Axis 85Article by Udo
Sometimes you come up with an idea that you want to implement, and you immediately start running around telling the world about your plan at the top of your lungs. That’s how we felt after the presentation of the AXT speakers when someone asked us about a wide-range box with a bass supplement. To be completely honest, that was actually the reason for the similarity between the two Axis series built by Patrick Even. So we promised ourselves that we would design a shelf box with the AXT-8 and the AX-5; the initial simulation was very promising. But the dream and the reality are often far apart from each other, and sometimes there are hindrances that have little to do with the plan but cannot be avoided in the end. In any case, the best thing would probably be to start the story of the Axis 85 from the beginning.
It is an old habit of ours, before we start building a loudspeaker, to think about who we could give it to – even though by all appearances, our approach often seems to be the other way around. We are always reminded of the old Hollywood flick, with Doris Day charmingly playing the starring role of a naïve American blonde, where something is launched on the market without choosing anything other than the name – they haven’t even defined the product category. It’s a great comedy, and people might be surprised to hear us say we watched something like that. But movies with comprehensible content have always interested us more than meaningless action. Anyway, back to the plan.
We were sold on the LspCAD, which offered us a reflex volume of just 19 liters for the AXT-8 if we separated out an additional 3 liters from the AX-5. It looked very usable, and its height and width also made it shelf-worthy. So we got to work, using SketchUp to draw a construction plan on the monitor. There was plenty of wood in the cellar, and we cut it quickly ourselves from 22-mm particleboard. We didn’t take any pictures of that step, nor of the subsequent assembly, sanding and routing. But since we have gradually become immune to the sight of the naked OSB, we were no longer very excited about the familiar yellow surface. So we decided to make the wood components a different color. Aside from white, blue is currently still in fashion, and we still had a small package of water-based stain lying around the workshop. We added a quarter liter of warm water from the tap, and we had a colorant that left the slightly recessed surfaces of the OSB unstained. We applied it using one of the many scrub sponges that my wife buys me for doing the dishes. Here we were finally able to put our photographic skills to work.
So far so good, but now the real work began. The second box, still untreated, already measured 1.5 meters in height so that the bass and wide-range speakers could be separated by a crossover. Here it should be mentioned why we are refusing to describe the planned coupling of the two chassis elements as FAST (Full-range And Subwoofer Technology), as the technology was first named by a user of an online forum. A subwoofer is always coupled below 150 Hz, or ideally even much lower, and supports a satellite system that reproduces the entire voicing range. Our project uses more of a traditional three-way box without a tweeter, and with a separation between 300 and 600 Hz. That avoids the big problem with sub-sat sets, where a small bass mid-range speaker is usually dynamically overburdened by the much-too-low separation, while the bass could actually add on another octave but would then unfortunately be locatable. The result is a singer who sounds like he’s lying on the ground, which is not so great for the musical quality. Since the bass and the mid-range speaker are very close together in the Axis 85, a deep transition is not necessary. A useful side effect: the components for the crossover are smaller, so they are correspondingly cheaper and provide better performance. We think a good name for our construction would be the “BLAW” – bass loudspeaker and widrange! It sounds better than “fast,” anyway, which means “almost” in German – in other words, a “not-quite” loudspeaker.
If you have been paying attention to our criticism of the commonly used name, you can probably already guess which unexpected hindrance forced us to scrap all of our plans. A three-way system without a tweeter has to transmit the upper frequencies from a large membrane, which makes the sweet spot very narrow. The solution is positioning the boxes at ear level and also angling them toward the listener. And that’s where the problem comes up, something that only became apparent during the angle measurements: how are we supposed to do those two things with a shelf box that is more than 30 cm deep? Simply taking it off the shelf and putting it on a stand wasn’t a viable solution. The bass amplification from its proximity to the wall was part of the design – otherwise, the 20 liters would be too small for the bass. But because the idea itself was a good one, we didn’t hesitate long. We built a hollow box stand that also expanded the volume of the boxes to about 30 liters. In order to gain access to the bass, we cut out a square in the floor of the shelf, first theoretically in the drawing and then in real life, using a Geat routing template.
The only thing left was to put together the two parts of the cabinet and add a base to keep it from tipping over. The following photos show a simple way to do this.
The second part of the assembly plan is also important – it’s hard to determine the measurements for the glued boards just from the pictures. If you want to measure them yourself, the two assembly plans are of course also available in SketchUp format as a zip file.
