a stone. I straddled the Eggshell with my left hand in order to hold up the arm with my thumb and index finger while turning the locking screw with my right hand. For someone with short fingers this definitely could be a problem. Using anything metal such as a screwdriver to hold up the arm platform is a bad idea as it will most probably scratch the carbon fibre.

As mentioned above, after some initial misgivings, I have come to sincerely like the look of this arm. It really does look a bit 21st century but, wait a minute, this is the 21st century! I was surprised to discover that the carbon fibre armwand is very easy to scratch and the scratches are quite visible as they are white against the black of the carbon fibre finish. I discovered this while installing a cartridge. Much to my very great dismay, many cartridges do not have threaded holes for the mounting screws. In the present case, mounting the Denon DL160 cartridge required installing the screws with the heads at the bottom and the nuts on top. I will spare you all of the gory details of this procedure; suffice it to say that just brushing a small tool on the surface of the carbon fibre resulted in a collection of white scratches. Fortunately, I was able to render these scratches almost invisible with the application of a black Sharpie. Why cartridge manufacturers produce such marvels of engineering and then omit such a simple and useful detail such as a tapped hole for the mounting screws is quite beyond my comprehension.

Here are a few more details about operation of the 25 to finish up this section. Like most tonearms, the armrest has a means for holding the arm in place on the post. In this case it is a tiny wire gizmo that rotates on top of the armwand. It looks and feels very flimsy but it does the job. The arm is loose and moves around under the wire but has never come out once locked in. As noted above, the counterweight stays in place due to a spring pin that gives sufficient friction for it not to move around under normal operation. There is no means for holding the counterweight lobes in a horizontal plane, or even an indication of where horizontal is. The lobes can be set horizontal by eye by looking back along the arm while it is on the record. WB writes that the counterweight can be used to fine adjust the cartridge azimuth. In my case, the cartridge azimuth was dead-on so no adjustment of the counterweight off-horizontal was required. The manual states that the anti-skating force can be adjusted in 0.5 gram intervals of cartridge weight! Of course what they meant to say was tracking force not cartridge weight.

The Sound

It is late June, I should be playing golf or sitting on my deck with a beer. Instead I am in my music room listening to Prokofiev. My wife thinks I am, well let's just say eccentric. The A.C.T. 25 has been running every day for weeks, it's like a magnet pulling me to my music room. When it comes to the sound, the 25 does everything well, as good as any I have owned, and it does some things better than many others, notably focus, soundstage definition and channel separation. My speakers don't focus as well as some others that I have owned in the past, the 25 gives them a significant helping hand by providing a more focused source. For the rest, well, everything is there; detail, speed, articulation, dynamics, but more than anything there is an overall feeling of naturalness, the A.C.T.25 is performing a disappearing act. I can't find any single attribute of music playback where I could say that the performance wasn't excellent. My comparables from personal experience would be the Graham 2.2 and the Dynavector 507Mk2, both of which I owned for several years. Of course a direct comparison is impossible as I don't have them any more but I feel quite confident in saying that the WB arm is outperforming both of these predecessors.

The first thing that got my attention was the channel separation and focus. I was listening to the Bruckner Quintet in F Major. (by the way, the Adagio in this piece is wonderful) and the jumps of the sound across the room was quite unexpected. This is a string quintet, not Carlos Santana's band with half a dozen percussionists spread 40 feet across the stage! Violins and violas bouncing the melody back and forth across the small stage is not something one expects to hear and there was a definite "being there" feeling. Also, there are some light pizzicato sections that come through quite clear and detailed even though they are playing in the background. Next I played a Heliodor recording of the Janacek String Quartet. This is a lean recording that sounds like it was made in a room with too much wall absorption and the microphones too far away from the instruments. The sound is too sterile, lacking body and presence. But the 25 makes the best of this limited recording, the cello solos were presented with some body and soul. The star of my classical music listening period was without a doubt the Deutsche Gramophon record of Stravinksy's Ebony Concerto - Dumbarton Oaks, conducted by Pierre Boulez. I am a big Stravinsky fan and I will buy any record I can find that Pierre Boulez is featured on. I never heard anything conducted by Boulez that wasn't excellent. It turns out that this record was actually manufactured at the Polydor K.K. factory in Japan, a factory which had a reputation for excellence. (closed in 1984) This record is in fact absolutely superb and 20th century chamber music à la Stravinsky really shines when played with components that excel in speed and detail. I was so impressed with the sound that I played it 3 times over a period of 2 days.

I decided to play some older records that I hadn't had spinning in a long time. I was right away impressed with the rich and detailed sound from Timbuk3: Eden Alley. I enjoyed this 1980s record very much and listened happily from beginning to end, wanting more. Records such as Marvin Gaye's Greatest Hits and Earth Wind and Fire: I Am were likewise very detailed and more than I remembered. Willie Nelson's Stardust was just beautiful. His unique and wonderful voice on this historic recording was delivered with a perfect gentle precision. Copperhead Road was another pleasant surprise. Like Eden Alley the sound was big, expansive and detailed. This Outlaw-Country/Rock record is known for it's big drum sound and it really filled the room. Another 1980s record that was very well produced and engineered.

Jazz recordings, and I think especially classic jazz recordings, are a very useful evaluation tool for a stereo system. One often finds in these recordings long sustained solo notes, long pauses, soft playing from the rhythm section far off in the background and loud intricate solos. I often use the great jazz artists from the 50's and 60's when evaluating new components. For this review I used Bobby Hutcherson, Joe Henderson, Dave Brubeck, Ron Carter and a few others. The 25 proved to be quite up to the task, very quiet between the notes, possibly something to do with the wiring used but certainly helped by the lack of headshell connector. Solos sounded very natural and effortless and background rhythm play seemed to have taken a more important place in the music. Overall a very impressive and expressive performance of my favorite jazz records.

The soundtrack for the movie Paris Texas featuring Ry Cooder may not be everyone's cup of tea but one thing is certain, anyone who has a good ear will immediately recognize the extremely high quality of the recording. I am speaking here specifically of the vinyl edition as I have not heard the digital version. (if there is one) Played with the Dynavector/A.C.T.25 combination the sound filled the room with beautiful resonating guitar notes.

I have owned the Limited Edition 180 gram set of Esperanza Spalding's Chamber Music Society for many years now. I don't play it very often because it is a torture test for cartridges and tonearms. The combination of big dynamics and Esperanza Spalding's high notes, especially on the first track, Little Fly, has always been too much to handle for my equipment. I have very rarely played this album all the way through because I get annoyed with the tracking issues. I have often wondered if this might just be a bad pressing? One afternoon while adding some final edits to this review, the thought came to me that I should try it. The A.C.T.25/Dynavector XX2-MKII got through the whole record, including Little Fly, without cracking up. On the most difficult notes one can detect that it is right on the edge of the performance envelope but it still delivers music and not noise. A first for my system. As for the rest, well the bass solos are clear and natural, as they need to be, and I am enjoying this record to it's full potential for the first time.

Conclusions

First of all a little housekeeping item. My streak continues, I have found 2 issues in the User's Manual. That being said, the items that I found are certainty considered minor. I still wonder if I will ever find an audio component manual that doesn't have some items that need to be corrected.

Over the years I have owned or installed for others more than 17 tonearms, including several uni-pivot arms including Jelcos and a Graham 2.2. A recent, renewed interest in uni-pivots, mostly as a result of my correspondence with Pierre Lurné, led to a DIY uni-pivot project and the subsequent purchase of the A.C.T. 25. All these experiences can be distilled down into my conclusion that a well designed and well made uni-pivot arm is inherently excellent at channel separation and soundstage definition as well as extracting detail from the grooves. So, I am not at all surprised at the quality of the sound of the A.C.T.25. Space-age materials, a well designed pivot and extreme attention to detail and vibration management, how could it not be good? This arm makes every cartridge I use and every record I play sound as good as or better than it ever has. Isn't that really the essence of the role of a tonearm, don't mess up the source? I will be happy to keep in my system for a long time.

Installation: B+. The A.C.T.25 is not difficult to install and the mounting collar looks good and works fine. However the installation may require some serious thinking before actually getting to the actual execution of the work. In my case, I ended up making 3 armboards before I was satisfied with the result.

Look and Feel: A. After some initial apprehension, I can now say that I like the look of this arm on my Lenco. It works very well, feels quite solid, and is not prone to a lot of flopping around like some uni-pivot arms. You can't handle this the way one could handle something like a Rega RB300, it needs to be treated like the precision instrument that it is.

Performance and Sound: A+. The most important thing that a tonearm has to do is what this one does best. The sound is beautiful, effortless and addicting.

Overall: The design of the A.C.T.25 is at the same time technically very sophisticated and a simple KISS* strategy. The complexity resides in the choice of materials, the optimization of the various components, the design of the pivot bearing and the attention to detail. However the design is stripped down to the essence of a tonearm; a uni-pivot, an armwand and a counterweight. No magnets, dampers, micro-adjustable VTA dials... At first, this might seem to be a strange combination but the more one thinks about it, the more it makes sense. Keep it very simple then apply the best material and engineering possible. This approach has certainly been successful for Wilson Benesch. It's always nice to find a component that lives up to it's reputation.

Music List

DISCLAIMER. TNT-Audio is a 100% independent magazine that neither accepts advertising from companies nor requires readers to register or pay for subscriptions. After publication of reviews, the authors do not retain samples other than on long-term loan for further evaluation or comparison with later-received gear. Hence, all contents are written free of any “editorial” or “advertising” influence, and all reviews in this publication, positive or negative, reflect the independent opinions of their respective authors. TNT-Audio will publish all manufacturer responses, subject to the reviewer's right to reply in turn.

Wilson Benesch A.C.T. 25 Tonearm

Hi-Tech Meets KISS

Introduction

The A.C.T. 25 Design

Installation and operation

The Sound

Conclusions

Music List