[Wood list in 22-mm particleboard per box: front/rear wall/sides; lid/floor; rear chamber wall; chamber floor; Milling depth; base in 22-mm particleboard per box: base; floor]
Since the construction of the Axis 85 turned out to be more complicated than we thought, making the crossover was downright pleasant. We capped the AXT-8 at 200 Hz, which is where the increase started thanks to the baffle-board reflections. That created the beautiful blue curve seen here. The AX-5 was not much harder, even though we were not able to adapt anything from its Quickly or HR crossover. We first altered its green curve in the box at the bottom by soldering an MKP-Q4 (red) into the signal path. At the top, a small air coil with an overlaid resistor reduced the increase above 3 kHZ (blue). The jerkiness of the curve in this area falls within a narrow range and is common for wide-range speakers, so it’s nothing to be concerned about. Overall, the amplitude curve was satisfactory, with an intersection point at 600 Hz and an excellent addition of the branches. In exchange, the bass needed to be connected with reverse polarity against the wide-range speaker. We also gave in to the occasional requests by readers to make their own adjustments, measuring out two other versions for the mid-range and high range.
The doubled resistance through the small air coil cuts the value in half, which adds about 3 dB of volume above 7 kHz and gives the upper range additional freshness in the more heavily insulated space. The second version uses a smaller capacitor to eliminate the fairly wide-range, slight hump between 200 and 1500 Hz, which gives the voices a pleasantly warm tone. The blue version has the advantage when it is set up near the wall, and the red one is better when the boxes are positioned freely. Since capacitors cannot simply be cut down to smaller values but can easily add larger values by connecting them in parallel, we provide a second one in addition to the smaller C. This creates the larger capacity. We reached for the camera again to avoid the last question about how to assemble the crossover and its variations.
Do-it-yourselfers can now unconcernedly start their projects by taking a look at the last photo gallery – for today – showing the installation of the assembly kit components.
Once both of the boxes were finished, it was time to go to the listening room. We couldn’t decide which signal sources to use for our test. We don’t mean to underrate the stereo qualities of the new AV receiver, which we use to listen to the radio every day. But we were certain that our SAC components would give us a better sound; these in turn have something of a price discrepancy with the Axis 85. So in keeping with the good price-performance ratio, we decided on our eXperience KT 88 tube with a clear conscience, knowing full well that only a few do-it-yourselfers will use a tube amp to listen to music. That was also the second problem, because of course we couldn’t focus exclusively on younger customers based merely on the cheaper price of the Axis 85 and the assembly principles. Given the roughly 90 dB of volume, which is quite a bit for boxes with 8 Ohms, we could imagine a few more senior users might also want to enjoy the sound with their record collections and a class A amplifier (or tube). The fact that this involves a completely different kind of music in each case didn’t make the listening test any easier. But what’s the use of complaining? No one is going to believe our sound description anyway. So we put all kinds of CDs into the player, one after the other, and marveled at the boxes’ unusual quality of not really having any unusual qualities. The first thing we grabbed was a two-year-old CD of Bravo hits, where Madonna and Justin Timberlake surprised us with “4 Minutes” and a deep, well-defined bass. Leona Lewis’ voice was clear as she sang to us of “Bleeding Love,” but without any of those feared hissing sounds. When Alicia Keys also failed to disappear into the thundering drums of “No one,” we felt confident enough to recommend the Axis 85 for our younger readers who enjoy this musical genre – although in the absence of appropriately-aged contacts, we haven’t been able to find out whether those names are even still popular.
It was easier for us when we were able to move to the rock, blues and jazz arena, where older box-builders are more commonly found. we weren’t able to keep the volume down on the old Canned Heat classic “On the Road Again,” this time in the original rather than the cover by Katie Melua. The boxes kept up a danceable volume level without any complaints or noticeable effort, giving Udos old bones a good shaking. Even in this very active listening room, there was no sign of a three-way box with a missing tweeter. However, we only really noticed the three-dimensional stage, with the singer out in front with the boxes and the solo guitar grouped behind them with the rest of the band, when we listened to the grandiose “Fried Hockey Boogie” from a seated position more appropriate to some peoples age. By the time we heard the spectacular “Tutu” by Miles Davis without feeling an impulse to give the job to another, more capable box, there was no longer any reason to dissuade the gray-haired generation from trying out the Axis. “Perfect Way,” another track we tried out, was a perfect description.
The classical segment was calmer, but by no means boring. Bach’s Mass in H minor, played on an LP by the Tübingen Kantaten Choir, showed off the room representation that is often used to describe the wide-range speakers. It was easy to imagine that there were no speaker boxes involved at all. As a caveat, not to be overlooked in our enjoyment of the successful project, we should mention that the position of the Axis is very important here. They are most fun when angled toward the listener, but not pointing directly at the listener’s ears. The problem is that you can only share this pleasure with others if you give up the best listening spot, either voluntarily or under duress.